Q: A fruit fly cross yields the following offspring: 721 gray normal, 751 black vestigial, 49 gray vestigial, and 45 black normal. What is the recombination frequency between the two genes?

$$\frac{49+45}{721+751+49+45} \times 100 = 6\%$$

Question 1

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

Accepted Answer

Males only need one copy of the mutant allele on their single X chromosome to express the disorder.

Question 2

A woman who is a carrier for red-green color blindness (an X-linked recessive trait) and a man with normal vision have a son. What is the probability that their son will be color blind?

Accepted Answer

$$\frac{1}{2}$$

Question 3

Which chromosomal alteration is most likely responsible for Cri du chat syndrome?

Accepted Answer

Deletion of a portion of chromosome 5

Question 4

If a gene is located on the Y chromosome, which of the following statements is true about its inheritance?

Accepted Answer

It is only inherited by sons from their fathers.

Question 5

A fruit fly cross yields the following offspring: 721 gray normal, 751 black vestigial, 49 gray vestigial, and 45 black normal. What is the recombination frequency between the two genes?

Accepted Answer

$$\frac{49+45}{721+751+49+45} 	imes 100 = 6\%$$

Question 6

Which chromosomal event leads to Down syndrome in humans?

Accepted Answer

Nondisjunction resulting in trisomy 21

Question 7

What is the function of the XIST gene in XX-females?

Accepted Answer

It inactivates one X chromosome, forming a Barr body.

Question 8

Which of the following best describes a translocation?

Accepted Answer

A segment of one chromosome is moved to a non-homologous chromosome.

Question 9

In a dihybrid cross involving linked genes, which outcome would indicate that crossing over has occurred?

Accepted Answer

Some offspring show recombinant phenotypes not seen in the parents.

Question 10

A male calico cat is extremely rare. Which genetic event could explain its existence?

Accepted Answer

The cat is XXY due to nondisjunction.

Question 11

Which of the following is true about the inheritance of Fragile X syndrome?

Accepted Answer

It is an X-linked dominant disorder.

Question 12

If a chromosome undergoes inversion, what is the most likely consequence?

Accepted Answer

A segment is reversed, potentially disrupting gene function.

Question 13

Which equation correctly calculates the recombination frequency between two genes?

Accepted Answer

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

Question 14

A woman with Klinefelter's syndrome has which of the following chromosomal compositions?

Accepted Answer

XXX

Question 15

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

Accepted Answer

Formation of gametes with abnormal chromosome numbers

Question 16

Which of the following best describes the law of independent assortment?

Accepted Answer

Alleles for different genes segregate independently during gamete formation.

Question 17

A patient is diagnosed with chronic myelogenous leukemia (CML). Which chromosomal event is most likely responsible?

Accepted Answer

Translocation between chromosomes 9 and 22

Question 18

Which of the following is true about linked genes?

Accepted Answer

They tend to be inherited together because they are physically close on the same chromosome.

Question 19

Which of the following is a parental type offspring in a linked gene cross?

Accepted Answer

An offspring with a phenotype matching one of the original parents

Question 20

Which chromosomal alteration is most likely to result in a fusion gene that causes uncontrolled cell growth?

Accepted Answer

Translocation

Chapter 12: Chromosomal Basis of Inheritance – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards