Nokea
In a plant in which fuzzy leaves (F) are dominant over smooth leaves (f), which of the following crosses will reproduce only offspring with smooth leaves?
- A. FF by ff
- B. ff by ff
- C. Ff by Ff
- D. FF by FF
Correct Answer: B
Rationale: The correct answer is B: 'ff by ff.' When a plant with fuzzy leaves (Ff) is crossed with another plant with smooth leaves (ff), all the offspring will inherit one smooth leaf allele from the smooth-leaved parent, resulting in only smooth leaves. The genotype of the offspring will be ff, leading to the expression of smooth leaves. This cross ensures that both alleles for leaf texture are the recessive smooth allele (f), resulting in all offspring having smooth leaves.
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Which of the following is a component of the integumentary system that secretes pheromones?
- A. Apocrine glands
- B. Seminiferous tubules
- C. Dermal papilla
- D. Fossa ovalis
Correct Answer: A
Rationale: The correct answer is Apocrine glands (Choice A). Apocrine glands are a component of the integumentary system that secretes pheromones. These glands are responsible for producing a type of sweat that contains pheromones, which are chemical signals used for communication between individuals of the same species. Seminiferous tubules (Choice B) are part of the male reproductive system, responsible for producing sperm. Dermal papilla (Choice C) is involved in hair growth and nourishment. Fossa ovalis (Choice D) is a depression in the interatrial septum of the heart. Therefore, the correct choice related to the integumentary system and pheromone secretion is Apocrine glands.
From which region of the intestine does the vermiform appendix extend, known as which of the following?
- A. Ischium
- B. Cecum
- C. Rectum
- D. Jejunum
Correct Answer: B
Rationale: The correct answer is B, Cecum. The vermiform appendix, a small tube-like structure, extends from the cecum, located in the lower right quadrant of the abdomen. Knowing the anatomical relationships among different intestinal parts is essential for identifying the appendix's origin.
What is the function of the myelin sheath for a nerve cell?
- A. Sensory perception
- B. Insulation
- C. Nutrition
- D. Regeneration
Correct Answer: B
Rationale: The myelin sheath functions as an insulator for nerve cells, enabling the rapid transmission of electrical impulses along the nerve fiber. This insulation is essential for maintaining the speed and efficiency of nerve signal conduction. Sensory perception involves detecting sensory stimuli, nutrition involves the supply of nutrients, and regeneration is the process of regrowth or repair, which are distinct functions from what the myelin sheath provides.
After infecting host cells, how does the AIDS virus, which contains RNA, insert viral DNA into the host T-cell?
- A. Receptor proteins located on the surface of the virus
- B. Reverse transcriptase, an enzyme encoded by the virus
- C. The phospholipids found on the envelope of the virus
- D. The protein that makes up the capsid of the virus
Correct Answer: B
Rationale: Reverse transcriptase is an essential enzyme unique to retroviruses like the AIDS virus. It catalyzes the conversion of viral RNA into DNA through a process known as reverse transcription. The newly formed viral DNA is then integrated into the host cell's genome, enabling the virus to replicate and establish a persistent infection within the host.
In a study, two processes, process A and process B, were found to be correlated. Which of the following statements is true regarding these processes?
- A. The study cannot determine if processes A and B have a negative relationship.
- B. The study suggests that process A causes process B.
- C. The study cannot determine if processes A and B have a positive relationship.
- D. The study does not establish a causal relationship between process A and process B.
Correct Answer: D
Rationale: When two processes are correlated, it means changes in one process are linked to changes in the other. However, correlation does not imply causation. Therefore, the study does not establish a causal relationship between process A and process B solely based on correlation. Correlation does not provide information on the direction or cause of the relationship between the processes. It only indicates that the processes vary together in a predictable manner. Hence, option D is correct as the study cannot infer causation from correlation alone.