Question 1

During which specific stage of meiosis does crossing over occur, and why is this process important for sexually reproducing organisms?

Accepted Answer

Crossing over occurs during Prophase I and is important because it creates genetic variation by exchanging DNA between homologous chromosomes.

Question 2

A woman is a carrier for color blindness (an X-linked recessive trait), and her partner has normal vision. What is the probability that their son will be color blind?

Accepted Answer

$$50\%$$

Question 3

Which of the following best explains the Law of Independent Assortment as demonstrated by Mendel's dihybrid crosses?

Accepted Answer

Alleles for different genes separate independently during gamete formation, resulting in new combinations of traits.

Question 4

A cell with a diploid number of $$2n = 8$$ undergoes meiosis. How many chromosomes will each resulting gamete contain?

Accepted Answer

$$4$$

Question 5

Which enzyme is responsible for synthesizing the RNA primer during DNA replication, and why is this primer necessary?

Accepted Answer

Primase; the primer provides a starting point with a free 3' OH group for DNA polymerase to begin DNA synthesis.

Question 6

A mutation changes a codon from $$	ext{UAC} ($$tyrosine) to $$	ext{UAA} in $$the middle of an mRNA sequence. What type of mutation is this, and what is its likely effect on the protein?

Accepted Answer

Nonsense mutation; it introduces a premature stop codon, likely resulting in a truncated, nonfunctional protein.

Question 7

Which of the following best describes the difference between incomplete dominance and codominance?

Accepted Answer

Incomplete dominance results in a blended phenotype, while codominance results in both traits being fully expressed.

Question 8

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

Accepted Answer

Hershey-Chase experiment using viruses and radioactive labeling.

Question 9

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

Accepted Answer

Barr body; it ensures dosage compensation of X-linked genes in females.

Question 10

Which of the following best explains why Okazaki fragments are formed during DNA replication?

Accepted Answer

DNA polymerase can only synthesize DNA in the $$5' \rightarrow 3'$$ direction, so the lagging strand is synthesized discontinuously.

Question 11

A couple, both heterozygous for a gene with complete dominance ($$Pp$$), have a child. What is the probability that the child will display the recessive phenotype?

Accepted Answer

$$25\%$$

Question 12

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

Accepted Answer

Information flows from DNA to RNA to protein.

Question 13

A mutation in the gene encoding hemoglobin causes sickle cell disease. This is an example of which type of inheritance?

Accepted Answer

Codominance, because both normal and sickle hemoglobin are expressed in heterozygotes.

Question 14

Which of the following best describes the function of telomeres in eukaryotic chromosomes?

Accepted Answer

They protect chromosome ends from deterioration and prevent loss of genetic information during replication.

Question 15

A DNA sample contains $$30\%$$ adenine. According to Chargaff's rules, what percentage of guanine does it contain?

Accepted Answer

$$20\%$$

Question 16

Which of the following is a real-world example of polygenic inheritance?

Accepted Answer

Human skin color, which is influenced by multiple genes.

Question 17

During transcription in eukaryotes, which sequence signals the start of gene transcription, and which enzyme binds to it?

Accepted Answer

The promoter (containing the TATA box); RNA polymerase binds to it.

Question 18

A frameshift mutation is generally more severe than a missense mutation because:

Accepted Answer

It alters the reading frame, potentially changing every amino acid downstream of the mutation.

Question 19

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

Accepted Answer

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

Question 20

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

Accepted Answer

Genetic variation among gametes due to random orientation of homologous chromosomes in Metaphase I.

Meiosis, Mendelian Genetics, Chromosomal Inheritance, DNA Structure & Replication, Gene Expression, and Mutations

Study Guide - Practice Questions

Study Guide - Flashcards