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. What are plasma membranes mostly made of?

A. Proteins
B. Carbohydrates
C. Lipids
D. Nucleotides

Correct answer: C

Rationale: The correct answer is C: Lipids. Plasma membranes are primarily composed of lipids, specifically phospholipids, which form a lipid bilayer. While proteins are also an essential component of plasma membranes, they are not the primary constituent. Carbohydrates are present on the outer surface of the membrane but are not the main structural component. Nucleotides are the building blocks of nucleic acids like DNA and RNA and are not the main constituents of plasma membranes.

3. Why do cells need to use exocytosis?

A. To obtain energy
B. To defend against invaders
C. To remove waste products
D. To undergo division

Correct answer: C

Rationale: Cells need to use exocytosis to remove waste products from the cell. Exocytosis is a process where cells release molecules or substances outside the cell by fusing vesicles with the cell membrane. This process is crucial for maintaining cellular homeostasis by efficiently eliminating waste materials. Choices A, B, and D are incorrect because exocytosis is specifically involved in the expulsion of molecules, not for obtaining energy, defending against invaders, or cell division.

4. What organelle pushes water out of the cell?

A. Lysosomes
B. Vacuoles (contractile)
C. Mitochondria
D. Nucleus

Correct answer: B

Rationale: The correct answer is B: Vacuoles (contractile). Vacuoles (contractile) are responsible for expelling excess water out of the cell. Lysosomes are involved in the digestion and removal of waste materials, mitochondria are the powerhouse of the cell involved in energy production, and the nucleus contains the cell's genetic material but does not play a role in pushing water out of the cell.

5. Prokaryotic cells:

A. Have a nucleus
B. Have a capsule
C. Have membrane-bound organelles
D. Cannot move on their own

Correct answer: B

Rationale: Prokaryotic cells do not have a nucleus or membrane-bound organelles. One characteristic feature of prokaryotic cells is the presence of a capsule, which is a protective layer outside the cell wall. This capsule helps the prokaryotic cell adhere to surfaces, evade the host immune system, and protect against desiccation. Choice A is incorrect because prokaryotic cells lack a nucleus. Choice C is incorrect as prokaryotic cells do not have membrane-bound organelles. Choice D is incorrect as prokaryotic cells can move using structures like flagella or pili.