Question 1

According to the chromosome theory of inheritance, what is the relationship between genes and chromosomes?

Accepted Answer

Genes are located on chromosomes, and each chromosome carries many genes at specific loci.

Question 2

During meiosis, what event ensures the segregation of alleles for a gene?

Accepted Answer

Separation of homologous chromosomes during Anaphase I.

Question 3

A sexually reproducing animal has genotype HhTt for two unlinked genes. Which genotype is possible in a gamete from this organism?

Accepted Answer

HT

Question 4

Thomas Hunt Morgan’s experiments with Drosophila melanogaster provided the first scientific support for which theory?

Accepted Answer

Chromosome Theory of Inheritance

Question 5

In Morgan’s white-eyed fly cross, if the white-eye mutation was autosomal, what would be the expected outcome for male and female offspring?

Accepted Answer

Both males and females could have white eyes.

Question 6

Which of the following best explains why sex-linked diseases are more common in males?

Accepted Answer

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

Question 7

A female carrier for hemophilia (XDXd) marries a male with normal blood clotting (XDY). What fraction of their male children will have hemophilia?

Accepted Answer

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

Question 8

What is the probability that a human male will inherit an X-linked recessive allele from his father?

Accepted Answer

0%

Question 9

A genetic defect in humans results in the absence of sweat glands in the skin. In women, this defect is expressed in patches. What explains this pattern?

Accepted Answer

X chromosome inactivation

Question 10

Which of the following statements about X chromosome inactivation is correct?

Accepted Answer

It results in the formation of a Barr body in female cells.

Question 11

In a testcross using F1 dihybrid flies, if the percentages of parental and recombinant offspring are about the same, what does this indicate about the two genes?

Accepted Answer

The genes are unlinked.

Question 12

The recombination frequency between two gene loci is:

Accepted Answer

Greater as the distance between the two loci increases.

Question 13

In a testcross of AaBb x aabb, if the genes are unlinked, what is the expected phenotypic ratio among the offspring?

Accepted Answer

1:1:1:1

Question 14

If 900 offspring are produced from a testcross of AaBb x aabb and the genes are unlinked, how many offspring would you expect for each phenotype?

Accepted Answer

225

Question 15

Which chromosomal alteration is associated with Huntington’s disease due to repeated AGC sequences?

Accepted Answer

Duplication

Question 16

A child is born with a missing chromosome (2n-1). What is this condition called?

Accepted Answer

Monosomy

Question 17

Which chromosomal abnormality is responsible for Down Syndrome?

Accepted Answer

Trisomy 21

Question 18

Which event during meiosis can lead to aneuploidy?

Accepted Answer

Nondisjunction during Anaphase I or II

Question 19

Which syndrome is characterized by an XO genotype and results in a female with short stature and underdeveloped ovaries?

Accepted Answer

Turner Syndrome

Question 20

Which chromosomal alteration involves a segment of a chromosome being oriented in the reverse direction and is associated with acute myeloid leukemia?

Accepted Answer

Inversion

The Chromosomal Basis of Inheritance

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