Question 1

Which of the following best explains why Thomas Hunt Morgan was able to correlate the inheritance of the eye color gene in Drosophila with the behavior of sex chromosomes?

Accepted Answer

The X and Y chromosomes differ in size and gene content, allowing Morgan to observe that the eye color gene was X-linked and inherited differently in males and females.

Question 2

Why are males more likely than females to express X-linked recessive disorders such as color blindness?

Accepted Answer

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

Question 3

In the context of genetic linkage, why do genes that are farther apart on the same chromosome show a higher frequency of recombination?

Accepted Answer

Crossing over is more likely to occur between genes that are farther apart, increasing the chance of recombination.

Question 4

A geneticist observes that two genes have a recombination frequency of 50%. What does this indicate about the genes?

Accepted Answer

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

Question 5

Which chromosomal alteration is most likely to result in Down syndrome?

Accepted Answer

Trisomy of chromosome 21

Question 6

A woman who is a carrier for an X-linked recessive disorder and a man who does not have the disorder have a child. What is the probability that their son will have the disorder?

Accepted Answer

$$0.50$$

Question 7

Which of the following best describes a Barr body?

Accepted Answer

A condensed, inactivated X chromosome found in the nuclei of female mammalian cells.

Question 8

Which of the following is an example of a non-Mendelian inheritance pattern?

Accepted Answer

Genomic imprinting, where the expression of an allele depends on the parent of origin

Question 9

A child inherits a mitochondrial disorder. Which parent most likely transmitted the disorder?

Accepted Answer

Mother

Question 10

Which of the following chromosomal changes is least likely to be lethal and why?

Accepted Answer

Inversion, because all genes are still present, just in a reversed order.

Question 11

If a cell has a chromosome number of $$2n+1$$, what is this condition called?

Accepted Answer

Trisomy

Question 12

Which of the following best explains why reciprocal translocations are often less harmful than deletions?

Accepted Answer

Reciprocal translocations do not change the overall amount of genetic material.

Question 13

A scientist is mapping genes on a chromosome and finds that the recombination frequency between gene A and gene B is 10%, and between gene B and gene C is 5%. What can be inferred about the relative positions of these genes?

Accepted Answer

Gene B is between gene A and gene C.

Question 14

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

Accepted Answer

Aneuploidy, such as trisomy or monosomy

Question 15

Which of the following best describes the inheritance of chloroplast DNA in most plants?

Accepted Answer

It is inherited only from the maternal parent.

Question 16

A genetic counselor is explaining to a couple that their child has a disorder caused by a deletion on chromosome 5. Which of the following best describes this type of chromosomal alteration?

Accepted Answer

A segment of the chromosome is missing.

Question 17

Which of the following scenarios is an example of polyploidy?

Accepted Answer

A plant cell with three complete sets of chromosomes ($$3n)$$

Question 18

Which of the following is true about the inheritance of traits controlled by mitochondrial genes?

Accepted Answer

They are inherited only from the mother.

Question 19

Which of the following best explains why genomic imprinting is considered an exception to standard Mendelian inheritance?

Accepted Answer

The expression of an allele depends on whether it was inherited from the mother or the father.

Question 20

A patient is diagnosed with a cancer associated with a chromosomal translocation. Which of the following best describes a translocation?

Accepted Answer

A segment of one chromosome is moved to a nonhomologous chromosome.

Chromosomal Basis of Inheritance: Key Concepts and Patterns

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