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Modern Biology Study Guide

SECTION 12-1 REVIEW

CHROMOSOMES AND INHERITANCE

VOCABULARY REVIEW Distinguish between the terms in each of the following pairs of terms.

1. sex chromosome, autosome

2. germ-cell mutation, somatic-cell mutation

3. translocation, nondisjunction

4. deletion, inversion

5. substitution, frameshift mutation

MULTIPLE CHOICE Write the correct letter in the blank.

1. Genes that belong to the same linkage group tend to be

a. located on different chromosomes.b. inherited together.

2. Two genes that are one map unit apart are separated by crossing-over

a. 1% of the time. b. 20% of the time. c. 50% of the time. d. 100% of the time.

3. Mutations that can be inherited arise in

a. somatic cells. b. body cells. c. germ cells. d. skin cells.

4. Which of the following sequences could result from an inversion of the sequence GAGACATT?

a. GAGCATT b. GTGACATT c. CTCTGATT d. GATACAGT

5. Which of the following is a point mutation that does not produce a frameshift?

a. substitution b. insertion c. deletion d. inversion

c. found only in males.d. found only in somatic cells.

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SHORT ANSWER Answer the questions in the space provided.

1. In humans and fruit flies, which parent determines the sex of the offspring? Explain why.

2. How did Morgan determine that red-eye color in Drosophila is an X-linked trait?

3. Explain why traits that are controlled by genes on the same chromosome do not always appear

in the expected ratio in offspring.

4. Critical Thinking Would a frameshift mutation have a more serious effect if it occurred near

the beginning of a gene or the end of a gene? Explain your answer.

STRUCTURES AND FUNCTIONS Use the data in the table below to indicate the positionof these genes on the chromosome map shown below. Assuming that the gene for whiteeyes has a chromosome map unit number of 1, write the map unit numbers above eachgene’s position on the chromosome map.

The Drosophila genes for whiteeyes, vermilion eyes, and minia-ture wings are located on the samechromosome. The table showshow often these genes are separated by crossing-over.

62 Section 12-1 Review

Name Class Date

Frequency of Genes crossing-over

Vermilion eyes and miniature wings 3%

White eyes and vermilion eyes 30%

White eyes and miniature wings 33%

0 40

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Modern Biology Study Guide

SECTION 12-2 REVIEW

HUMAN GENETICSVOCABULARY REVIEW Name a trait or genetic disorder that is caused by each of thefollowing patterns of inheritance.

1. polygenic inheritance

2. multiple alleles

3. autosomal dominant

4. sex-influenced trait

5. incomplete dominance

MULTIPLE CHOICE Write the correct letter in the blank.

1. Which individual(s) in the pedigree shown below must be a carrier?

a. 1 onlyb. 4 onlyc. 3 onlyd. both 1 and 4

2. Since the ABO blood group alleles are codominant, an individual with the genotype IAIB

will have blood type

a. A. b. B. c. AB. d. O.

3. Which of the following human traits is not a polygenic trait?

a. skin color b. eye color c. height d. ABO blood type

4. A trait whose expression is affected by the presence of sex hormones is said to be

a. sex-influenced. b. sex-linked. c. X-linked. d. Y-linked.

5. In humans, PKU can be treated by

a. insulin injections. c. gene therapy.b. diet. d. surgery.

Name Class Date

1 2

3 4

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SHORT ANSWER Answer the questions in the space provided.

1. Why is pattern baldness more common in men than in women?

2. Briefly describe how amniocentesis and chorionic villi sampling are used in genetic screening.

3. Explain the difference between a sex-linked trait and a sex-influenced trait.

4. Critical Thinking A couple has four children, and each child has a different ABO blood type.

What are the blood types and genotypes of the children and the parents?

STRUCTURES AND FUNCTIONS In the two pedigrees below, indicate all possible offspringin generation II by correctly filling in the male and female symbols for generation II. Use acompletely filled symbol to represent an individual who displays the trait and a half-filledsymbol to represent a carrier.

64 Section 12-2 Review

Name Class Date

Generation I

Generation II

X-linked recessive trait Autosomal recessive trait

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Modern Biology Study Guide Answer Key

Section 12-1 VOCABULARY REVIEW1. A sex chromosome contains genes that determine

an individual’s sex. An autosome is a chromosomethat is not directly involved in determining sex.

2. A germ-cell mutation occurs in one of an organism’sgametes; a somatic-cell mutation occurs in one ofthe other cells in an organism’s body.

3. Translocation occurs when a chromosome piecebreaks off and attaches to a nonhomologouschromosome; nondisjunction occurs when homo-logues fail to separate during meiosis, so that onegamete receives both homologues.

4. A deletion is a loss of a piece of chromosome dueto breakage. An inversion occurs when a brokenpiece of chromosome is reattached backwards.

5. In a substitution, one nucleotide in a codon isreplaced with a different one; in a frameshift mutation, the loss or addition of a nucleotidecauses the remaining codons to be incorrectlygrouped.

MULTIPLE CHOICE1. b 2. a 3. c 4. d 5. a

SHORT ANSWER1. The male parent determines the offspring’s sex.

Offspring that receive an X chromosome from themale parent will be female; those that receive a Y chromosome will be male.

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Modern Biology Study Guide Answer Key

2. Morgan crossed a white-eyed male with a femalehomozygous for red eyes, and then crossed mem-bers of the F1 generation resulting from the firstcross. He found that all of the white-eyed flies inthe F2 generation were male.

3. Crossing-over during meiosis causes homologouschromosomes to exchange alleles, resulting in newcombinations of alleles in the offspring.

4. A frameshift mutation would have a more seriouseffect if it occurred near the beginning of a gene,since it would change nearly all of the codons inthe gene. The resulting protein likely would benonfunctional.

STRUCTURES AND FUNCTIONSwhite eyes (map unit number 1), vermilion eyes (31),miniature wings (34)

Section 12-2 VOCABULARY REVIEW1. skin color, eye color, height, or hair color2. ABO blood groups3. Huntington’s disease4. pattern baldness5. wavy hair

MULTIPLE CHOICE1. d 2. c 3. d 4. a 5. b

SHORT ANSWER1. Pattern baldness is controlled by the allele B.

Testosterone interacts with the heterozygousgenotype (BB′) to produce baldness. Since maleshave higher levels of testosterone, BB′ males aremore likely to lose their hair than BB′ females.

2. A small sample is removed from the amniotic fluidsurrounding the fetus or from the chorionic villibetween the uterus and the placenta. Fetal cells inthe sample are used to construct a karyotype,which may reveal chromosomal abnormalities.

3. A sex-influenced trait is influenced by the pres-ence of sex hormones and its genes are not lo-cated on sex chromosomes, while a sex-linkedtrait is linked to a sex chromosome.

4. Children: type A, I Ai; type B, I Bi; type AB, I AI B; typeO, ii. One parent is type A, I Ai; the other parent istype B, I bi.

STRUCTURES AND FUNCTIONSX-linked recessive trait: one filled square, one opensquare, one half-filled circle, and one open circle.Autosomal recessive trait: one half-filled square, one open square, one half-filled circle, and one open circle.