Q: Which of the following equations correctly represents the calculation of recombination frequency?

$$\text{Recombination frequency} = \frac{\text{Number of recombinant offspring}}{\text{Total number of offspring}} \times 100$$

Question 1

Which of the following best explains why sex-linked recessive disorders are more common in males than in females?

Accepted Answer

Males have only one X chromosome, so a single recessive allele will cause the disorder.

Question 2

A woman who is a carrier for hemophilia (an X-linked recessive disorder) marries a man with normal blood clotting. What is the probability that their son will have hemophilia?

Accepted Answer

$$0.25$$

Question 3

Which chromosomal alteration is associated with the 'cry of the cat' syndrome in humans?

Accepted Answer

Deletion on chromosome 5

Question 4

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

Accepted Answer

They are likely to be inherited together (linked).

Question 5

In a testcross between AaBb and aabb plants, if the genes are unlinked, what is the expected phenotypic ratio among the offspring?

Accepted Answer

$$1:1:1:1$$

Question 6

Which of the following chromosomal changes is most likely to result in infertility due to improper pairing during meiosis?

Accepted Answer

Inversion

Question 7

A male with Klinefelter syndrome has which of the following karyotypes?

Accepted Answer

$$47, XXY$$

Question 8

Which process during meiosis is responsible for the independent assortment of alleles?

Accepted Answer

Random alignment of homologous chromosomes during Metaphase I

Question 9

A woman with Turner syndrome has which chromosomal composition?

Accepted Answer

$$45, XO$$

Question 10

Which of the following best describes the result of nondisjunction during Anaphase I of meiosis?

Accepted Answer

Homologous chromosomes fail to separate, resulting in gametes with an abnormal number of chromosomes.

Question 11

Which of the following is a real-life example of a disease caused by a reciprocal translocation?

Accepted Answer

Chronic myelogenous leukemia

Question 12

A color-blind son is born to two parents with normal vision. What are the most likely genotypes of the parents?

Accepted Answer

Mother: $$X^N X^n$$, Father: $$X^N Y$$

Question 13

Which of the following best explains the patchy distribution of sweat glands in women with a genetic defect affecting sweat gland formation?

Accepted Answer

X chromosome inactivation

Question 14

If the recombination frequency between two genes is 50%, what does this indicate about their location?

Accepted Answer

They are on different chromosomes or far apart on the same chromosome.

Question 15

Which of the following is NOT a type of chromosomal alteration?

Accepted Answer

Replication

Question 16

A testcross between a dihybrid fly (BbVgvg) and a double mutant (bbvgvg) produces mostly parental-type offspring and very few recombinants. What does this suggest about the genes?

Accepted Answer

The genes are linked.

Question 17

Which of the following equations correctly represents the calculation of recombination frequency?

Accepted Answer

$$	ext{Recombination frequency} = \frac{	ext{Number of recombinant offspring}}{	ext{Total number of offspring}} 	imes 100$$

Question 18

Which of the following is true about X inactivation in female mammals?

Accepted Answer

One X chromosome is randomly inactivated in each cell during early embryogenesis.

Question 19

A woman with genotype $$X^D X^d ($$where $$X^D is $$the dominant normal allele and $$X^d is $$the recessive disease allele) is a carrier for a sex-linked disease. If she has children with a man with genotype $$X^D Y$$, what is the probability that a daughter will be a carrier?

Accepted Answer

$$0.25$$

The Chromosomal Basis of Inheritance

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