Focus on California Life Science 7th Grade Unit 2 - Chapter 6 Modern Genetics

' Chapter Modern Genetics A Stan Preview A typical cell of any ism contains genetic instructions that specify its traits . Those traits may be modified by tal influences . As a basis for understanding this concept . Students know sexual duction produces offspring that inherit half their genes from each parent Framework Mitochondria DNA is derived solely from the mother , making possible the tracing of heritage from grandmothers to dren with great certainty . Students know an inherited trait can be determined by one or more genes . Students know plant and mal cells contain many sands of different genes and typically have two copies of every gene . The two copies ( or alleles ) of the gene may or may not be identical , and one may be dominant in ing the phenotype while the other is recessive . Students know DNA ( acid ) is the genetic material of living organisms and is located in the somes of each cell . The members of this family resemble one another because they share some alleles . 186

. Modern Genetics Focus on the BIG Idea How are traits inherited in people ?

Check What You Know Suppose you have a friend who does have freckles . Both of her biological parents have freckles . The allele for freckles is dominant . What can you infer about the genotype of your friend parents ?

Explain your answer . Chapter 187 The images shown here represent some of the Key Terms in this chapter . You can use this vocabulary skill to help you understand the meaning of some Key Terms in this chapter . Academic Words academic words are words that are used frequently in classrooms . You and your teachers use these words when you discuss the subjects you study . Look for the words In the table below as you read this chapter . Example Sentence normal . Usual , typical , Its normal to feel nervous a bout ( expected going to a new school . 200 structure The way in which Vou have learned the basic ( parts of something are structure of plant and animal 200 connected ce To influence to Scientists are looking for ways to produce a change in treat diseases that people , technique A special way of There are special ues for ( tek ) doing something , a balancing on a skateboard . 206 method , a procedure Apply It ! Choose the word that best completes each sentence . People diets can their health . in

Chapter Vocabulary Section ( page 192 ) multiple alleles sex chromosomes gene carrier Section ( page 199 ) genetic disorder pedigree karyotype Section ( page 105 ) selective breeding inbreeding hybridization clone genetic engineering gene therapy genome ) Build Science Vocabulary Online Visit . om Web Code Chapter 189

to coding Skill Identify Main Ideas The main idea in a paragraph or section is the most . Sometimes the main idea is stated directly in a sentence . Other times you have to figure it out on your own . The boldfaced Key Concept statements can help you identify main ideas . The details in a paragraph or section support the main idea . Details are usually specific facts and examples that help readers understand the main idea . Look for the main idea and details in the paragraph below . In human inheritance , there is not always a relationship between gene and trait . For example , some traits , such as blood type , are controlled by genes with more than two alleles . Other traits , such as height , are controlled by many genes that act together to produce the trait . After you have read the paragraph , copy the graphic organizer below . Complete it by filling in the main idea and missing detail . Apply It ! Use your graphic organizer to answer the following questions . What is the main idea of the paragraph ?

What details support the main idea ?

I Standards Investigation Teach Others About a Trait People inherit alleles for traits from their parents . Some traits , such as keen eyesight , are beneficial . Other traits , such as , can present challenges . In this investigation , you will design a display to help teach younger children about a genetically inherited trait . You and your group will need to research the inheritance pattern of your selected trait . Your Goal To design and build an educational tool or display about genetically inherited traits that can be used to educate young children The display you create should illustrate how the trait is inherited and whom it can affect explain whether the trait is dominant , recessive , or codominant contain an interactive question and answer section that includes a way of predicting the probability that a person will inherit the trait stand by itself and be easy to set up Plan It ! Begin by choosing a trait and researching its inheritance pattern . Then determine how the display will look and the materials you need . Determine what is the best method to make the display interactive . Plan to test your display on a younger audience to assess their understanding and then revise your design . Chapter 191

A typical cell of any organism contains genetic instructions that specify its traits . Those traits may be modified by environmental influences . Students know an inherited trait can be determined by one or more genes . What are some patterns of inheritance in humans ?

What are the functions of the sex chromosomes ?

What is the relationship between genes and the environment ?

Key Terms ' multiple alleles sex chromosomes gene carrier FIGURE Family Resemblance Because children inherit alleles for traits from their mother and father . children often look like their parents . 192 Human Inheritance Standards How Tall Is Tall ?

Choose a partner . Measure each height to the nearest centimeters . Record your measurements on the chalkboard . Create a bar graph showing the number of students at each height . Plot the heights on the horizontal axis and the number of students on the vertical axis . Think It Over Inferring Do you think height in humans is controlled by a single gene , as it is in peas ?

Explain your answer . The arrival of a baby is a happy event . Eagerly . the parents and grandparents gather around to admire the newborn baby . Do you think she looks like her father ?

Yes . but she has her mothers eyes . When a baby is born . the parents , their families . and their friends try to determine whom the baby resembles . Chances are good that the baby will look a little bit like both parents . That is because both parents pass alleles for traits on to their offspring .

