Nursing Elites

1. Two mice are both heterozygous for two traits: white fur (Ww) and short fur (Ss). Their offspring are most likely to have which of the following genotypes for these traits?

• A. wwss
• B. WWSS
• C. WwSs
• D. WWSs

Correct answer: C

Rationale: When two mice that are heterozygous for white fur (Ww) and short fur (Ss) mate, they can produce offspring with different combinations of the two traits. The Punnett square for this cross shows that the most likely genotype for the offspring is WwSs. In this case, each offspring receives one allele for white fur (W) and one for short fur (S) from each parent, resulting in a heterozygous genotype for both traits. Choice A (wwss) is incorrect as it represents a homozygous recessive genotype for both traits. Choice B (WWSS) is also incorrect as it represents a homozygous dominant genotype for both traits. Choice D (WWSs) is incorrect as it represents a genotype where one trait is homozygous dominant (W) and the other is heterozygous (S), which is not the most likely outcome based on the given parental genotypes.

2. Which type of epithelium lines the inner surface of the oral cavity, providing a barrier against external insults?

• A. Simple squamous epithelium
• B. Stratified squamous epithelium
• C. Simple columnar epithelium
• D. Pseudostratified columnar epithelium

Correct answer: B

Rationale: The oral cavity is constantly exposed to mechanical stress and potential injury from food particles and other external factors. To protect against these insults, a strong and resilient epithelium is needed. Stratified squamous epithelium is the best choice for lining the oral cavity due to its multiple layers of cells. This type of epithelium provides a robust barrier that can withstand abrasion and protect the underlying tissues. Simple squamous epithelium (choice A) is too thin and not suitable for a protective function. Simple columnar epithelium (choice C) is more suited for absorption and secretion functions, not protection against mechanical stress. Pseudostratified columnar epithelium (choice D) is found in respiratory passages and functions in mucociliary clearance, not in providing a protective barrier against external insults in the oral cavity.

3. Which part of the neuron receives incoming signals from other neurons and conducts them toward the cell body?

• A. Axon
• B. Dendrite
• C. Synapse
• D. Myelin sheath

Correct answer: B

Rationale: The dendrites are the part of the neuron that receive incoming signals from other neurons and conduct them toward the cell body. They play a crucial role in integrating signals received from other neurons. The dendrites are covered in synapses, which are the junctions where communication between neurons occurs. The axon, on the other hand, is responsible for transmitting signals away from the cell body. The synapse is the gap between neurons where neurotransmitters are released to facilitate communication. Lastly, the myelin sheath is a fatty layer that insulates and speeds up signal transmission along the axon, helping in the efficient conduction of nerve impulses.

4. In a food chain, which trophic level captures energy from the sun?

• A. Decomposers
• B. Carnivores
• C. Producers
• D. Omnivores

Correct answer: C

Rationale: Producers, such as plants, algae, and some bacteria, are the organisms in a food chain that capture energy from the sun through the process of photosynthesis. They convert sunlight into chemical energy, which is then passed on to other organisms in the food chain. Producers are at the base of the food chain and form the foundation for all other trophic levels to obtain energy. Decomposers (option A) break down organic matter, carnivores (option B) consume other animals, and omnivores (option D) consume both plants and animals, but they do not directly capture energy from the sun.

5. How many chromosomes must a normal human sperm cell contain?

• A. An X chromosome.
• B. A Y chromosome.
• C. 23 chromosomes.
• D. Both an X and Y chromosome.

Correct answer: C

Rationale: A normal human sperm cell contains a total of 23 chromosomes, half the number found in a typical human cell which has 46 chromosomes. This includes 22 autosomes and one sex chromosome, which can be either an X or a Y chromosome. Therefore, the correct answer is that a normal human sperm cell must contain 23 chromosomes. Choices A and B are incorrect because a single sex chromosome alone does not represent the total number of chromosomes in a sperm cell. Choice D is incorrect because a sperm cell carries only one sex chromosome, either X or Y, not both.

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