Question 1

A woman who is a carrier for a recessive X-linked disorder (X	extsuperscript{N}X	extsuperscript{n}) and a man who does not have the disorder (X	extsuperscript{N}Y) have a child. What is the probability that their son will have the disorder?

Accepted Answer

$$0.25$$

Question 2

Which of the following best explains why males are more likely than females to express recessive X-linked traits?

Accepted Answer

Males have only one X chromosome, so a single recessive allele will be expressed.

Question 3

A plant with red flowers (RR) is crossed with a plant with white flowers (WW). All offspring have pink flowers. What type of inheritance is this an example of?

Accepted Answer

Incomplete dominance

Question 4

Which of the following statements about DNA replication is correct?

Accepted Answer

DNA replication is semiconservative, producing two molecules each with one old and one new strand.

Question 5

A point mutation changes a codon from UAU to UAA. What is the most likely effect on the protein?

Accepted Answer

A nonsense mutation resulting in a premature stop codon.

Question 6

Which of the following best describes the role of telomerase in eukaryotic cells?

Accepted Answer

It adds repetitive DNA sequences to the ends of chromosomes, preventing shortening during replication.

Question 7

A researcher observes that a certain gene is not expressed in skin cells but is highly expressed in neurons. Which of the following mechanisms is most likely responsible for this difference?

Accepted Answer

Differential patterns of epigenetic tags and transcription factors

Question 8

Which of the following is true regarding the lac operon in E. coli?

Accepted Answer

Lactose binds to the repressor, causing it to release from the operator and allowing transcription.

Question 9

Which of the following best explains why lethal recessive alleles are more common in populations than lethal dominant alleles?

Accepted Answer

Carriers (heterozygotes) can pass on lethal recessive alleles without being affected.

Question 10

A pedigree shows a trait that appears in every generation and affects both males and females equally. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 11

Which of the following is a direct result of the independent assortment of chromosomes during meiosis?

Accepted Answer

Increased genetic variation in gametes

Question 12

Which of the following best describes the effect of a frameshift mutation near the beginning of a gene?

Accepted Answer

It likely results in a nonfunctional protein due to alteration of all downstream amino acids.

Question 13

Which of the following statements about the central dogma of molecular biology is correct?

Accepted Answer

DNA is transcribed into RNA, which is then translated into protein.

Question 14

A scientist introduces a eukaryotic gene containing introns into a bacterial cell. The gene is not expressed properly. What is the most likely reason?

Accepted Answer

Bacteria lack the machinery to remove introns from pre-mRNA.

Question 15

Which of the following is a function of the 5' cap and poly(A) tail added to eukaryotic mRNA?

Accepted Answer

They help bind ribosomes and protect mRNA from degradation.

Question 16

Which of the following best describes the effect of methylation on gene expression in eukaryotes?

Accepted Answer

Methylation generally condenses chromatin, making genes less accessible for transcription.

Question 17

A mutation in a gene results in a protein that is missing several amino acids but is otherwise unchanged. Which type of mutation most likely occurred?

Accepted Answer

A deletion of one or more entire codons

Question 18

Which of the following is true about codons and the genetic code?

Accepted Answer

Some amino acids are coded for by more than one codon.

Question 19

Which of the following is a key difference between prokaryotic and eukaryotic gene expression?

Accepted Answer

Eukaryotes process pre-mRNA by splicing out introns and adding a 5' cap and poly(A) tail.

Question 20

Which of the following best describes the role of alternative splicing in eukaryotes?

Accepted Answer

It allows a single gene to code for multiple related proteins.

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