Question 1

Which of the following best explains why sickle cell anemia persists in certain human populations, despite its negative health effects?

Accepted Answer

Individuals with one sickle cell allele (heterozygotes) have increased resistance to malaria, demonstrating natural selection due to selective pressure.

Question 2

A eukaryotic cell is missing its mitochondria. Which process would be most directly affected?

Accepted Answer

ATP production via aerobic cellular respiration

Question 3

Which of the following best describes the difference between prokaryotic and eukaryotic cells?

Accepted Answer

Eukaryotic cells have a nucleus containing DNA, while prokaryotic cells have DNA in the nucleoid region.

Question 4

A cell increases in size from a radius of $$2\ \mu m to$$ $$4\ \mu m. $$How does the surface area to volume ratio change, and what is the consequence for cellular function?

Accepted Answer

The ratio decreases, making transport less efficient.

Question 5

Which of the following molecules would most likely require a protein channel to cross the plasma membrane via facilitated diffusion?

Accepted Answer

Glucose

Question 6

Which step of cellular respiration produces the most ATP, and what is the main process responsible?

Accepted Answer

Electron transport chain; chemiosmosis

Question 7

A herbicide inhibits photosystem II in plant cells. What is the most immediate effect on photosynthesis?

Accepted Answer

Oxygen evolution will decrease, and the electron transport chain will be disrupted.

Question 8

Which of the following best describes the role of alternative splicing in eukaryotic gene expression?

Accepted Answer

It increases the number of proteins that can be produced from a single gene.

Question 9

A mutation changes a codon from $$UAC ($$tyrosine) to $$UAA ($$stop codon). What type of mutation is this, and what is the likely effect on the protein?

Accepted Answer

Nonsense mutation; results in a truncated protein

Question 10

Which of the following best explains why pancreatic cells have an abundance of rough endoplasmic reticulum (RER)?

Accepted Answer

They secrete large amounts of digestive enzymes, which are proteins synthesized on the RER.

Question 11

Which of the following is true regarding the difference between active and passive transport across the plasma membrane?

Accepted Answer

Active transport requires energy (often ATP) to move molecules against their concentration gradient.

Question 12

Which of the following best describes the function of DNA polymerase during DNA replication?

Accepted Answer

It adds nucleotides to the growing DNA strand in the 5’ to 3’ direction.

Question 13

A scientist uses gel electrophoresis to analyze DNA samples. What property of DNA allows this technique to separate DNA fragments?

Accepted Answer

DNA fragments are separated based on their size and charge.

Question 14

Which of the following best describes the role of actin and microtubules during cell division?

Accepted Answer

Microtubules form the mitotic spindle, and actin forms the contractile ring during cytokinesis.

Question 15

Which of the following is an example of feedback inhibition in a metabolic pathway?

Accepted Answer

The end product of a pathway binds to an enzyme early in the pathway, decreasing its activity.

Question 16

Which of the following best describes the difference between homologous chromosomes and sister chromatids?

Accepted Answer

Homologous chromosomes are similar but not identical, each inherited from a different parent; sister chromatids are identical copies formed during DNA replication.

Question 17

A researcher is studying a gene with two alleles, $$A ($$dominant) and $$a ($$recessive). If two heterozygous individuals ($$Aa) $$are crossed, what is the expected phenotypic ratio in the offspring?

Accepted Answer

$$3:1 ($$dominant:recessive)

Question 18

Which of the following best describes the purpose of a control group in a scientific experiment?

Accepted Answer

To provide a baseline for comparison, isolating the effect of the independent variable.

Question 19

Which of the following is an example of codominance in genetics?

Accepted Answer

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

Question 20

Which of the following best describes the role of restriction enzymes in molecular biology?

Accepted Answer

They cut DNA at specific sequences, allowing for DNA analysis and cloning.

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