Question 1

Which of the following best explains how the chromosomal theory of inheritance provides a physical basis for Mendelian inheritance?

Accepted Answer

Genes are located on chromosomes, and the behavior of chromosomes during meiosis accounts for inheritance patterns.

Question 2

A female fruit fly with genotype $$w^+w is $$crossed with a male with genotype $$wY. $$What is the expected phenotypic ratio for eye color in the offspring?

Accepted Answer

All offspring will have red eyes.

Question 3

Which law of Mendel is illustrated when each resultant gamete has one of each homologous chromosome pair?

Accepted Answer

Law of Independent Assortment

Question 4

What is the definition of a sex-linked gene?

Accepted Answer

A gene located on either the X or Y chromosome.

Question 5

Which of the following is a human X-linked disorder?

Accepted Answer

Hemophilia

Question 6

If a woman who is a carrier for color-blindness (X$$^NX$^n) $$has children with a man who has normal vision (X$$^NY$$), what is the probability that a son will be color-blind?

Accepted Answer

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

Question 7

What is a Barr body?

Accepted Answer

An inactivated X chromosome in a female cell.

Question 8

Linked genes are:

Accepted Answer

Genes located close together on the same chromosome and tend to be inherited together.

Question 9

What is a map unit (centimorgan) in genetic mapping?

Accepted Answer

A unit representing a 1% recombination frequency between two genes.

Question 10

If the recombination frequency between two genes is 12%, how many map units apart are they?

Accepted Answer

$$12$$ map units

Question 11

What is nondisjunction?

Accepted Answer

The failure of homologous chromosomes or sister chromatids to separate properly during meiosis.

Question 12

Which of the following is a characteristic of Down syndrome?

Accepted Answer

Trisomy 21

Question 13

A male with Klinefelter syndrome has which karyotype?

Accepted Answer

XXY

Question 14

Which event during meiosis increases genetic variation by producing new combinations of alleles?

Accepted Answer

Crossing over

Question 15

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

Accepted Answer

Alleles of genes on nonhomologous chromosomes assort independently during gamete formation.

Question 16

If a female is heterozygous for a gene on the X chromosome and a male is hemizygous, what is the expected ratio of phenotypes in their offspring?

Accepted Answer

1:1

Question 17

Which of the following is an example of aneuploidy?

Accepted Answer

A human cell with 47 chromosomes due to an extra chromosome 21.

Question 18

What is the physical basis for the independent assortment of alleles?

Accepted Answer

The random orientation of homologous chromosome pairs during metaphase I of meiosis.

Question 19

Which of the following best describes polyploidy?

Accepted Answer

The presence of more than two complete sets of chromosomes in an organism.

Question 20

Which of the following is a possible result of a chromosomal deletion?

Accepted Answer

Loss of genetic material and possible genetic disorders.

Chapter 12: The Chromosomal Basis of Inheritance – Study Guide

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