the fur color in a population of dogs is controlled by two alleles black b and tan b the black allele exhibits complete dominance if the phenotype of

HESI A2

Biology HESI A2 Practice Test

1. The fur color in a population of dogs is controlled by two alleles: black (B) and tan (b). The black allele exhibits complete dominance. If the phenotype of the dog is tan fur, what is its genotype?

A. BB
B. Bb
C. bb
D. Not enough information

Correct answer: C

Rationale: The correct answer is C: "bb." Since tan fur is the recessive trait controlled by the allele 'b,' the only possible genotype for a dog with tan fur is 'bb.' If a dog had the genotype 'BB' or 'Bb,' the dominant trait (black fur) would be expressed, not tan fur. Choice D, 'Not enough information,' is incorrect because based on the information provided, we can deduce the genotype of a dog with tan fur.

2. In an example of a male with hemophilia and a female carrier, what ratio of the offspring are predicted neither to carry nor to manifest the disease?

A. 0 females : 1 male
B. 1 female : 1 male
C. 1 female : 0 males
D. 2 females : 1 male

Correct answer: D

Rationale: In this scenario, the male offspring will inherit the Y chromosome from the father and the X chromosome from the carrier mother. As a result, they will not have the hemophilia gene. The female offspring will inherit one X chromosome from the mother, which does not carry the hemophilia gene, and one X chromosome from the father, which does not exist due to the Y chromosome. Therefore, all female offspring will not carry or manifest hemophilia, resulting in a ratio of 2 females to 1 male. Choice A is incorrect because it does not account for the female offspring. Choices B and C are incorrect as they do not reflect the correct ratio based on the inheritance pattern of hemophilia.

3. RNA is made from DNA through a process called ___________.

A. transcription
B. synthesis
C. translation
D. replication

Correct answer: A

Rationale: RNA is made from DNA through a process called transcription. During transcription, an enzyme called RNA polymerase reads the DNA template and synthesizes a complementary RNA molecule. This process is essential for gene expression and allows the information encoded in DNA to be converted into functional RNA molecules. Choice B, 'synthesis,' is incorrect as it is a general term and does not specifically describe the process of RNA formation from DNA. Choice C, 'translation,' is incorrect as it refers to the process where the mRNA is used to assemble amino acids during protein synthesis, not the conversion of DNA to RNA. Choice D, 'replication,' is incorrect as it is the process of making an identical copy of DNA, not converting DNA into RNA.

4. If a hard-boiled egg is placed in a beaker of saltwater, what will happen to the egg?

A. Expand because water will move into the egg
B. Shrivel because water will leave the egg
C. Remain the same
D. None of the above

Correct answer: B

Rationale: The correct answer is B. When a hard-boiled egg is placed in a beaker of saltwater, the egg will shrivel because water will leave the egg through osmosis. Osmosis is the movement of water from an area of lower solute concentration to an area of higher solute concentration, in this case, from the egg into the saltwater. The higher concentration of solute in the saltwater causes water to move out of the egg, leading to the egg shrinking or shriveling. Choices A, C, and D are incorrect because the egg will not expand, remain the same, or have an outcome different from shriveling when placed in a beaker of saltwater.

5. Which structure controls the passage of substances into and out of the cell?

A. Vacuole
B. Cell Membrane
C. Nuclear Membrane
D. Cytoplasm

Correct answer: B

Rationale: The correct answer is the Cell Membrane. The cell membrane acts as a barrier that controls the passage of substances into and out of the cell. It is selectively permeable, allowing only certain molecules to pass through. Vacuole (Choice A), Nuclear Membrane (Choice C), and Cytoplasm (Choice D) do not primarily regulate the passage of substances in and out of the cell. Vacuoles are responsible for storage, the nuclear membrane surrounds the nucleus providing protection, and the cytoplasm is the fluid where organelles are suspended.