, Patterns of Human Inheritance When Mendel experimented with peas , he studied traits that were controlled by genes with one dominant allele and one recessive allele . The inheritance of traits is rarely this simple . A single gene can have more than two alleles , or more than one gene can be involved . Sometimes , a single gene can affect more than one trait . Or , all of a gene effects may not be visible or even known . Because patterns of inheritance can be , there is not always a correspondence between trait and gene . In this section , you will learn about some patterns of human inheritance . Some human traits are controlled by single genes with two alleles , and others by single genes with multiple alleles . Still other traits are controlled by many genes that act together . Single Genes With Mo Alleles Several human traits are controlled by a single gene with one dominant allele and one recessive allele . These human traits have two distinctly ent , or physical appearances . Whether your earlobes are free or attached is a trait trolled by a single gene with two alleles . A widow peak is another . A widow peak is a hairline that comes to a point in the middle of the forehead . The allele for a widow peak is nant over the allele for a straight hairline . The square in Figure illustrates a cross between two parents who are zygous for a widow peak . Notice that each child has a in , or 75 percent , probability of having a widow peak . There is only a in , or 25 percent , probability that a child will have a straight hairline . When Mendel crossed peas that were heterozygous for a trait , he obtained similar percentages in the offspring . FIGURE widow Peak Square This square shows a cross between two parents with widow peaks . Interpreting Diagrams What are the possible of the offspring ?

What percentage of the offspring will have each genotype ?

Chapter 193 FIGURE Inheritance of Blood Type Blood type is determined by a single gene with three alleles . This chart shows which combinations of alleles result in each blood type . Alleles of Blood iy Combination , WA or i ! or lei FIGURE Many Skin color in humans is determined by three or more genes . Different combinations of alleles for each of the genes result in a wide range of possible skin colors . Single Genes With Multiple Alleles Some human traits are controlled by a single gene that has more than two alleles . Such a gene is said to have multiple or more forms of a gene that code for a single trait Even though a gene may have multiple alleles , a person can carry only two of those alleles . This is because chromosomes exist in pairs . Each some in a pair carries only one allele for each gene . Human blood type is controlled by a gene with multiple alleles , as shown in Figure . There are four main blood , AB , and . Three alleles control the inheritance of blood types . The alleles for blood types A and are nant . The allele for blood type A is written as IA . The allele for blood type is written 15 . The allele for blood type ( recessive . Recall that when two codominant alleles are inherited , neither allele is masked . A person who inherits an allele from one parent and an 15 allele from the other parent will have type AB blood . Only people who inherit two i alleles have type blood . Traits Controlled by Many Genes If you completed the Standards activity , you saw that height in humans has more than two distinct . In fact , there is an enormous variety of for height . Some human traits show a large number of because the traits are trolled by many genes . The genes act together as a group to produce a single trait . At least four genes control height in humans , so there are many possible combinations of genes and alleles . Skin , eye , and hair color are other human traits that are controlled by multiple genes . Holding why do some traits exhibit a large number of )

Daughter The Sex Chromosomes The sex chromosomes are one of the 23 pairs of chromosomes in each body cell . The sex chromosomes carry genes that determine whether a person is male or female . They also carry genes that determine other traits . Girl or Boy ?

The sex chromosomes are the only chromosome pair that do not always match . If you are a girl , your two sex chromosomes match . The two chromosomes are called chromosomes . If you are a boy , your sex chromosomes do not match . One of them is an chromosome , and the other is a . The is much smaller than the chromosome , as you can see in Figure . Sex Chromosomes and Fertilization What happens to the sex chromosomes when egg and sperm cells form ?

Since both of a female sex chromosomes are chromosomes , all eggs carry one chromosome , Males , however , have two ferent sex chromosomes . Therefore , half of a male sperm cells carry an chromosome , while half carry a chromosome . When a sperm cell with an chromosome fertilizes an egg , the egg has two chromosomes . The fertilized egg will develop into a girl . When a sperm with a chromosome an eg , the egg has one chromosome and one chromosome . The egg will develop into a boy . FIGURE Male or Female ?

As this square shows , there is a 50 percent probability that a child will be a girl and a 50 percent probability that a child will be a boy . Interpreting Diagrams What sex will the child be ifa sperm with a chromosome fertilizes an egg ?

Chapter 195 For Links on genetics Visit Web Code Normal vision Genes The genes for some human traits are carried on the sex chromosomes . Genes on the and chromosomes are often called genes because their alleles are passed from parent to child on a sex chromosome . Traits controlled by genes are called traits . One trait is . A person with this trait can not distinguish between red and green . Recall that females have two chromosomes , whereas males have one chromosome and one chromosome . Unlike most chromosome pairs , the and have different genes . Most of the genes on the chromosome are not on the chromosome . Therefore , an allele on an chromosome may have no corresponding allele on a chromosome . Like other genes , genes can have dominant and recessive alleles . In females , a dominant allele on one some will mask a recessive allele on the other chromosome . But in males , there is usually no matching allele on the chromosome to mask the allele on the . As a result , any allele on the a recessive produce the trait in a male who inherits it . Because males have only one chromosome , males are much more likely than females to have a trait that is controlled by a recessive allele . FIGURE The lower photo shows how a red barn and green look to a person with . 1960 colorblind vision

is a trait controlled by a recessive allele on the . Many is In luv . Activity A more males than females have can understand why this is the case by examining the square in Figure . Both parents in this example have normal color this activity aka a vision . Notice , however , that the mother is a carrier of test to if you have blindness . A carrier is a person who has one recessive allele for a , ee , trait and one dominant allele . A carrier of a trait controlled by a Take bog at the recessive allele does not have the trait . However , the carrier can below . what do you see ?

