Question 1

Which of the following best explains why males are more likely than females to express recessive X-linked genetic disorders, such as hemophilia?

Accepted Answer

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

Question 2

A woman who is heterozygous for a gene on the X chromosome has one of her X chromosomes inactivated in each cell, forming a Barr body. What is the biological significance of this process?

Accepted Answer

It ensures dosage compensation so that females do not produce twice as many X-linked gene products as males.

Question 3

Which chromosomal mutation would most likely result in a gene being present in extra copies, potentially leading to overexpression of that gene?

Accepted Answer

Duplication

Question 4

During DNA replication, which enzyme is responsible for joining Okazaki fragments on the lagging strand?

Accepted Answer

DNA ligase

Question 5

A scientist observes that after DNA replication, each new DNA molecule consists of one old strand and one new strand. This observation supports which model of DNA replication?

Accepted Answer

Semi-conservative replication

Question 6

Which of the following best describes the difference between DNA and RNA?

Accepted Answer

DNA contains deoxyribose sugar, while RNA contains ribose sugar.

Question 7

A mutation changes a codon from UAU (tyrosine) to UAA (stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 8

Which process occurs in the nucleus and results in the production of a pre-mRNA molecule?

Accepted Answer

Transcription

Question 9

A patient’s cells are found to have shortened telomeres. What is a likely consequence of this cellular condition?

Accepted Answer

The cells may lose genetic information and become prone to aging or apoptosis.

Question 10

Which of the following is an example of evidence supporting Darwin’s theory of evolution by natural selection?

Accepted Answer

Homologous structures in the limbs of mammals

Question 11

A population of beetles is exposed to a pesticide. Over several generations, most beetles are resistant to the pesticide. Which mechanism best explains this change?

Accepted Answer

Directional selection

Question 12

Which of the following equations represents the Hardy-Weinberg equilibrium for allele and genotype frequencies in a population?

Accepted Answer

$$p^2 + 2pq$$ + $$q^2 = 1$

Question 13

Which of the following is NOT a condition required for Hardy-Weinberg equilibrium?

Accepted Answer

Small population size

Question 14

A small group of finches colonizes a new island, and their allele frequencies differ from the original population. This is an example of:

Accepted Answer

Founder effect

Question 15

Which of the following best describes the central dogma of molecular biology?

Accepted Answer

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

Question 16

A gene is transcribed into mRNA, which is then processed by adding a 5’ cap and a poly-A tail. What is the primary function of these modifications?

Accepted Answer

They protect mRNA from degradation and assist in translation.

Question 17

A population experiences a drastic reduction in size due to a natural disaster, resulting in a loss of genetic diversity. This is an example of:

Accepted Answer

Bottleneck effect

Question 18

Which type of selection increases the frequency of individuals with extreme phenotypes at both ends of the spectrum?

Accepted Answer

Disruptive selection

Question 19

A mutation causes a shift in the reading frame of the genetic code, resulting in a completely different amino acid sequence downstream. What type of mutation is this?

Accepted Answer

Frameshift mutation

Question 20

Which gene is responsible for initiating male development in humans?

Accepted Answer

SRY gene

Key Concepts in Chromosomal Inheritance, DNA Replication, Gene Expression, and Evolution

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