Question 1

How did the improvement of microscopy techniques in the late 1800s set the stage for the emergence of modern genetics?

Accepted Answer

It allowed the study of meiosis and mitosis, revealing parallels between behaviors of the Mendelian concept of the gene and the movement/pairing of chromosomes.

Question 2

In some species of Drosophila, there are genes on the Y chromosome that are not on the X chromosome. Imagine that a particular allele is on the Y chromosome and reduces the size by half of individuals with the new allele. Which of the following statements is accurate with regard to this situation?

Accepted Answer

This allele is passed to all male but no female offspring of a male with the allele.

Question 3

In Drosophila, white eyes are due to an X-linked recessive allele (X^w). Which of the following crosses could NOT result in a white-eyed Drosophila male?

Accepted Answer

Homozygous red-eyed females with white-eyed males

Question 4

What is the relationship between recombination frequency and the physical distance between genes on chromosomes?

Accepted Answer

The closer two genes are, the lower the recombination frequency.

Question 5

Nondisjunction can happen in either meiosis I or meiosis II. Consider $$n + 1$$ and $$n - 1$$ gametes involving chromosome 21 and reflect on nondisjunction in meiosis I and meiosis II. Select the best comparative statement.

Accepted Answer

A $$n + 1$$ gamete can be different depending on whether nondisjunction happened in meiosis I or meiosis II.

Question 6

A woman who is heterozygous for an X-linked recessive disorder has children with a man who does not have the disorder. What is the probability that their son will have the disorder?

Accepted Answer

$$0.50$$

Question 7

If two genes are located very close together on the same chromosome, which of the following is most likely true?

Accepted Answer

They will be inherited together more often than not.

Question 8

Which of the following best explains why males are more likely than females to express X-linked recessive traits?

Accepted Answer

Males only need one copy of the allele to express the trait.

Question 9

A geneticist observes that two genes have a recombination frequency of $$10\%. $$What does this indicate about the genes?

Accepted Answer

They are located close together on the same chromosome.

Question 10

Which of the following is a direct result of nondisjunction during meiosis?

Accepted Answer

Production of gametes with abnormal numbers of chromosomes

Study Guide: Chromosomal Basis of Inheritance (General Biology)

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