can pass the recessive allele on to his or her offspring . In the case of YOU 599 009 the traits . only females can be carriers . the As you can see in Figure , there is a 25 percent probability i uN that this couple will have a colorblind child . Notice that none ' of the couple daughters will be colorblind . On the other hand , the sons have a 50 percent probability of being colorblind . For a female to be colorblind , she must inherit two recessive alleles for , one from each parent . A male needs to inherit only one recessive allele . This is because there is no gene for color vision on the chromosome . Thus . there is no allele that Could mask the recessive allele on the chromosome . What is the sex ofa person who is a carrier for ?

Inferring Based on the results of the test , what is your Fame genotype for this trait ?

normal vision ) El Daughter Son noun ( normal vision ) normal vision ) square is a linked trait . A girl who receives only one recessive allele ( written ) for will not have the trait . However , a boy who receives one recessive allele will be colorblind . Applying Concepts what allele combination would a daughter need to inherit to be colorblind ?

Mother ( carrier ) 197 The Effect of Environment In humans and other organisms , the effects of genes are often by an environment . Many of an organism characteristics are determined by an interaction between genes and the environment . You have learned that several genes work together to help determine human height . However . people heights are also by their environments . For example . people diets can affect their height . A diet lacking in protein , certain minerals . or certain vitamins can prevent a person from growing as tall as might be possible . Environmental factors can also affect human skills . such as playing a musical instrument . For example , cal traits such as muscle coordination and a good sense of FIGURE . I ' Heredity and caring will a play well But the musician when a peso plays a Violin , also needs instruction on how to play the instrument . genetically determined traits such Musical instruction is an environmental factor . as muscle coordination interact with environmental factors Such How can environmental factors affect ) a person height ?

as time spent in practice . Reading 59050 Assessment , Target Reading Skill identify Main Ideas Relating Cause and Effect Explain how Read the text following the heading Girl or green is inherited . Why is the Boy ( page 195 ) Identify the main idea and condition more common in males than in two supporting details . females ?

a . Reviewing Are a person characteristics Reviewing Key concepts determined only by genes ?

Explain . of . Applying Concepts Explain what factors ' a humans ( might work together to enable a great soccer of a trait that follows each pattern . player kick a ha long distance Summarizing How many human blood types are there ?

Summarize how blood . Writing in Science Drawing Conclusions has blood type . Can either of his parents have Think of an blood type AB ?

Explain your answer . ability you admire . such as painting . dancing , a . Reviewing What are the functions of . OI playing games skillfully . the sex ?

Write I paragraph how genes and . Comparing and Contrasting Contrast ' 33 the sex chromosomes found in human enable I person to develop this ability . females and human males . 198 Human Genetic Disorders I aroma a in Students know plant and HOW Many ?

animal cells contain many The photo at shows the sands of different genes and cally have two copies of every gene . from a Ce of If the two copies ( or alleles ) of the th gene may or may not be genetic disorder , The chromosomes and one may be dominant in have been sorted into pairs . mining the phenotype while the . Count the number of other IS recessive . chromosomes in the photo . what We two major causes of . How does the number of genetic disorders in humans ?

How do geneticists trace the umber inheritance of traits ?

13 ( em ?

How are genetic disorders Think It Over diagnosed and treated ?

Inferring How do you think a cell could have ended up with this number of chromosomes ?

Key Terms ( Hint Think about the events that occur during meiosis . genetic disorder pedigree ' The air inside the stadium was hot and still . The crowd cheered loudly as the runners approached the starting blocks . At the crack of the gun , the runners sprinted down the track . Seconds later , the race was over . The runners , bursting with pride , hugged each other and their coaches . athletes were running in the Special Olympics , a competition for people with disabilities . Many of the athletes who compete in the Special Olympics have disabilities that result from genetic disorders . disorder is an abnormal condition that a person inherits through genes or chromosomes . Runners in the Special Olympics 199

