Question

Scientists find a gene $P$ that helps human peripheral neurons to sense temperature less than 13°C and induce a physiological signal of avoidance. This gene is present in almost all vertebrates. Considering that gene $P$ has role only in detection of low temperature, the correct statement(s) is (are) ___.

• A. Gene $P$ is beneficial for humans as it warns the body against low temperature.
• B. Loss-of-function mutant of gene $P$ most likely survive in ambient temperature in laboratory conditions.
• C. Gene $P$ may be lost in fish that live in cold waters.
• D. Gene $P$ must be hyperactivated in fish that live in cold water.

Answer 1

Answer: (A), (B), (C)

A, B, C

Answer 2

The question describes a gene P that helps human peripheral neurons sense temperatures less than 13°C and induces a physiological signal of avoidance. Its role is only in the detection of low temperature, and it is present in almost all vertebrates.

Let's analyze each statement:

(A) Gene P is beneficial for humans as it warns the body against low temperature.

Temperatures below 13°C can be harmful to humans, leading to conditions like hypothermia or frostbite. A gene that warns the body and induces an avoidance signal (e.g., pain, discomfort leading to withdrawal) against such low temperatures is clearly beneficial for preventing injury and promoting survival. This statement is correct.

(B) Loss-of-function mutant of gene P most likely survive in ambient temperature in laboratory conditions.

A loss-of-function mutant means gene P is non-functional. Ambient temperature in a laboratory is typically around 20-25°C, which is well above 13°C. Since gene P's function is only to detect temperatures less than 13°C, it would not be active at ambient temperatures. Therefore, its absence or non-functionality would not affect survival in these conditions. This statement is correct.

(C) Gene P may be lost in fish that live in cold waters.

Fish that live in consistently cold waters (e.g., polar fish, deep-sea fish) are adapted to thrive at temperatures well below 13°C. If gene P's function is to induce an avoidance signal for temperatures below 13°C, then in an environment where the temperature is always below 13°C, this gene would be constantly active, signaling avoidance. This would be maladaptive for an organism that lives and thrives in such conditions. Through natural selection, genes that are no longer beneficial or become detrimental in a specific environment can be lost or modified over evolutionary time. Therefore, it is plausible that gene P could be lost in such fish. This statement is correct.

(D) Gene P must be hyperactivated in fish that live in cold water.

Hyperactivation of gene P would mean an increased sensitivity or response to low temperatures, leading to a stronger or more frequent avoidance signal. As explained in (C), for fish that live in cold water, a constant avoidance signal would be counterproductive and detrimental to their survival and adaptation. They need to tolerate and thrive in cold, not constantly avoid it. Therefore, hyperactivation of gene P would be disadvantageous. This statement is incorrect.

Based on the analysis, statements (A), (B), and (C) are correct.