1.Yau study two rat strains, \"Rose and \"Basil\": both strains show high inci o

Question

1.Yau study two rat strains, "Rose and "Basil": both strains show high inci of abarted fetuses if crossed with normal rats. "Rose" was exposed to X-irradiation while she was an embryo,"Basil" was treated with the reagent found in herbicide tormula during embryogenesis. Below is the data you collected on the aborted fetuses: Mother Rose Busil Sex of aborted fetuses Female Furale and rriale Karyotype of aborted fetuses No Barr hodies All X chrorrioso forr Burr budics Notc: Below questiorrs are nut about whot defert theX rayfuto treotment has cusd; thic questions ore abour whot mkes rhe offspring die or not die. Explain whry AJ All of Rose's daughters die B) All of Rose's sons survive C) All ot Basil's oftspring die

Explanation / Answer

A.

Barr bodies present in the female. Barr body is compressed X chromosome out of two present in the female. Barr body plays an important role in the somatic cells but not in the gamete cells. The karyotype of aborted fetuses show no Barr body in the female comes from rose. This means that the one X chromosome out of two get damaged and this is the reason that all the Rose’s daughters die.

B.

A male usually does not contain the Barr bodies. So, the survival of male is not affected by the absence of the Barr body.

C.

All the Basil’s offspring die because in case of female there are two X chromosomes and both becomes Barr body whereas in normal case only one X chromosome converts to the Barr body. In case of the males, there is only one X chromosome and males do not contain the Barr body. A single X chromosome in the male is also converted to the Barr body.

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