FIGURE Disease Normally , red blood cells are shaped like round disks ( top ) In a person with disease , red blood cells can become shaped ( bottom ) Skills Activity Predicting A man has disease . His wife does not have the disease , but is heterozygous for the trait . Predict the probability that their child will have disease . Hint Construct a square . 2006 Causes of Genetic Disorders Recall that a person normally inherits two copies of a gene , one from each parent . But sometimes a person inherits an mal version of a gene that can lead to a disorder . It is not rate to say that someone has a gene for a disorder . Instead , a person has an allele for the trait . Some genetic disorders are caused by changes in the DNA of genes . Other disorders are caused by changes in the overall structure or number of chromosomes . Common genetic disorders include cystic . disease , hemophilia , and Down syndrome . Cystic Fibrosis Cystic is a disorder in which the body produces abnormally thick mucus in the lungs and intestines . The thick mucus the lungs , making it hard for the affected person to breathe . Cystic fibrosis is caused by a recessive allele on one chromosome . The allele is the result of a mutation in which three bases are removed from a DNA molecule . Disease disease hemoglobin , a protein in red blood cells that carries oxygen . When oxygen concentrations are low , the red blood cells of people with the disease have an unusual sickle shape . red blood cells clog blood vessels and can not carry as much oxygen as normal cells . The allele for the trait is with the normal allele . A person with two alleles will have the disease . A person with one allele will duce both normal hemoglobin and abnormal hemoglobin . This person usually will not have symptoms of the disease . Hemophilia Hemophilia is a disorder in which a persons blood clots very slowly or not at all . People with the disorder do not produce one of the proteins needed for normal blood clotting . The danger of internal bleeding from small bumps and bruises is very high . Hemophilia is caused by a sive allele on the chromosome . Down Syndrome In Down syndrome . a person cells have an extra copy of chromosome 21 . In other words , instead of a pair of chromosomes , a person with Down syndrome has three of that chromosome . Down syndrome most often occurs when chromosomes fail to separate properly during meiosis . People with Down syndrome have some degree of mental retardation . How is the DNA in the allele different loading Chick fromthe normal allele ?

Pedigrees lmagine that you are a geneticist who is interested in tracing the occurrence of a genetic disorder through several tions of a family . What would you do ?

One important tool isa pedigree . A pedigree is a chart or family tree that tracks which members of a family have a particular trait . The trait in a pedigree can be an ordinary trait , such as a widow peak , or a genetic disorder , such as cystic fibrosis . Figure 10 shows a pedigree for albinism , a condition in which if a person skin . hair , and eyes lack normal coloring . Go more 10 ' The father in the photograph has albinism . The pedigree For Pedigree activity shows the inheritance of the allele for albinism in three ! generations of a family . Interpreting Diagrams Where Web Code is an albino male shown in the pedigree ?

A circle represents a female . A square represents a male . i A horizontal line connecting a male and a A vertical line and a bracket . female represents a marriage . connect the parents to their children . A completely shaded square or circle indicates that the person has the trait . A circle or square that is not shaded ' indicates thata ' i person neither has person ' ta er the trait nor is a carrier .

FIGURE 11 Living With Hemophilia with proper care , people with hemophilia can manage their disorder . Interpreting Diagrams In the pedigree , how many people have hemophilia ?

I Male with hemophilia A Hemophilia Pedigree A The pedigree shows the Inheritance of hemophilia , a disorder . in a family . Notice that some females are carriers , and some males have the disorder . Managing Genetic Disorders Years ago . doctors had only squares and pedigrees to help them predict whether a child might have a genetic disorder . doctors use tools such as to help diagnose genetic disorders . People with genetic disorders are helped through medical care . education , job training , and other methods . To detect chromosomal disorders such as Down syndrome , a doctor examines the chromosomes from a son cells . The doctor uses a karyotype to examine the . A ( KA rec uh ) is a picture of all the chromosomes in a cell . The chromosomes in a karyotype are arranged in pairs . A karyotype can reveal whether a person has the correct number of chromosomes in his or her cells . The Standards activity on page 199 shows a karyotype from a girl with Down syndrome . Genetic Counseling A couple that has a family history of a genetic disorder may turn to a genetic counselor for advice . Genetic counselors help couples understand their chances of having a child with a particular genetic disorder . Genetic counselors use tools such as , pedigree charts , and squares to help them in their ) What do genetic counselors do ?

202 Physical Therapy Trained medical workers help hemophilia patients cope with their disorder . Here , a boy receives physical therapy . Sports A boy with hemophilia learns how to play golf . The disorder does not stop people from living active lives . Dealing with Genetic Disorders People with genetic orders face serious challenges , but help is available . Modifying an affected persons example , through , diet , or help manage some disorders . People with disease take folic acid . a vitamin , to help their bodies make red blood cells . Through education and job training , adults with Down syndrome can work in many places . Fortunately , most genetic disorders do not prevent ple from living active . productive lives . A Reading . Vocabulary Skill Academic Words Applying Concepts Sam has hemophilia . Use the words effect and normal to explain the Sam brother . mother . and father do not have between hemophilia and . hemophilia . Draw a pedigree showing who Reviewing Key concepts has the disorder and who is a carrier . a . Reviewing What is a type ?

Identifying Identify the two maior causes Inferring would a reveal the presence of genetic disorders in humans . of disease ?

Why Why not ?

Explaining Which of those two causes is responsible for Down syndrome ?

