1> Hemophilia is an X-linked trait. Talmud, an ancient book of Jewish civil and
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1> Hemophilia is an X-linked trait. Talmud, an ancient book of Jewish civil and religious laws, states that if a woman bears two ans who die of bleeding ater circumcision, any additional sons that she has should not be The eised. Furthermore, the Talmud states that the sons of her sisters must not be circumcised, whereas the sons of her brothers should. Is this religious law consistent with sound genetic I principles? lyes or no ] And explain nciples? I yes or no ] And explain A geneticist discovers a male mouse with greatly enlarged testes in his laboratory colony He suspects that this trait results from a new mutation that is either Y-linked or autosomal dominant. How could he determine whether the trait is autosomal dominant or Y-linked? Design a genetic cross experiment to prove it.Explanation / Answer
Answer 1: Yes.
If the woman has a hemophilic son, then she (mother) is a carrier. As a result, any of her sons have a 50% chance of showing hemophilia. Now, her sisters can be carriers also. Besides, her brothers, if they do not have hemophilia themselves, they cannot be carriers (as they survived through circumcision, they most likely do not have hemophilia). Therefore there is no risk of transmitting the hemophilia gene to their children.
Answer 2: Here the trait involves the testes( given), it will never be expressed in females whether it is autosomal dominant or Y-linked. For determination, the geneticist should cross a male having the enlarged testes to a female (no such family history of this trait). If the experimental gene of interest is Y-linked, then all the male progeny should have enlarged testes because they all would inherit their Y chromosome from their father. On the other hand, if the trait is autosomal dominant and the affected male is heterozygous, then 50% of the male progeny should have enlarged testes only. Moreover, if the trait is Y-linked then it can never be obtained from a female. To check these conditions, mating of a male with enlarged testes to a normal female should be done. Then the daughters of this cross should be mate to normal males. Now, if enlarged testes result from an autosomal dominant trait that is only expressed in males, 50% of the daughters will be carriers and the gene will pass through them for the trait to 50% of their male offspring with enlarged testes. If it is Y-linked, then females cannot be carriers and none of the male offspring of the daughters will have enlarged testes.
As testes are traits for males, enlarged testes could either be an autosomal dominant trait (sex limited) or a Y-linked trait. Now, considering that the male mouse with enlarged testes is fertile and mating it with a normal female. If the trait is autosomal dominant and the parental male is heterozygous, only 50% the male progeny will show enlarged testes. If the trait is Y-linked, all the male progeny will show enlarged testes. From both this results from this first cross will not be conclusive in this case. If all the male progeny show the trait, it still may be autosomal dominant if the parental male generation was homozygous. On the other hand, if some of the male progeny only express the trait, there is a possibility that the trait is Y-linked but incompletely penetrant. So, in either case, more conclusive experimental evidence is needed. To set the genetic cross, first mate the female progeny, i.e F1females with the normal males. Now, if the trait is autosomal dominant, some of the male F2 offsprings will show enlarged testes. It can be a proof that the trait can be obtained from a female. Whereas, if the trait is Y-linked, then all the male F2 off springs will have normal testes, as their normal father.
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