what happens during the s phase of the cell cycle

HESI A2

HESI A2 Practice Test Biology

1. What happens during the S phase of the cell cycle?

A. Chromosomes are duplicated.
B. Cell growth occurs.
C. DNA is synthesized.
D. DNA is destroyed.

Correct answer: A

Rationale: During the S phase of the cell cycle, chromosomes are duplicated. This is a critical step in cell division as each chromosome is replicated to ensure that the resulting daughter cells receive an identical set of genetic information. Choices B, C, and D are incorrect because cell growth primarily occurs in the G1 phase, DNA synthesis happens during the S phase, and DNA destruction does not occur during any phase of the cell cycle.

2. Which structure might be described as a core of nucleic acid surrounded by a protein coat?

A. RNA
B. Virus
C. Blue-green alga
D. Saprophyte

Correct answer: B

Rationale: A virus can be described as a core of nucleic acid (either RNA or DNA) surrounded by a protein coat, known as a capsid. This structure distinguishes viruses from other microorganisms such as blue-green algae (Cyanobacteria), fungi known as saprophytes, or individual RNA molecules. Viruses depend on a host cell to replicate and are considered non-living entities due to their inability to carry out metabolic functions independently.

3. How does asexual reproduction differ from sexual reproduction?

A. asexual reproduction results in all cells being identical to the original cell; sexual reproduction results in half of the cells being identical to the original cell
B. asexual reproduction results in two cells that contribute genetic material to daughter cells, resulting in significantly greater variation
C. sexual reproduction involves two cells that contribute genetic material to daughter cells, resulting in significantly greater variation
D. sexual reproduction involves one cell that yields all cells produced to be identical

Correct answer: C

Rationale: Sexual reproduction involves two cells (gametes) that contribute genetic material to daughter cells, resulting in significantly greater genetic variation in the offspring. This genetic variation is essential for evolution and adaptation to environmental changes. In contrast, asexual reproduction involves one cell dividing to produce offspring that are genetically identical to the parent cell. Choice A is incorrect because sexual reproduction does not result in half of the cells being identical to the original cell; it involves two cells contributing genetic material. Choice B is incorrect because asexual reproduction does not result in significantly greater variation; it produces genetically identical offspring. Choice D is incorrect because sexual reproduction involves two cells contributing genetic material, not one cell yielding all identical cells.

4. Which, if any, of the following statements about the biosphere is correct?

A. The biosphere is the part of the Earth that supports life.
B. The biosphere encompasses the entire surface of the Earth.
C. A and B are correct.
D. None of these statements is correct.

Correct answer: A

Rationale: Statement A is correct. The biosphere refers to the part of the Earth where life exists, including the land, water bodies, and atmosphere. It is the zone where living organisms and ecosystems exist. Statement B is incorrect because the biosphere covers various ecosystems on Earth but does not encompass the entire surface of the planet. The biosphere includes regions such as the lithosphere (land), hydrosphere (water bodies), and atmosphere, but not every part of the Earth's surface. Therefore, option C, stating both A and B are correct, is inaccurate. The correct answer is option A, as it accurately defines the biosphere.

5. A cell that does not contain membrane-bound organelles or a defined nucleus would be classified as:

A. eukaryotic
B. embryonic
C. prokaryotic
D. symbiotic

Correct answer: C

Rationale: A cell that does not contain membrane-bound organelles or a defined nucleus is classified as prokaryotic. Prokaryotic cells lack a true nucleus, and their genetic material is typically found in a region called the nucleoid. Examples of prokaryotic organisms include bacteria and archaea. Eukaryotic cells, on the other hand, contain membrane-bound organelles and a true nucleus, distinguishing them from prokaryotic cells. Embryonic and symbiotic classifications are not directly related to the presence of organelles or a nucleus in cells.