Question 1

During which phase of mitosis do the chromosomes align at the center of the cell, and what is the significance of this alignment?

Accepted Answer

Metaphase; it ensures that each daughter cell receives an identical set of chromosomes.

Question 2

A cell with 2n = 46 chromosomes undergoes meiosis. How many chromosomes will each daughter cell have after meiosis II, and why?

Accepted Answer

23 chromosomes; because meiosis reduces the chromosome number by half, producing haploid gametes.

Question 3

Which of the following best explains why x-linked recessive disorders are more common in males than females?

Accepted Answer

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

Question 4

A plant with genotype $$AaBb is $$crossed with another plant with genotype $$aabb. $$What is the expected phenotypic ratio in the offspring if the genes are unlinked?

Accepted Answer

1:1:1:1

Question 5

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

Accepted Answer

Helicase

Question 6

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

Accepted Answer

Nonsense mutation

Question 7

Which of the following mechanisms contributes most directly to genetic variation during meiosis?

Accepted Answer

Crossing over during Prophase I

Question 8

In Mendel’s experiments, crossing two true-breeding pea plants (one with purple flowers and one with white flowers) resulted in all purple flowers in the F1 generation. What does this demonstrate?

Accepted Answer

The purple flower trait is dominant over the white flower trait.

Question 9

Which of the following best describes the semiconservative model of DNA replication?

Accepted Answer

Each new DNA molecule consists of one old strand and one new strand.

Question 10

A woman with genotype $$X^NX^n ($$where $$N is $$normal and $$n is a $$recessive allele for color blindness) has a child with a man who is $$X^nY. $$What is the probability that their son will be color blind?

Accepted Answer

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

Question 11

Which of the following is a real-life example of pleiotropy?

Accepted Answer

Sickle cell disease, where a single gene affects multiple traits such as anemia and resistance to malaria.

Question 12

Which process occurs in prokaryotes but not in eukaryotes during gene expression?

Accepted Answer

Transcription and translation occur simultaneously in the cytoplasm.

Question 13

Which of the following best describes the function of tRNA during translation?

Accepted Answer

tRNA brings amino acids to the ribosome and matches them to the mRNA codons via its anticodon.

Question 14

A cell is observed to have a cleavage furrow during cytokinesis. What type of cell is it most likely to be?

Accepted Answer

Animal cell

Question 15

Which of the following is NOT a mechanism that contributes to genetic variation in sexually reproducing organisms?

Accepted Answer

Binary fission

Question 16

Which scientist’s experiment with bacteriophages demonstrated that DNA, not protein, is the genetic material?

Accepted Answer

Hershey and Chase

Question 17

A person with Down Syndrome has three copies of chromosome 21. What is the term for this chromosomal abnormality?

Accepted Answer

Trisomy

Question 18

Which of the following best explains why mitochondrial DNA is inherited only from the mother?

Accepted Answer

The egg provides the majority of cytoplasm and organelles, including mitochondria, to the zygote.

Question 19

Which of the following best describes the law of segregation?

Accepted Answer

Alleles for a trait separate during gamete formation so each gamete carries only one allele.

Question 20

A DNA sample has 30% adenine. According to Chargaff’s rules, what percentage of guanine should be present?

Accepted Answer

20%

BIO 101 Exam 3 Study Guide: Cell Cycle, Meiosis, Mendelian Genetics, Chromosomal Inheritance, Molecular Basis of Inheritance, and Gene Expression

Study Guide - Practice Questions

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