Part A: The Inheritance Pattern of FH - San Dieguito Union …teachers.sduhsd.net/ahaas/Biology/Genetics and Meiosi… · · 2010-04-19When Mendel crossed true-breeding pea plants

UNIT 4 CHAPTER 10 Mendel and Meiosis 7

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Tracking a High-CholesterolGene

Chapter

10Chapter Real World BioApplicationsReal World BioApplications

Familial hypercholesterolemia, or FH, is apotentially lethal, inherited disorder character-

ized by an extremely high blood cholesterol level—500 milligrams per deciliter or more compared tothe under 200 milligrams per deciliter that physi-cians prefer to see. People with high cholesterol areunusually prone to atherosclerosis, the condition inwhich cholesterol and other substances build up on

artery walls, eventually blocking the artery andoften causing a heart attack or stroke. By some esti-mates, FH affects about a half million people in theUnited States, and each has a 50–50 chance of pass-ing the disorder on to offspring. In this activity,you’ll analyze the inheritance pattern of FH andlearn how scientists track the family history of FHto save lives.

Part A: The Inheritance Pattern of FH

1. Scientists have discovered that the cause of FH is a defect in cells that prevents them from extractingLDLs (low-density lipoproteins, the so-called bad cholesterol) from the bloodstream. As a result, cir-culating cholesterol particles are free to accumulate within blood vessels. Individuals homozygous forthe defective allele, L′L′, have sixtimes the normal cholesterol level.When they mate with individualshaving normal cholesterol levels, LL,the F1 offspring are heterozygous,LL′, showing an intermediate condi-tion of twice the normal blood cho-lesterol level (Figure 1). What patternof inheritance does this illustrate?

2. What are the expected genotypic andphenotypic ratios of F2 offspring froma mating between heterozygous indi-viduals? Use the Punnett square tofind your answer.

3. What phenotypic and genotypic ratios could you expect from a mating between a heterozygous indi-vidual and a normal homozygous individual (a.)? Between a heterozygous individual and an individualhomozygous for the defective allele (b.)? Use the Punnett squares to find your answers.a. b.

L′L′Very high

cholesterol

LL′High

cholesterol

L′

L′

L L

LL′

LL′ LL′

LL′

All high cholesterol

LLNormal

cholesterol

Figure 1

Genotypic ratio ________________

Phenotypic ratio ________________

Genotypic ratio

________________

Phenotypic ratio

________________

Genotypic ratio

________________

Phenotypic ratio

________________

8 CHAPTER 10 Mendel and Meiosis UNIT 4

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Part B: Tracking the Family History of FHBecause individuals with familial hypercholesterolemia have a 50 percent chance of passing thedisorder on to offspring, scientists have recently launched an extensive campaign to track downand alert relatives of people with FH. To show the transmission of a trait through several gener-ations of a family, scientists construct a pedigree of the family. Study the key and the pedigreediagram in Figure 2 to learn the symbols.

1. What are the benefits of being able to see the transmission of a trait over the history of a family?

2. Refer to the pedigree diagram in Figure 2. What is the probability of individuals II-3 and II-4 havinga child with very high cholesterol?

3. Refer to the pedigree diagram in Figure 3. List the genotype of each individual marked with a number.

4. In the pedigree in Figure 3, if individuals II-6and II-7 have another child, what is the chancethat he or she will have very high cholesterol?Complete the Punnett square to support youranswer.

I

II

III

1 2

1 2 3

1

3 4

4 5 6 7

2 3 4

� Female with normal cholesterol

� Female with high cholesterol

� Female with very high cholesterol

� Male with normal cholesterol

� Male with high cholesterol

� Male with very high cholesterol

Key I

II

III

1 2

1

1 2 3 4

2 43

ChapterTracking a High-Cholesterol Gene

Chapter

10 Real World BioApplicationsReal World BioApplications

Figure 2

Figure 3


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In your textbook, read why Mendel succeeded.

Complete each statement.

1. Mendel was the first person to succeed in predicting how traits are ___________________________

from generation to generation.

2. Mendel used ___________________________ plants in his experiments.

3. In peas, both male and female sex cells—___________________________—are in the same flower.

4. ___________________________ occurs when the male gamete fuses with the female gamete.

5. Mendel used the process called ___________________________ when he wanted to breed one plant

with another.

