Question 1

Which of the following best describes the process and significance of crossing over during meiosis?

Accepted Answer

Crossing over occurs during prophase I of meiosis, where homologous chromosomes exchange genetic material, increasing genetic variation among gametes.

Question 2

A human cell with 46 chromosomes undergoes mitosis. How many chromosomes will each daughter cell have, and why?

Accepted Answer

Each daughter cell will have 46 chromosomes because mitosis produces genetically identical cells.

Question 3

Which of the following scenarios best illustrates incomplete dominance?

Accepted Answer

A cross between a red-flowered and a white-flowered snapdragon produces pink-flowered offspring.

Question 4

A woman who is a carrier for hemophilia (an X-linked recessive disorder) and a normal man have a son. What is the probability that their son will have hemophilia? Use $$X^H$$ for the normal allele and $$X^h$$ for the hemophilia allele.

Accepted Answer

50% chance, because the son inherits his X chromosome from his mother, who is a carrier ($$X^H X^h$$), and his Y chromosome from his father.

Question 5

Which experiment provided the first direct evidence that DNA, and not protein, is the genetic material?

Accepted Answer

The Avery experiment, which showed that only DNA could transform non-pathogenic bacteria into pathogenic forms.

Question 6

If a DNA strand has the sequence $$5'	ext{-}ATTGCATAC\ 3'$$, what is the sequence of its complementary strand?

Accepted Answer

$$3'	ext{-}TAACGTATG\ 5'$$

Question 7

Which of the following best explains the concept of semiconservative replication in DNA?

Accepted Answer

Each new DNA molecule consists of one old (parental) strand and one newly synthesized strand.

Question 8

A couple has a child with Down syndrome. Which chromosomal event most likely led to this condition?

Accepted Answer

Nondisjunction during meiosis, resulting in an extra chromosome 21.

Question 9

Which of the following best describes the function of transfer RNA (tRNA) during protein synthesis?

Accepted Answer

tRNA carries specific amino acids to the ribosome and matches its anticodon to the codon on mRNA.

Question 10

In a dihybrid cross between two pea plants heterozygous for violet flowers (V) and yellow seeds (Y), what is the expected phenotypic ratio among the offspring?

Accepted Answer

9 violet/yellow : 3 violet/green : 3 white/yellow : 1 white/green

Question 11

Which of the following statements about the lac operon in E. coli is correct?

Accepted Answer

The lac operon is turned on in the presence of lactose because lactose binds to the repressor, preventing it from binding to the operator.

Question 12

Which of the following best describes a frameshift mutation and its likely effect on a protein?

Accepted Answer

A frameshift mutation results from the insertion or deletion of nucleotides, altering the reading frame and usually producing a nonfunctional protein.

Question 13

Which of the following is an example of codominance?

Accepted Answer

A person with blood type AB expresses both A and B antigens equally.

Question 14

Which of the following best explains the difference between autosomes and sex chromosomes?

Accepted Answer

Autosomes are chromosomes that do not determine sex, while sex chromosomes (X and Y) determine an individual's sex.

Question 15

Which of the following best describes the process of making recombinant DNA using a plasmid vector?

Accepted Answer

A gene of interest is cut out using a restriction enzyme, inserted into a plasmid cut with the same enzyme, and joined by DNA ligase.

Question 16

Which of the following is a benefit of genetically modified plants to human society?

Accepted Answer

They can be engineered to resist insect pests, reducing the need for chemical pesticides.

Question 17

A mutation changes the codon $$	ext{GAA} to$$ $$	ext{GUA}. $$What type of mutation is this, and what is its likely effect?

Accepted Answer

This is a point mutation (missense), which may result in a different amino acid being incorporated into the protein.

Question 18

Which of the following best describes the difference between prophase of mitosis and prophase I of meiosis?

Accepted Answer

Homologous chromosomes pair and undergo crossing over in prophase I of meiosis, but not in prophase of mitosis.

Question 19

Which of the following best explains why Mendel's use of pea plants was advantageous for studying inheritance?

Accepted Answer

Pea plants have easily distinguishable traits, short generation times, and produce many offspring, allowing for statistical analysis.

Question 20

Which of the following best describes the role of ribosomal RNA (rRNA) in protein synthesis?

Accepted Answer

rRNA combines with proteins to form ribosomes, which are the sites of protein synthesis.

General Biology 101: Cell Division, Genetics, and Molecular Biology Study Guide

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