the correct answer is d heterozygous traits contain one dominant and one recessive form of the gene which of the following is true of homozygous trait

HESI A2

Biology HESI A2 Practice Test

1. Which of the following is true of homozygous traits?

A. They are haploid
B. They are denoted AA
C. They are denoted aa
D. They are denoted Aa

Correct answer: B

Rationale: Homozygous traits have two identical forms of the gene, either both dominant (AA) or both recessive (aa). Therefore, choices B and C are true for homozygous traits. Choice A is incorrect because being haploid refers to having a single set of chromosomes, not necessarily homozygous traits. Choice D is incorrect as homozygous traits have identical alleles, so they are not denoted as Aa.

2. As cattle graze, cattle egrets consume the insects they stir up. This is an example of ___________.

A. Mutualism
B. Parasitism
C. Commensalism
D. Competition

Correct answer: C

Rationale: Commensalism is a relationship between two species in which one benefits without affecting the other species. In this scenario, the cattle egrets benefit from the insects stirred up by cattle while the cattle are not significantly impacted by the presence of the egrets. The egrets obtain food easily, and the cattle are neither harmed nor helped by the egrets' presence, making it an example of commensalism. Mutualism involves both species benefiting, parasitism involves one species benefiting at the expense of the other, and competition involves both species being negatively affected by their interactions, none of which apply to the relationship between cattle and cattle egrets in this context.

3. Physical factors such as temperature and pH can alter enzyme activity because they have an effect on the enzyme's ___________.

A. acidity
B. shape
C. chemistry
D. substrate

Correct answer: B

Rationale: Physical factors such as temperature and pH can alter enzyme activity by affecting the enzyme's shape. Enzymes rely on their specific shapes to function properly and catalyze reactions. Any changes in temperature or pH can disrupt these shapes, causing the enzyme to become denatured and lose its functionality. Therefore, alterations in temperature and pH can impact enzyme activity by directly affecting their shapes. Choices A, C, and D are incorrect because while pH can affect acidity and chemical properties of the enzyme, and temperature can influence the enzyme-substrate interaction, the primary reason for enzyme activity alteration due to temperature and pH is the change in the enzyme's shape.

4. Which statement is untrue?

A. RNA is single-stranded.
B. RNA contains uracil.
C. DNA codes for proteins.
D. DNA cannot be altered.

Correct answer: D

Rationale: DNA can be altered through various processes such as mutations, genetic engineering, and epigenetic modifications. Changes in DNA can occur naturally or through external influences, leading to variations in the genetic code. Therefore, the statement that DNA cannot be altered is untrue. Choices A, B, and C are true statements. RNA is indeed single-stranded, RNA contains uracil instead of thymine, and DNA serves as a template for protein synthesis.

5. What is the main function of the ribosomes in the cell?

A. DNA Replication
B. Protein Synthesis
C. Lipid Breakdown
D. Cell Division

Correct answer: B

Rationale: The correct answer is B: Protein Synthesis. Ribosomes are cellular organelles responsible for synthesizing proteins. This process is crucial for various cellular functions. Choice A, DNA Replication, is incorrect as ribosomes are not involved in this process. Choice C, Lipid Breakdown, is also incorrect as ribosomes do not play a role in lipid metabolism. Choice D, Cell Division, is incorrect as ribosomes are not directly involved in the process of cell division.