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Exam 15: The Chromosomal Basis of Inheritance

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Question 21

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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?

A) The two genes are closely linked on the same chromosome.
B) The two genes are linked but on different chromosomes.
C) Recombination did not occur in the cell during meiosis.
D) Both of the characters are controlled by more than one gene.

E) All of the above
F) A) and D)

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Question 22

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Which of the following correctly describes a Philadelphia chromosome?

A) a human chromosome 22 that has had a specific translocation
B) a human chromosome 9 that is found only in one type of cancer
C) an animal chromosome found primarily in the mid-Atlantic area of the United States
D) a chromosome found only in mitochondria

E) A) and B)
F) All of the above

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Question 23

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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) : The greatest distance among the three genes is between a and c. What does this mean?

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) : Which of the progeny phenotypes will require recombination between genes A and B?

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?

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) : What is the greatest benefit of having used a testcross for this experiment?

Use the following information to answer the question. In a Drosophila experiment, a cross was made between homozygous wild-type females and yellow-bodied males. All of the resulting F₁s were phenotypically wild type. However, adult flies of the F₂ generation (resulting from matings of the F₁s) had the characteristics shown in the figure. How is the mutant allele for yellow body inherited?

A couple has a child with Down syndrome. The mother is 39 years old at the time of delivery. Which of the following is the most probable cause of the child's condition?

Which of the following individuals will inherit an X-linked allele from a man who carries it?

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?

Red-green color blindness is a sex-linked recessive trait in humans. Two people with normal color vision have a color-blind son. What are the genotypes of the parents?

What is an adaptive advantage of recombination between linked genes?

Abnormal chromosomes are frequently found in malignant tumors. Errors such as translocations may place a gene in close proximity to different control regions. Which of the following events might then occur to make the cancer worse?

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?

The SRY gene is best described as ________.

If cell X enters meiosis, and nondisjunction of one chromosome occurs in one of its daughter cells during meiosis II, how will this affect the gametes at the completion of meiosis?

What is a syndrome?

Map units on a linkage map cannot be relied upon to calculate physical distances on a chromosome for which of the following reasons?

Sex determination in mammals is due to the SRY gene found on the Y chromosome. Which of the following situations could allow a person with an XX karyotype to develop a male phenotype?

Pseudohypertrophic muscular dystrophy is a human disorder that causes gradual deterioration of the muscles. Only boys are affected, and they are always born to phenotypically normal parents. Due to the severity of the disease, the boys die in their teens. Is this disorder likely to be caused by a dominant or recessive allele? Is the inheritance of this trait sex-linked or autosomal?