Question 1

Which of the following best describes the difference between paracrine signaling and endocrine signaling in multicellular organisms?

Accepted Answer

Paracrine signaling involves local mediators affecting nearby cells, while endocrine signaling involves hormones traveling through the bloodstream to distant target cells.

Question 2

A researcher discovers a mutation that prevents a cell from producing cAMP in response to a signal. Which step in the signaling pathway is most likely disrupted?

Accepted Answer

The activation of adenylyl cyclase by a G protein.

Question 3

Which of the following statements about receptor tyrosine kinases (RTKs) is correct?

Accepted Answer

RTKs are activated by dimerization and autophosphorylation after ligand binding.

Question 4

During cell division, which cytoskeletal component is primarily responsible for the formation of the cleavage furrow in animal cells?

Accepted Answer

Microfilaments (actin filaments)

Question 5

A human somatic cell in G2 phase contains 46 chromosomes. How many chromatids are present in this cell?

Accepted Answer

$$92$$

Question 6

Which checkpoint in the cell cycle is primarily responsible for ensuring that all DNA has been accurately replicated before mitosis begins?

Accepted Answer

G2 checkpoint

Question 7

Which of the following events is unique to meiosis I and does NOT occur in mitosis?

Accepted Answer

Pairing and separation of homologous chromosomes

Question 8

Independent assortment of chromosomes occurs during which phase of meiosis?

Accepted Answer

Metaphase I

Question 9

A plant with genotype $$YyRr ($$yellow, round seeds) is crossed with a plant with genotype $$yyrr ($$green, wrinkled seeds). What is the expected phenotypic ratio among the offspring?

Accepted Answer

$$1:1:1:1 ($$yellow round : yellow wrinkled : green round : green wrinkled)

Question 10

In Mendel’s monohybrid cross between true-breeding purple-flowered plants and true-breeding white-flowered plants, all F1 offspring had purple flowers. What does this demonstrate about the purple flower allele?

Accepted Answer

It is dominant to the white flower allele.

Question 11

A cell is exposed to a signal molecule, but does not respond. Which of the following best explains why?

Accepted Answer

The cell lacks the specific receptor for the signal molecule.

Question 12

Which of the following best describes the role of a phosphatase in cell signaling?

Accepted Answer

It removes phosphate groups from proteins, often deactivating them.

Question 13

In the nematode C. elegans, apoptosis is essential for normal development. Which of the following is a key feature of apoptosis in this organism?

Accepted Answer

Programmed cell death is controlled by specific genes and results in the orderly dismantling of cellular components.

Question 14

A diploid organism has $$2n = 16$$ chromosomes. After meiosis II, how many chromosomes are present in each gamete?

Accepted Answer

$$8$$

Question 15

Which of the following best explains why cancer cells can divide uncontrollably?

Accepted Answer

They bypass or ignore cell cycle checkpoints that normally prevent damaged cells from dividing.

Question 16

A testcross is performed between a plant with an unknown genotype for a dominant trait and a homozygous recessive plant. If the unknown plant is heterozygous, what phenotypic ratio is expected among the offspring?

Accepted Answer

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

Question 17

Which of the following is true about homologous chromosomes?

Accepted Answer

They carry the same genes but may have different alleles.

Question 18

If two heterozygous individuals ($$Aa) $$are crossed, what is the expected genotypic ratio among their offspring?

Accepted Answer

$$1:2:1 (AA$$:Aa:aa)

Question 19

Which of the following best describes the law of independent assortment?

Accepted Answer

Alleles of different genes are distributed independently of one another during gamete formation.

Question 20

A cell has just completed DNA replication. If the original cell had $$n$$ chromosomes, how many chromatids does it have now?

Accepted Answer

$$2n$$

Cell Communication, Cell Cycle, Meiosis, and Mendelian Genetics: Study Guide (Chapters 11-14)

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