Describing How are the cells of a person with Down syndrome different from those of a person without the disorder ?

a . Defining What is a pedigree ?

Inferring Why are pedigrees helpful in understanding genetic disorders ?

Chapter 203 Family Puzzle Problem A husband and wife want to understand the probability that their children might inherit cystic fibrosis . How can you use the information in the box labeled Case Study to predict the probability ?

Skills Focus interpreting data , predicting Materials 12 index cards scissors marker Procedure . Read the Case Study . in your notebook , draw a pedigree that shows all the family bers . Use circles to represent the females , and squares to represent the males . Shade in the circles or squares representing the who have cystic fibrosis . You know that cystic fibrosis is controlled by a recessive allele . To help you figure out Joshua and Bella family pattern , create a set of cards to represent the alleles . Cut each of six index cards into four smaller cards . On 12 of the small cards , write to represent the dominant normal allele . On the other 12 small cards , write forthe recessive allele . Case Study Joshua and Bella Joshua and Bella have a son named A i . Ian has been diagnosed with ' I 77 ' Joshua and Bella are both healthy . I Bella parents are both healthy . Joshua are both healthy . Joshua . has cystic . ir i so . Begin by using the cards to represent alleles . Since he has cystic fibrosis , what alleles must he have ?

Write in this genotype next to the pedigree symbol for Ian . Joshua sister , Sara , also has cystic fibrosis . what alleles does she have ?

Write in this genotype next to the pedigree symbol that represents Sara . Now use the cards to figure out what types Joshua and Bella must have . Write their next to their symbols in the pedigree . Work with the cards to figure out the types of all other family members . Fill in each person genotype next to his or her symbol in the pedigree . if more than one genotype is possible , write in both . Analyze and Conclude interpreting Data What were the possible of Joshua parents ?

What were the of Bella parents ?

Predicting Joshua also has a brother . What is the probability that he has cystic fibrosis ?

Explain . Communicating imagine that you are a genetic counselor . A couple asks why you need information about many generations of their families to draw conclusions about a hereditary condition . Write an explanation you can give to them . More to Explore Review the pedigree that you just studied . What data suggest that the traits are not ?

Explain .

Section Tech Design Advances in Genetics A Standards Framework Mitochondria What Do Fingerprints Reveal ?

Label a sheet of paper with your name . Then roll one of your , in ssi . fingers to side on an ink pad . Make a fingerprint by to grandchildren with gram cap carefully rolling your inked finger on the paper . Divide into groups . Each group should choose one member to students know DNA ( deny . use the same finger to make a second fingerprint on a sheet ribonucleic acid ) is the genetic of paper . Leave the paper unlabeled . I ' Of living 55 . Exchange your group fingerprints with those from another he ' 95 ' group . Compare each labeled fingerprint with the fingerprint ea ' on the unlabeled paper . Decide whose fingerprint it is . Ways of producing . Wash your hands after completing this activity . organisms with desired traits ?

Think it over what are two of Inferring Why are fingerprints used to identify people ?

Would DNA in human it be useful if DNA Could be used to identify organisms ?

genetics ?

Key Terms , breeding Would you like to have your picture taken with a . ed , member ?

Adrian , a teacher in the village hybridization of Cheddar in . has actually done that . All that left of clone his ancient relative , known as Cheddar Man , is a skeleton . The 99 ?

skeleton was discovered in a cave near the village . DNA analysis . Ef indicates that and Cheddar Man are relatives . Like your , your DNA is different from everyone else . Because of advances in genetics , DNA evidence can show many things , such as . family relationships . I FIGURE 12 Distant Relatives Adrian visits his distant relative , Cheddar Man . Unfortunately , Cheddar Man can not respond to questions about life years ago .

mums Selective Breeding Inbreeding Turkeys such asthe one Genetic techniques have enabled people to produce with white feathers were isms with desirable traits . Selective breeding , cloning , i ! and genetic engineering are three methods for developing wild turkeys organisms with desirable traits . The process of selecting organisms with desired traits to be parents of the next generation is called selective breeding . Thousands of years ago , in what is now Mexico , the food that we call corn was developed in this way . Every year , farmers saved seeds from the healthiest plants that produced the best food . In the spring , they planted those seeds . By repeating this process over and over , farmers developed plants that better corn . People have used selective breeding with many different plants and animals . Two selective breeding techniques are inbreeding and hybridization . Inbreeding The technique of inbreeding involves crossing two individuals that have similar characteristics . For example . suppose a male and a female turkey are both plump and grow quickly . Their offspring will probably also have those desirable qualities . Inbred organisms have alleles that are very similar to those of their parents . inbred organisms are genetically very similar . Therefore , inbreeding increases the probability that organisms may inherit alleles that lead to genetic disorders . For example , inherited hip problems are common in many breeds of dogs . Hybridization in hybridization ( brid ih shun ) breeders cross two genetically different individuals . The hybrid organism that results is bred to have the best traits from both parents . For example , a farmer might cross corn that produces many kernels with corn that is resistant to disease . The result might be a hybrid plant with both of the desired traits . i What is the goal of hybridization ?

