A gene for a certain type of insensitivity to pain, an analgesia, is on an autos

Question

A gene for a certain type of insensitivity to pain, an analgesia, is on an autosome. Individuals with this analgesia are aware of stimuli but do not perceive harmful stimuli as pain. Several couples, in each of which one parent has a normal pain response and the other is analgesic, all have some offspring that are analgesic and others with a normal response to pain. a. On the basis of the observation above, can you conclude that the analgesic phenotype is determined by a recessive allele of this autosomal gene? Explain your answer, using appropriate symbols for which you provide a legend. b. Other couples, in which both parents have a normal pain response, all have some offspring that are normal and others that are analgesic. Does this observation change your answer to the question above? Explain. c. Determine the possible phenotypes of offspring from a couple in which both parents are analgesic.

Explanation / Answer

a. The analgesic phenotype is on an autosome, that is a nonsex chromosome. If one copy of the gene ispresent in the parent, they would be carriers. But they may not express the trait, as the gene is recessive. Hence the offsprings show both analgesic and normal characterstics.

b.The observation that both parents having normal pain response, have offsprings where few are normal and few are analgesic is true. So there is no change in the above answer(a). This is because, the parents may not show any analgesic trait but carry the recessive allele, which may be passed on to the offsprings. If both the parents are carriers, then the analgesic trait(recessive autosomal) will be shown by some offsprings.

c.If both parents are analgesic, then the offsprings would be analgesic only , as each of the parents have both the changed genes , meaning two copies of abnormal gene is present in both the parents.

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