Genetics Chapter 15

A man with hemophilia (a recessive, sex-linked condition) has a daughter of normal phenotype. She marries a man who is normal for the trait. What is the probability that a daughter of this mating will be a hemophiliac? Express your answer as a fraction using the slash symbol and no spaces (for example, 1/24), or as a whole number.

0

A man with hemophilia (a recessive, sex-linked condition) has a daughter of normal phenotype. She marries a man who is normal for the trait. If the couple has four sons, what is the probability that all four will be born with hemophilia? Express your answer as a fraction (for example, 1/24), or as a whole number.

1/16

A man with hemophilia (a recessive, sex-linked condition) has a daughter of normal phenotype. She marries a man who is normal for the trait. What is the probability that a son will be a hemophiliac? Express your answer as a fraction (for example, 1/24), or as a whole number.

1/2

Red-green color blindness is caused by a sex-linked recessive allele. A color-blind man marries a woman with normal vision whose father was color-blind. What is the probability that their first son will be color-blind? Express your answer as a fraction using the slash symbol and no spaces (for example, 1/24).

1/2

Red-green color blindness is caused by a sex-linked recessive allele. A color-blind man marries a woman with normal vision whose father was color-blind. What is the probability that they will have a color-blind daughter? Express your answer as a fraction using the slash symbol and no spaces (for example, 1/24).

1/4

For tall heterozygotes with antennae, the offspring are: tall-antennae 46 dwarf-antennae 7 dwarf-no antennae 42 tall-no antennae 5 Calculate the recombination frequency between T and A. Enter your answer as a percentage (for example, 10%).

12%

A wild-type fruit fly (heterozygous for gray body color and normal wings) is mated with a black fly with vestigial wings. The offspring have the following phenotypic distribution: wild-type 778 black-vestigial 785 black-normal 158 gray-vestigial 162 What is the recombination frequency between these genes for body color and wing size? Express your answer as a percentage.

17

Two genes of a flower, one controlling blue (B) versus white (b) petals and the other controlling round (R) versus oval (r) stamens, are linked and are 10 map units apart. You cross a homozygous blue-oval plant with a homozygous white-round plant. The resulting F1 progeny are crossed with homozygous white-oval plants, and 1,000 F2 progeny are obtained. How many F2 plants of each of the four phenotypes do you expect? _____ blue-oval : _____ white-round : _____ blue-round : _____ white-oval Express your answer as four whole numbers separated by colons (for example, 400:300:200:100).

450:450:50:50

Assume that genes A and B are on the same chromosome and are 50 map units apart. An animal heterozygous at both loci is crossed with one that is homozygous recessive at both loci. What percentage of the offspring will show recombinant phenotypes resulting from crossovers?

50%

A wild-type fruit fly (heterozygous for gray body color and red eyes) is mated with a black fruit fly with purple eyes. The offspring are: wild-type 721 black-purple 751 gray-purple 49 black-red 45 What is the recombination frequency between these genes for body color and eye color? Express your answer as a percentage.

6%

A white-eyed female Drosophila is crossed with a red-eyed male Drosophila. Which statement below correctly describes the results? A. None of the females will have white eyes. B. Twenty-five percent of the females will have red eyes. C. None of the females will have red eyes. D. Twenty-five percent of the females will have white eyes. E. Fifty percent of the females will have red eyes.

A. None of the females will have white eyes.

Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel's law of segregation? A. The two alleles for each gene separate as homologous chromosomes move apart during anaphase I. B. Sister chromatids separate during anaphase II. C. The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs.

A. The two alleles for each gene separate as homologous chromosomes move apart during anaphase I.

2) Sturtevant provided genetic evidence for the existence of four pairs of chromosomes in Drosophila in which of these ways? A) There are four major functional classes of genes in Drosophila. B) Drosophila genes cluster into four distinct groups of linked genes. C) The overall number of genes in Drosophila is a multiple of four. D) The entire Drosophila genome has approximately 400 map units. E) Drosophila genes have, on average, four different alleles.

B) Drosophila genes cluster into four distinct groups of linked genes.

When Thomas Hunt Morgan crossed his red-eyed F1 generation flies to each other, the F2 generation included both red- and white-eyed flies. Remarkably, all the white-eyed flies were male. What was the explanation for this result? A) The gene involved is on the Y chromosome. B) The gene involved is on the X chromosome. C) The gene involved is on an autosome, but only in males. D) Other male-specific factors influence eye color in flies. E) Other female-specific factors influence eye color in flies.

B) The gene involved is on the X chromosome.

What can we observe in order to visualize Mendel's Law of Segregation? A. sister chromatids separating during mitosis B. homologous chromosomes separating during meiosis I C. the replication of DNA D. homologous chromosomes separating during meiosis II E. the behavior of sex-linked genes

B. homologous chromosomes separating during meiosis I

Imagine a human disorder that is inherited as a dominant, X-linked trait. How would the frequency of this disorder vary between males and females? A. Males and females would display this disorder with equal frequency. B. Males would display this disorder with greater frequency than females. C. Females would display this disorder with greater frequency than males.

C. Females would display this disorder with greater frequency than males.

Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel's law of independent assortment? A. Sister chromatids separate during anaphase II. B. The two alleles for each gene separate as homologous chromosomes move apart during anaphase I. C. The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs.

C. The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs.

Select the correct statement(s) about sex determination in animals. A. In all animals, males have the SRY gene and females lack this gene. B. In all animals, males are XY and females are XX. C. The mechanism of sex determination varies with different animal species.

C. The mechanism of sex determination varies with different animal species.

Determine the sequence of genes along a chromosome based on the following recombination frequencies: A−B 8 map units A−C 28 map units A−D 25 map units B−C 20 map units B−D 33 map units Select the correct order of genes along the chromosome.

D-A-B-C

What pattern of inheritance would lead a geneticist to suspect that an inherited disorder of cell metabolism is due to a defective mitochondrial gene? A. The disorder would only affect boys. B. The disorder would only affect girls. C. The disorder would always be inherited from the father. D. The disorder would always be inherited from the mother.

D. The disorder would always be inherited from the mother.

What name is given to the most common phenotype in a natural population? A. mutant phenotype B. locus C. genotype D. wild type E. autosome

D. wild type

Gregor Mendel set up a dihybrid cross with one pea plant from the parental generation (P) producing round yellow peas and the other pea plant producing wrinkled green peas. The F2 generation included 315 plants producing round yellow peas, 108 with round green peas, 101 with wrinkled yellow peas, and 32 with wrinkled green peas. How would these results have differed if pea shape and pea color had been linked genes, located close together on the same chromosome? a) The F2 generation would have included a higher percentage of pea plants producing round, yellow peas. b) The F2 generation would have included a higher percentage of pea plants producing yellow peas. c) The F2 generation would have included a lower percentage of pea plants producing wrinkled, green peas.

a) The F2 generation would have included a higher percentage of pea plants producing round, yellow peas.