6. Mendel carefully ___________________________ his experiments and the peas he used.

7. Mendel studied only one ___________________________ at a time and analyzed his data

mathematically.

In your textbook, read about Mendel’s monohybrid crosses.

Refer to the table of pea-plant traits on the right. Then complete the table on the left by filling inthe missing information for each cross. The first one is done for you.

Mendel and MeiosisChapter

10Chapter

Section 10.1 Mendel’s Laws of Heredity

Reinforcement and Study GuideReinforcement and Study Guide

F1 generation

Parent Plants Offspring Appearance

8. round � wrinkled Rr roundRR � rr

9. yellow � green a. b.YY � yy

10. axial � terminal Aa a.AA � ______

11. tall � short Tt a.______ � ______

12. inflated � constricted a. b.______ � ii

Pea-Plant Traits

Trait Dominant Recessive

seed round wrinkledshape (R) (r)

seed yellow greencolor (Y) (y)

flower axial terminalposition (A) (a)

plant tall shortheight (T) (t)

pod inflated constrictedshape (I) (i)


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ChapterMendel and Meiosis, continued

Chapter

10Reinforcement and Study GuideReinforcement and Study Guide

Section 10.1 Mendel’s Laws of Heredity

In your textbook, read about phenotypes and genotypes and Mendel’s dihybrid crosses.

If the statement is true, write true. If it is not, rewrite the underlined part to make it true.

13. A pea plant with the genotype TT has the same phenotype as a pea plant with genotype tt. _________

14. When Mendel crossed true-breeding pea plants that had round yellow seeds with true-breeding pea

plants that had wrinkled green seeds, some of the offspring had round yellow seeds because round

and yellow were the dominant forms of the traits. ___________________________________________

15. When Mendel allowed heterozygous F1 plants that had round yellow seed to self-pollinate, he found

that some of the F2 plants had wrinkled green seeds. _________________________________________

16. The law of independent assortment states that genes for different traits are inherited independently

of each other. _________________________________________________________________________

In your textbook, read about Punnett squares and probability.

The Punnett square below is for a dihybrid cross between pea plants that are heterozygous forseed shape (Rr) and seed color (Yy). Complete the Punnett square by recording the expectedgenotypes of the offspring. Then answer the questions.

17. Use the chart on the previous page to determine the phenotypes of the offspring. Record the pheno-

types below the genotypes in the Punnett square. Is an offspring produced by the cross more likely to

have wrinkled seeds or round seeds? _______________________________________________________

18. What is the probability that an offspring will have wrinkled yellow seeds? _______________________

RY Ry rY ry

RY

Ry

rY

ry


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Master

16Master

Dihybrid Cross Use with Chapter 10, Section 10.1

Reteaching SkillsReteaching Skills

TR Tr tR tr

TR

Tr

tR

tr

TtRrTall;

roundseeds

TtRrTall;

roundseeds

TTRR

Tall;roundseeds

TTRrTall;

roundseeds

TtRRTall;

roundseeds

TtRrTall;

roundseeds

TTRrTall;

roundseeds

TTrrTall;

wrinkledseeds

TtRrTall;

roundseeds

TtrrTall;

wrinkledseeds

TtRRTall;

roundseeds

TtRrTall;

roundseeds

ttRRShort;roundseeds

ttRrShort;roundseeds

TtRrTall;

roundseeds

TtrrTall;

wrinkledseeds

ttRrShort;roundseeds

ttrrShort;

wrinkledseeds

TTRRTall; round

seeds

ttrrShort;wrinkled seeds

Gametes

Gam

etes

F1 (Male)

F 1 (F

emal

e)

F2 Generation

Parent

Pare

nt

P1


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Worksheet

16Worksheet

Dihybrid CrossReteaching SkillsReteaching Skills

Use with Chapter 10, Section 10.1

1. Describe the P1 dihybrid cross shown in the transparency.

2. Describe the F1 dihybrid cross shown in the transparency.

3. Identify the combinations of alleles that are contained in the gametes of the F1 plants.

4. Complete the Punnett square for the F2 generation. Each box should contain four alleles, two for each gene. One allele for each gene came from the female parent. Theother allele for each gene came from the male parent. Each box should also identify thephenotype of each offspring. How many different genotypes are there in your completedsquare? Identify them.