FIGURE 14 Hybridization and Red Delicious Wefe 10 Red Delicious Empire produce Empire apples . Applying Concepts What desirable traits might breeders have been trying to produce ?

Math Statistics . Data Analysis . and Probability Worldwide Rice Production ' Data Changing Rice Production The graph shows how worldwide rice production changed between 1965 and 2000 . New , hybrid varieties of rice plants are one factor that has affected the amount of rice produced . Reading Graphs According to the graph , how did rice production change between 1965 and 2000 ?

Reading Graphs How many metric tons of rice per hectare were produced in How many were produced in 2000 ?

Calculating Calculate the difference between rice production in 1965 and 2000 . Rico Production ( metric tons per hectare ) Developing Hypotheses What factors besides new varieties of plants might help account for the difference in rice production between 1965 and 2000 ?

Cloning For some organisms , a technique called cloning can be used to produce offspring with desired traits . A done is an organism that has exactly the same genes as the organism from which it was produced . It is hard to clone some kinds of plants , such as an African violet . lust cut a stem from one plant , and put the stem in soil . Water it , and soon you will have a whole new plant . The new plant is genetically identical to the plant from which the stem was cut . Researchers have also cloned animals such as sheep and pigs . The methods for cloning these animals are complex . They involve taking the nucleus of an animal body cell and using that nucleus to duce a new animal . How can a clone of a plant . be produced ?

Cloned Goats These goats were produced by cloning .

Genetic Engineering Geneticists have developed mother powerful technique for producing organisms with desired traits . In this process . called genetic genes from one organism are transferred into the DNA of another organism . Genetic engineering can produce medicines and improve food crops . Genetic Engineering in Bacteria One type of FIGURE 15 engineered bacteria produces a protein called Injections Genetic Engineering of insulin are needed by many people with diabetes . Bacteria Scientists use genetic engineering have a single DNA molecule in the cytoplasm . Some bacterial ma ' cells also contain small circular pieces of DNA called plasmids . produce important human , sud as insulin In Figure 16 , you can see how scientists insert the DNA for a , Haw doe , human gene into the plasmid of a bacterium . a human insulin gene become part of a plasmid ?

Scientists remove plasmids , small rings of DNA . from bacterial cells . I Insulin gene An enzyme cuts open the plasmid DNA . The same enzyme removes the human insulin gene from its chromosome . Human DNA The human insulin gene attaches to the open ends of the plasmid to form a closed ring . Some bacterial cells take up the plasmids that have the insulin gene . When the cells reproduce , the new cells will contain copies of the engineered plasmid . The foreign gene directs the cell to produce human insulin . 2080

Normal zebra danio A Genetically engineered zebra danio Once the gene is inserted into the plasmid , the bacterial cell and all its offspring will contain this human gene . As a result , the bacteria produce the protein that the human gene codes this case , insulin . Because bacteria reproduce quickly , large amounts of insulin can be produced in a short time . Genetic Engineering in Other Organisms Scientists can also use genetic engineering techniques to insert genes into mals . For Example , human genes can be inserted into the of cows . The cows then produce the human protein for which the gene codes in their milk . Scientists have used this technique to duce the blood clotting protein needed by people with hemophilia . Genes have also been inserted into the cells of plants , such as tomatoes and rice . Some of the genes enable the plants to survive in cold temperatures or in poor soil . Other genetically engineered crops can resist insect pests . Gene Therapy Someday it may be possible to use genetic engineering to correct some genetic disorders in humans . This process , called gene therapy , will involve inserting copies of a gene directly into a person cells . For example , doctors may be able to treat hemophilia by replacing the defective allele on the chromosome . The persons blood would then clot normally . Concerns About Genetic Engineering Some people are concerned about the effects of genetic engineering . For example , some people think that genetically engineered crops may not be entirely safe . People fear that these crops may harm the environment or cause health problems in humans . To address such concerns , scientists are trying to learn more about the effects of genetic engineering . Reading How do genetic engineering techniques enable ) scientists to produce clotting proteins ?

FIGURE 17 Genetically Engineered Fish The bright red zebra are the result of genetic engineering . 45 ' INKS , For links on genetic engineering Web Code 209 18 The Human Genome Project Scientists on the Human Genome Project continue to study human DNA . Learning About Human Genetics of DNA technology include studying the human genome in detail and identifying people . The Human Genome Project A genome is all the DNA in one cell of an organism . The main goal of a project called the Human Genome Project has been to identify the DNA sequence of every gene in the human genome . Scientists have learned that the DNA of humans has at least genes . The average gene has about bases . Scientists now know the DNA sequence of nearly every human gene . DNA Fingerprinting DNA technology can also identify people and show whether people are related . Nuclear DNA from a persons cells is broken down into small pieces , or ments . Selected fragments are used to produce a pattern called a DNA . Except for identical twins , no two people have exactly the same DNA . Scientists can also use mitochondrial DNA to determine a person identity . Mitochondria contain their own DNA , which is inherited from the mother through the egg cell . This means that a child has virtually the same mitochondrial DNA as his or her mother . By analyzing mitochondrial DNA , it is possible to trace inheritance from grandmothers to grandchildren with great certainty . For example , mitochondrial DNA was used to lish the relationship between Cheddar Man and his descendant . Framework . leading Vocabulary Skill Academic Words What is hybridization ?

