Exam 15: The Chromosomal Basis of Inheritance

A man who is a dwarf with achondroplasia and normal vision marries a color-blind woman of normal height. The man's father was six feet tall, and both the woman's parents were of average height. Dwarfism caused by achondroplasia is autosomal dominant, and red-green color blindness is X-linked recessive. What proportion of their sons would be color blind and of normal height?

Use the following information to answer the question. A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele (a)of gene A; a feathered stem, due to an allele (b)of gene B; and hollow roots due to an allele (c)of gene C. The three genes are linked and recombine. A geneticist performed a testcross with an organism that had been found to be heterozygous for the three recessive traits, and she was able to identify progeny of the following phenotypic distribution (+ = wild type): Phenotypes Leaves Stems Roots Number 1 a + + 14 2 a + c 0 3 a b + 32 4 a b c 440 5 + b + 0 6 + b c 16 7 + + c 28 8 + + + 470 Total 1000 Which of the following are the phenotypes of the parents in this cross?

Why are males more often affected by sex-linked traits than females?

Use the following figure to answer the question. The pedigree in the figure shows the transmission of a trait in a particular family. Based on this pattern of transmission, the trait is most likely ________.

Use the following information to answer the question. Sex Phenotype Number male wild 123 male yellow 116 female wild 240 In a Drosophila experiment, a cross was made between homozygous wild-type females and yellow-bodied males. All of the resulting F?s were phenotypically wild type. However, adult flies of the F? generation (resulting from matings of the F?s)had the characteristics shown in the figure. How is the mutant allele for yellow body inherited?

Use the following information to answer the question. A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele (a)of gene A; a feathered stem, due to an allele (b)of gene B; and hollow roots due to an allele (c)of gene C. The three genes are linked and recombine. A geneticist performed a testcross with an organism that had been found to be heterozygous for the three recessive traits, and she was able to identify progeny of the following phenotypic distribution (+ = wild type): Phenotypes Leaves Stems Roots Number 1 a + + 14 2 a + c 0 3 a b + 32 4 a b c 440 5 + b + 0 6 + b c 16 7 + + c 28 8 + + + 470 Total 1000 If recombination frequency is equal to distance in map units, what is the approximate distance between genes A and B?

Genomic imprinting is generally due to the addition of methyl (-CH₃)groups to C nucleotides and chemical histone changes to silence a given gene. If this depends on the sex of the parent who transmits the gene, which of the following statements must be true?

Which of the following phrases correctly defines what one map unit is?

Use the following information to answer the question. A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish leaves, due to an allele (a)of gene A; a feathered stem, due to an allele (b)of gene B; and hollow roots due to an allele (c)of gene C. The three genes are linked and recombine. A geneticist performed a testcross with an organism that had been found to be heterozygous for the three recessive traits, and she was able to identify progeny of the following phenotypic distribution (+ = wild type): Phenotypes Leaves Stems Roots Number 1 a + + 14 2 a + c 0 3 a b + 32 4 a b c 440 5 + b + 0 6 + b c 16 7 + + c 28 8 + + + 470 Total 1000 The greatest distance among the three genes is between a and c. What does this mean?

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?

Use the following information to answer the question. Sex Phenotype Number male wild 123 male yellow 116 female wild 240 In a Drosophila experiment, a cross was made between homozygous wild-type females and yellow-bodied males. All of the resulting F?s were phenotypically wild type. However, adult flies of the F? generation (resulting from matings of the F?s)had the characteristics shown in the figure. How is the mutant allele for yellow body inherited?

A phenotypically normal prospective couple seeks genetic counseling because the man knows that he has a translocation of a portion of his chromosome 4, which has been exchanged with a portion of his chromosome 12. Although his translocation is balanced, he and his wife want to know the probability that his sperm will be abnormal. What is your prognosis regarding his sperm?

Which of the following is an example of monosomy in humans?

Cinnabar eye color is a sex-linked, recessive characteristic in fruit flies. If a female having cinnabar eyes is crossed with a wild-type male, what percentage of the F₁ males will have cinnabar eyes?

Which of the following statements would explain a testcross involving F₁ dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced?

The SRY gene is best described as ________.

During meiosis, a defect occurs in a cell that results in the failure of spindle microtubules binding at the kinetochores. Which of the following statements describes the most likely result of such a defect?

A recessive allele on the X chromosome is responsible for red-green color blindness in humans. A woman with normal vision whose father is color blind marries a color-blind male. What is the probability that this couple's first son will be color blind?

Which of the following correctly describes a Philadelphia chromosome?

Mitochondrial DNA is primarily involved in coding for proteins needed for protein complexes of the electron transport chain and ATP synthase. Therefore, mutations in mitochondrial genes would most affect which of the following processes?