Question 1

In mammals, a female is heterozygous for an X-linked recessive trait (e.g., color blindness). If she has children with a male who is not color blind, what is the probability that their son will be color blind?

Accepted Answer

$$0.25$$

Question 2

Which of the following best explains why genes that are close together on the same chromosome tend to be inherited together?

Accepted Answer

They are physically linked and less likely to be separated by crossing over during meiosis.

Question 3

A woman has two X chromosomes, but only one is active in each cell. What is the name of the inactivated X chromosome, and what is its significance?

Accepted Answer

Barr body; it ensures dosage compensation between males and females.

Question 4

A male fruit fly inherits a mutation on the Y chromosome. Which of the following statements is true about the inheritance of this mutation?

Accepted Answer

All of his sons will inherit the mutation.

Question 5

Which of the following is a consequence of nondisjunction during meiosis?

Accepted Answer

A gamete with an abnormal number of chromosomes, such as trisomy 21.

Question 6

A plant cell inherits a mutation in its chloroplast DNA. Which of the following best describes how this mutation will be inherited?

Accepted Answer

It will be inherited maternally, since chloroplasts are usually passed from the mother.

Question 7

According to Chargaff’s rules, if a DNA molecule contains $$30\%$$ adenine, what percentage of guanine does it contain?

Accepted Answer

$$20\%$$

Question 8

Which enzyme is responsible for synthesizing the RNA primer during DNA replication?

Accepted Answer

Primase

Question 9

During DNA replication, which direction does DNA polymerase synthesize the new strand?

Accepted Answer

From $$5' to$$ $$3'$$

Question 10

Which of the following best describes the function of telomeres?

Accepted Answer

They protect the ends of chromosomes from deterioration during replication.

Question 11

A DNA sequence $$5'	ext{-}ATGCGT-3' is $$transcribed into mRNA. What is the corresponding mRNA sequence?

Accepted Answer

$$5'	ext{-}AUGCGU-3'$$

Question 12

Which of the following mutations would most likely result in a truncated (shortened) protein?

Accepted Answer

Nonsense mutation

Question 13

Which of the following best explains why the genetic code is described as 'redundant but not ambiguous'?

Accepted Answer

Multiple codons can code for the same amino acid, but each codon codes for only one amino acid.

Question 14

A segment of DNA is mutated from $$5'	ext{-}TACGGA-3' to$$ $$5'	ext{-}TAGGGA-3'. $$What type of mutation is this, and what is its likely effect?

Accepted Answer

Nonsense mutation; it introduces a stop codon.

Question 15

Which of the following is NOT a function of DNA polymerase III in prokaryotic DNA replication?

Accepted Answer

Synthesizing the RNA primer

Question 16

A chromosomal inversion occurs. Which of the following best describes this event?

Accepted Answer

A segment of a chromosome is reversed end to end.

Question 17

Which of the following statements about viruses is correct?

Accepted Answer

Viruses require a host cell to replicate their genetic material.

Question 18

If a gene map shows two genes are $$10$$ map units apart, what does this indicate about their recombination frequency?

Accepted Answer

There is a $$10\%$$ chance of recombination between them.

Question 19

Which of the following best describes the role of DNA ligase during DNA replication?

Accepted Answer

It joins Okazaki fragments on the lagging strand.

Question 20

A patient is found to have a mitochondrial disorder. Which parent is most likely to have passed this disorder to the patient, and why?

Accepted Answer

The mother, because mitochondria are inherited maternally.

Genetics: Chromosomal Inheritance, DNA Replication, and Gene Expression

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