Question 1

Which structure is responsible for condensing DNA into chromosomes during cell division, and what proteins are involved in this process?

Accepted Answer

Chromosome; histone proteins

Question 2

According to the chromosomal theory of inheritance, which statement best explains Mendel’s law of segregation?

Accepted Answer

Homologous chromosomes separate during meiosis, causing alleles to segregate

Question 3

In Thomas Hunt Morgan’s experiment with Drosophila, what was the significance of the white-eyed mutant male crossed with a wild-type female?

Accepted Answer

It provided evidence that the gene for eye color is located on the X chromosome

Question 4

If a female cat is heterozygous for fur color genes located on the X chromosome, what phenomenon explains the mosaic fur pattern observed in adult cats?

Accepted Answer

X chromosome inactivation

Question 5

Which equation represents the probability of a male offspring inheriting an X-linked recessive disorder if the mother is a carrier and the father is unaffected?

Accepted Answer

$$P = \frac{1}{2}$$

Question 6

What is the expected frequency of recombination between two genes located on different chromosomes?

Accepted Answer

$$50\%$$

Question 7

A child is born with three copies of chromosome 21. Which condition does this describe, and what is the chromosomal abnormality called?

Accepted Answer

Down syndrome; trisomy

Question 8

Which type of chromosomal alteration involves the reversal of a segment within a chromosome?

Accepted Answer

Inversion

Question 9

In a dihybrid cross involving genes on the same chromosome, what mechanism produces recombinant offspring?

Accepted Answer

Crossing over

Question 10

Which chromosomal system determines sex in humans, and what gene is responsible for male development?

Accepted Answer

X-Y system; SRY gene

Question 11

A female with only one X chromosome (X0) is diagnosed with which syndrome, and what is the viability of this monosomy?

Accepted Answer

Turner syndrome; viable

Question 12

Which equation describes the expected genotype ratio for offspring from a cross between a heterozygous female (XNXn) and a normal male (XNY) for an X-linked trait?

Accepted Answer

$$1\;XNXN : 1\;XNXn : 1\;XNY : 1\;XnY$$

Question 13

Which chromosomal alteration is most likely to result in a genetic disorder due to the loss of essential genes?

Accepted Answer

Deletion

Question 14

If nondisjunction occurs during meiosis I, what is the result in terms of chromosome number in the gametes?

Accepted Answer

Half the gametes will have an extra chromosome, and half will have one less

Question 15

Which statement best describes the inheritance pattern of X-linked recessive traits?

Accepted Answer

Males express the trait if they have one copy of the allele

Question 16

What is the physical basis for Mendel’s law of independent assortment?

Accepted Answer

Random orientation of homologous chromosome pairs during meiosis I

Question 17

Which equation represents the frequency of recombinant offspring for two genes that are completely linked?

Accepted Answer

$$0\%$$

Question 18

A male fruit fly with white eyes (mutant) is crossed with a female with red eyes (wild type). What is the expected phenotype of the F1 generation?

Accepted Answer

All offspring have red eyes

Question 19

Which chromosomal alteration involves the movement of a segment from one chromosome to another?

Accepted Answer

Translocation

Question 20

Which syndrome is associated with an individual having an extra X chromosome (XXY), and what is a common symptom?

Accepted Answer

Klinefelter syndrome; sterility

The Chromosomal Basis of Inheritance: Study Guide

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