Question 1

A human cell has a diploid number of 46 chromosomes. How many chromosomes would you expect to find in a human gamete after meiosis?

Accepted Answer

23

Question 2

Which of the following events occurs only during meiosis and not during mitosis?

Accepted Answer

Pairing of homologous chromosomes and crossing over

Question 3

Independent assortment of chromosomes is a result of which of the following?

Accepted Answer

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

Question 4

A cell is observed under a microscope with homologous chromosomes aligned in pairs at the metaphase plate. Which stage is this cell in?

Accepted Answer

Metaphase I of meiosis

Question 5

Mendel’s law of segregation is best explained by which event during meiosis?

Accepted Answer

Separation of homologous chromosomes during anaphase I

Question 6

In a cross between two heterozygous pea plants (Yy), what is the probability that an offspring will be homozygous recessive (yy)? Use the multiplication rule.

Accepted Answer

$$0.25$$

Question 7

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene causing multiple symptoms in cystic fibrosis

Question 8

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

Accepted Answer

$$0.5$$

Question 9

Which of the following best describes the chromosomal basis of inheritance as demonstrated by Thomas Hunt Morgan’s experiments with fruit flies?

Accepted Answer

Genes are located on chromosomes, and specific genes can be mapped to specific chromosomes

Question 10

What is the significance of a recombination frequency of 50% between two genes?

Accepted Answer

The genes are likely located on different chromosomes or far apart on the same chromosome

Question 11

Which chromosomal abnormality results from nondisjunction during meiosis II?

Accepted Answer

Some gametes have an extra chromosome, and some are missing one, but only half are affected

Question 12

A calico cat is almost always female because:

Accepted Answer

X inactivation leads to mosaic expression of coat color genes

Question 13

Which of the following is an example of epistasis?

Accepted Answer

A gene for pigment deposition masking the effect of a gene for pigment color in Labrador retrievers

Question 14

If a DNA sample contains 30% adenine, according to Chargaff’s rules, what percentage of guanine would you expect?

Accepted Answer

$$20\%$$

Question 15

Which of the following best describes the antiparallel structure of DNA?

Accepted Answer

The two strands run in opposite directions: one from $$5' to$$ $$3'$$, the other from $$3' to$$ $$5'$$

Question 16

Which enzyme is responsible for unwinding the DNA double helix during replication?

Accepted Answer

Helicase

Question 17

A child is born with Klinefelter syndrome (XXY). Which of the following best explains how this chromosomal abnormality could have occurred?

Accepted Answer

Nondisjunction of sex chromosomes during meiosis in one parent

Question 18

Which of the following is true about genomic imprinting?

Accepted Answer

It results in the expression of only one allele of a gene, depending on the parent of origin

Question 19

Which of the following best explains why mitochondrial diseases are inherited maternally?

Accepted Answer

Mitochondria are inherited almost exclusively from the egg cytoplasm

Question 20

During DNA replication, why are Okazaki fragments formed on the lagging strand?

Accepted Answer

DNA polymerase can only synthesize DNA in the $$5' \rightarrow 3'$$ direction, so the lagging strand is synthesized discontinuously

Study Guide: Genetics and the Molecular Basis of Inheritance (Chapters 13–16)

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