5. What are the proportions of the different genotypes of the F2 generation?

6. What are the phenotypic proportions?

7. In studying the dihybrid crosses, Mendel found that the inheritance of one trait does notinfluence the inheritance of another trait. What would be another way of expressing thisfact, using the phenotypes of the F2 generation on the transparency?


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Mendel and MeiosisChapter

10Chapter Problem SolvingProblem Solving


1. The allele for tall pea plants (T) is dominant to the allele for short plants (t). What are the genotypes of theparents?

2. Fill in the blanks on the diagram with the genotypes of the parents and each of the F1, F2, and F3 plants.The F1 plant and each of the F2 plants were self-pollinated. If necessary, use Punnett squares to help youdetermine the genotypes of the F2 and F3 plants.

3. Why is only one phenotype given for the offspring of one of the tall F2 plants and one of the short F2 plants?

4. The allele for green pea pods (G) is dominant to the allele for yellow pods (g). Suppose a heterozygous tallparent plant is heterozygous for green pods. Draw a Punnett square that shows all the possible genotypesfor the F1 generation that would result from self-pollination of the parent plant.

5. Expressed as a percentage, what is the probability that a seed produced by the P1 plant will produce a tallplant with green pods? A tall plant with yellow pods? A short plant with green pods? A short plant withyellow pods?

The phenotypes of three generations of peaplants produced by crossing a tall plant with

a short one are shown below. Use the diagram toanswer the questions that follow.

Tracing a Family Tree and Calculating Probabilities

tall

tall

tall

short×

tall tall tall short

tall

F1

P1

F2

F3 short

shorttall

tall tall tall short

tall


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Predicting CombinationsMaster

24Master Section FocusSection Focus


1 What possible combinations can result from combining one coin fromeach group?

2 What is the ratio of the possible combinations?

Group 1

Group 2


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Chromosome NumbersMaster

25Master


Section FocusSection Focus

1 What is the number of chromosomes in each body cell ofthese fruit flies?

2 How many chromosomes must each body cell of normaloffspring have?

Female fruit fly

Male fruit fly


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Master

14Master

Monohybrid Cross Use with Chapter 10, Section 10.1

Basic ConceptsBasic Concepts

P1

F1

F2

Tall pea plant Short pea plant

All tall pea plants

3 tall:1 short


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Worksheet

14Worksheet

Monohybrid CrossBasic ConceptsBasic Concepts


1. Describe a monohybrid cross of plants.

2. Compare the appearance of the plants in the F1 generation with those in the F2 generation.

3. What did Mendel call the observed trait and the trait that seemed to disappear in the F1 generation?

4. Describe the phenotype and genotype of the F1 generation plants.

5. What are the genotypes of the short plants in the P1 and F2 generations?

6. Why does the trait for shortness seem to skip a generation?

7. How did Mendel explain the reappearance of shortness in the F2 generation?


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ChapterMendel and Meiosis, continued

Chapter

10Chapter AssessmentChapter Assessment

Understanding Main Ideas (Part A)

In the space at the left, write the letter of the word or phrase that best completes the statement oranswers the question.

____________ 1. A white mouse whose parents are both white produces only brown offspring whenmated with a brown mouse. The white mouse is most probablya. homozygous recessive. b. heterozygous.c. homozygous dominant. d. haploid.

____________ 2. Polyploid organisms result froma. crossing over. b. nondisjunction. c. mitosis. d. random assortment.

____________ 3. The numbers in the diagram below represent the number of chromosomes found ineach of the dog cells shown.

The processes that are occurring at A and B area. mitosis and fertilization. b. meiosis and fertilization.c. mitosis and pollination. d. meiosis and pollination.

____________ 4. If a female guinea pig homozygous dominant for black fur color is mated with amale that is homozygous recessive for white fur color, in a litter of eight offspring,you would expecta. 8 black guinea pigs.b. 4 black and 4 white guinea pigs.c. 2 black, 4 gray, and 2 white guinea pigs.d. 8 white guinea pigs.

____________ 5. A dog’s phenotype can be determined bya. looking at the dog’s parents.b. examining the dog’s chromosomes.c. mating the dog and examining its offspring.d. looking at the dog.

____________ 6. A couple has two children, both of whom are boys. What is the chance that the parents’ next child will be a boy?a. 0% b. 50% c. 25% d. 75%

A

78

78

39

3939 78

39

B


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Chapter

Understanding Main Ideas (Part B)

In the space at the left, write the letter of the word or phrase that best completes the statement oranswers the question.

