BICD100 NAME Section # Turin in your answers with your in-lecture final exam on
ID: 214579 • Letter: B
Question
BICD100 NAME Section # Turin in your answers with your in-lecture final exam on Friday, March 23rd 1.You study two rat strains, "Rose" and "Basil": both strains show high incidence of aborted fetuses if crossed with normal rats. "Rose" was exposed to X-irradiation while she was an embryo; "Basi" was treated with the reagent found in herbicide formula during embryogenesis. Below is the data you collected on the aborted fetuses: Mother Sex of aborted fetuses aryotype of aborted fetuses Rose Basil Female Female and male No Barr bodies All X chromosomes form Barr bodies Note: Below questions are not about what defect the X-ray/mutagen treatment has caused; the questions are about what makes the offspring die or not die. Explain why A) All of Rose's daughters die B) All of Rose's sons survive C) All of Basil's offspring dieExplanation / Answer
A. All of Rose daughter's die because presence of one barr body is essential in females and rose daughters are not having any barr body. The barr body inactivated extra X chromosomes to keep the dosage of genetic products equal. This is called as dosage compensation. Females shut off one of their X chromosomes during embryonic development.
B. All of Ross's sons survive because they don't have a Barr body. The males have only one X chromosome and so they do not possess a Barr body. They don't require dosage compensation due to presence of only one X chromosome.
C. All of Basils offsprings die because every X chromosome had a Barr body. The inactivated X chromosomes are called barr body. Thus, if all X chromosomes are forming the Barr bodies, all X chromosomes are inactivated and no genes will expresses. So, all offsprings will die.
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