Use the word technique in your answer . Reviewing Key Concepts a . Listing List three methods that scientists can use to develop organisms with desirable traits . Describing describe each method . Applying Concepts Which method would be the best way of producing a plant similar to the one you already have ?

Explain . At Home Activity Food and Selective Breeding Go to a grocery store with a family member . Discuss how fruits and vegetables have been produced by selective breeding . Choose a fruit or vegetable , and identify the traits that make it valuable . a . Reviewing What are two applications of DNA technology ?

Making Judgments Do you think DNA would be useful in solving crimes ?

Explain your reasoning . 210 Guilty or Innocent ?

Problem A crime scene may contain hair , skin , or blood from a criminal . These materials all contain DNA that can be used to make a DNA fingerprint . A DNA fingerprint , which consists of a series of bands , is something like a bar code . How can a DNA fingerprint identify individuals ?

Skills Focus drawing conclusions , inferring Materials bar codes hand lens Procedure Analyze and conclude . Look at the photograph of DNA band . Drawing Conclusions Based on your terns shown at right . Each person DNA ings , were any of the suspects present at the produces a unique pattern of these bands . crime scene ?

Support your conclusion with . Now look at the Universal Product Code , also ' called a bar code , shown below the DNA . Inferring Why do people DNA patterns bands . A bar code can be used as a model of differ so greatly ?

DNA band the bar . Drawing Conclusions How would your with the DNA wha they have in be affected if you learned that the ' suspect whose DNA matched the evidence . Suppose that a burglary has taken place , and had an identical twin ?

he ' the ' Communicating Suppose you are a defense tron . Your teacher will give you a bar code . DNA evidence that the that ' DNA bloodstain at the scene of a crime belongs to he a ha DNA your client . Do you think this DNA evidence ' a ' should be enough to convict your client ?

sentence describing what you will look for as write speech you might give to me in you try to match each suspect DNA to the of you , DNA sample from the crime scene . You will now be given bar codes More to DNA take the suspects Do the DNA fin of a ha with the bar would show ?

that represents DNA from the crime scene . your thinking . Use your comparisons to determine whether any of the suspects was present at the crime scene . Chapter 111 Technology and Society DNA Fingerprinting What do you have that no one else has ?

Unless you are an identical twin , your DNA is unique . Because one person DNA is like no one else , it can be used to produce genetic can tie a person to the scene of a crime . They can prevent the wrong person from going to jail . They can also be used to identify skeletal remains . Today , soldiers and sailors , give blood and saliva samples so their DNA can be saved . Like the past , tags tags that soldiers wear , DNA records can be used to ?

main methods for identifying identify the bodies of unknown soldiers or . Skew , remains i , I ' This enzyme cuts the DNA . After a sample of DNA is ' extracted from the body , an enzyme cuts the DNA strand into several smaller pieces . The DNA fragments are loaded into a gel that uses electric current to separate fragments . Larger fragments of DNA move through the gel more slowly than the smaller fragments . 212

iv Analyzing DNA In one method of DNA analysis , DNA from saliva , blood , bones teeth , or other or tissues is taken from cells . Special enzymes are added to cut the DNA into small pieces . Selected pieces are put into a machine that runs an electric Current through the DNA and sorts the pieces by size . The DNA then gets stained and photographed . When developed , a unique banded pattern . similar to a product bar code , is revealed . The pattern can be compared to other samples of DNA to determine a match . Limitations of DNA Fingerprinting Like all technology , DNA has its limitations . DNA is very fragile and the produced can be difficult to read if the DNA samples are old . In rare instances , DNA from the people testing the samples can become mixed in with the test samples and produce inaccurate results . DNA testing is also time consuming and expensive . Once the DNA fragments have separated , the gel is stained . The unique banded pattern is a DNA . identify the Need Make a list of at least situations in which DNA could be useful . Research Research the situations you listed in Question to find out if DNA analysis is or can be used in each . Write Choose one application of DNA analysis and write one or two paragraphs to explain when the application can be used . For More on DNA Visit Web Code Chapters 213

Chapter Study Guide , A person traits depend on which alleles are inherited front each ?