____________ 1. The diagram below shows a diploid cell with two homologous pairs of chromosomes.

Due to independent assortment, the possible allelic combinations that could be foundin gametes produced by the meiotic division of this cell area. Bb, Dd, BB, and DD. b. BD, bD, Bd, and bd.c. BbDd and BDbd. d. Bd and bD only.

____________ 2. When Mendel allowed tall heterozygous plants to self-pollinate, some of their off-spring were short because the alleles of the tall plantsa. were dominant. b. segregated during meiosis.c. were homozygous. d. crossed over during meiosis.

____________ 3. Which process would result in the formation of chromosome C from homologouschromosomes A and B?

a. asexual reproduction b. independent assortmentc. crossing over d. segregation

____________ 4. In chickens, rose comb (R) is dominant to single comb (r). A homozygous rose-combed rooster is mated with a single-combed hen. All of the chicks in the F1generation were kept together as a group for several years. They were only allowedto mate within their own group. What is the expected phenotype of the F2 chicks?a. 100% rose comb b. 75% rose comb and 25% single combc. 100% single comb d. 50% rose comb and 50% single comb

Mendel and Meiosis, continuedChapter


B b

d D

a = terminal flowers

I = inflated pod

C

I = inflated pod

A

a = terminal flowers

i = constricted pod

B

A = axial flowers


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Chapter

Thinking Critically

1. Approximately one out of every 20 Caucasian Americans has a recessive allele for a hereditary disor-der known as cystic fibrosis (CF), but only one out of every 2000 Caucasian babies born in the UnitedStates is afflicted with the disorder. These individuals have two alleles for CF. They produce largeamounts of mucus that accumulate in the lungs, liver, and pancreas. The mucus clogs important ductsin these organs and causes extensive damage. Why is there such a difference between the number ofindividuals who have the allele for CF and the number actually born with the disorder?

2. How can genetic recombination through segregation and crossing over during meiosis lead to variation in the offspring?

3. In guinea pigs, the allele for rough coat (R) is dominant to the allele for smooth coat (r), and the allelefor black fur (B) is dominant to the allele for white fur (b). If two guinea pigs that are heterozygous forrough, black fur (RrBb) are mated, what are the possible phenotypes and what is the frequency ofeach? Use a Punnett square to find the answers.




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Chapter

Thinking Critically

1. Approximately one out of every 20 Caucasian Americans has a recessive allele for a hereditary disor-der known as cystic fibrosis (CF), but only one out of every 2000 Caucasian babies born in the UnitedStates is afflicted with the disorder. These individuals have two alleles for CF. They produce largeamounts of mucus that accumulate in the lungs, liver, and pancreas. The mucus clogs important ductsin these organs and causes extensive damage. Why is there such a difference between the number ofindividuals who have the allele for CF and the number actually born with the disorder?

2. How can genetic recombination through segregation and crossing over during meiosis lead to variation in the offspring?

3. In guinea pigs, the allele for rough coat (R) is dominant to the allele for smooth coat (r), and the allelefor black fur (B) is dominant to the allele for white fur (b). If two guinea pigs that are heterozygous forrough, black fur (RrBb) are mated, what are the possible phenotypes and what is the frequency ofeach? Use a Punnett square to find the answers.




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Chapter

Applying Scientific MethodsSome biology students wanted to determine whether a pair of brown mice purchased at a pet store washomozygous dominant or heterozygous for fur color. They let the mice mate and examined the offspring.Six mice were born. All six had brown fur.

Some of the students felt that this was enough evidence to prove that the parent mice were homozygousfor brown fur color. Other students did not, so another experiment was planned.

1. Do you think the experiment described above was adequate to prove that the parent mice werehomozygous brown? Explain your answer, using the principles of genetics you have studied.

2. Describe the next experiment the students could conduct to determine whether the parent mice arehomozygous brown or heterozygous brown.




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Chapter

Applying Scientific Methods continued

3. What could you conclude if three of the offspring had white fur?

4. What could you conclude if all six of the offspring had white fur?



Documents

Part A: The Inheritance Pattern of FH - San Dieguito Union …teachers.sduhsd.net/ahaas/Biology/Genetics and Meiosi… · · 2010-04-19When Mendel crossed true-breeding pea plants