I Idea parent . how those alleles work together , and environmental factors . ti Human Inheritance ( Key Concepts . Some human traits are controlled by single genes with two alleles . and others by single genes with multiple alleles . Still other traits are controlled by many genes that act together . The sex chromosomes carry genes that determine whether a person is male or female . They also carry genes that determine other traits . Many of an organism characteristics are determined by an interaction between genes and the environment . Key Terms multiple alleles sex chromosomes gene carrier if Human Genetic Disorders ( Key Concepts Some genetic disorders are caused by mutations in the DNA of genes . Other disorders are caused by changes in the overall structure 01 ' number of chromosomes . One important tool that geneticists use to trace the inheritance of traits in humans is pedigree . Today doctors use tools such as to help detect genetic disorders . People with genetic disorders are helped through medical care , education . job training . and other methods . Key Terms genetic disorder pedigree karyotype 214 Advances in Genetics ( Key Concepts Framework , Selective breeding , cloning , and genetic engineering are three methods for developing organisms with desirable traits . of DNA technology include studying the human genome in detail and identifying people . Key Terms selective breeding inbreeding , hybridization done genetic engineering gene therapy genome

Fon Visit Web Code A Target Reading Skill ' Identifying Main Ideas Reread the ' three paragraphs following the heading The Effect of Environment , page . a graphic organizer like the one at new am right , identify the main idea and supply Ii . the second detail . 81 Reviewing Key Terms Choose the letter of the best answer . Complete the following sentences so that your ' A gem , that is carried on the , answers clearly explain the Key Terms . In humans . the and chromosomes are Came sex chromosomes , which determine the ed gene . A person that has an extra copy of ' one chromosome 21 is an example of someone A . An abnormal condition that a person inherits with a genetic disorder because . genes or Chromosomes ' called . Selecting and growing only the healthiest corn ' plants every season is an example of selective . I . multiple allele . Process genetic . that are simi se . Which of the following would most likely be . used to diagnose Down syndrome ?

10 ' karyotype is an example of genetic engineering , a pedigree a test a square a human gene into a bacterial Ce A plasmid is an example of ' i ' he ! urea i ' I lab . Man I . DNA fingerprinting . mas gang , genetic engineering . on . An organism that has the same genes as the . from which it was produced is clone . hybrid . genome . pedigree . Chapters 215

Review and Assessment Checking Concepts 11 . Explain why there are a wide variety of for skin color in humans . 12 . Traits controlled by recessive alleles on the chromosome are more common in males than in females . Explain why . 13 . What is disease ?

How is this disorder inherited ?

14 . What is a pedigree ?

How do geneticists use pedigrees ?

15 . Describe two ways in which people with genetic disorders can be helped . 16 . Explain how a horse breeder might use selective breeding to produce horses that have golden coats . 17 . Describe how gene therapy might be used in the future to treat a person with hemophilia . 18 . What is the Human Genome Project ?

Thinking Critically 19 . Problem Solving A woman with normal color vision has a colorblind daughter . What are the and of both parents ?

20 . Calculating If a mother is a carrier of hemophilia and the father does not have hemophilia , what is the probability that their son will have the trait ?

Explain your answer . 21 . Interpreting Diagrams The allele for cystic is recessive . Identify which members of the family in the pedigree have cystic and which are carriers . Mother Father Joe Sarah Emily 216 Applying Skills Use the square to answer Questions . The square below shows how muscular dystrophy , a recessive disorder , is inherited . Father ( normal ) Mother ( carrier ) 22 . Interpreting Data What is the probability that a daughter of these parents will have muscular dystrophy ?

Explain your answer . 23 . Interpreting Data What is the probability that a son of these parents will have muscular dystrophy ?

Explain your answer . 24 . Inferring it possible for a woman to have muscular dystrophy ?

Why or why not ?

Standards Investigation Performance Assessment Present your display board to your class . Highlight important facts about the genetic trait you selected . Discuss the innovative designs you incorporated into the display board In your presentation , highlight the interactive part of your investigation .

09 ' Choose the letter of the best answer . To produce a human protein through genetic engineering , scientists use A a bacterial gene inserted into a human chromosome . a human gene inserted into a plasmid . a bacterial gene inserted into a plasmid . a human gene inserted into a human chromosome . Down syndrome is an example of a genetic disorder in which A one DNA base has been added . one DNA base has been deleted . one chromosome is substituted for another . an extra chromosome is added to a pair . The square shows the probability that the children of this couple will inherit hemophilia . Which of the following statements best describes the pattern of inheritance in this family ?

A All the sons will have hemophilia . All the daughters will have hemophilia . 50 of daughters and 50 of sons will have hemophilia . 25 of all children will have hemophilia . Height in humans is an example of a trait that is controlled by A a single gene with two alleles . a single gene with multiple alleles . many genes . environmental factors only . Practice Success it ?

Tracker at Use the pedigree to answer Questions . First generation Second generation Third generation Key I . I Person with disease I Carrier of ell disease . How many people in the second generation have disease ?

A none one person two people three people . Which statement is true about the third generation in the pedigree ?

A No one has disease . Everyone has disease . Everyone has at least one allele for disease . No one has any alleles for disease . ldea identical twin boys were separated at birth and raised by different families . One boy is tall and is an outstanding soccer player . The other boy is shorter and not very athletic , but he is a good musician . Which of the boys characteristics were by genetics ?

Which were by environment ?

Chapter 217