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Q: a. In which sex, XY males or XX females, would the Sxl protein bind to the msl-2 mRNA? b. As…
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Explain how X-chromosome inactivation may affect the
The inactivation center called XCI is responsible for the inactivation of X-chromosomes. This center has an important role in the activation process.
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- Discuss the genetic determination of sex and the inheritance of X-linked genes in mammals.Describe the molecular process of X-chromosome inactivation.This description should include the three phases of inactivationand the role of the Xic. Explain what happens to the X chromosomes during embryogenesis, in adult somatic cells, and duringoogenesis.Briefly describe the molecular processes that cause one X chromosome in each female cell to be active and the other X chromosome to be inactivated.
- Discuss how and why x - linked inactivation alters the genome of a female.You are interested in the expression of regions of the X chromosome at different times in human fetal development. You hypothesize that large regions of the X chromosomes will be expressed at times when parts of the reproductive organs are developing. What structural and chemical characteristics of the X chromosome might you look at over time to determine when expression of genes on the X chromosome is enhanced or repressed?Why does X inactivation occur in female mammals?
- Outline the molecular mechanism of sex determination in Drosophila and mammals.Figure 19.25 shows that the Sxl protein binds to the mRNA of the msl-2 gene, inhibiting translation of the mRNA’s proper reading frame. The MSL-2 protein is a transcription factor that binds to the X chromosome in XY males to double the level of X-linked gene transcription, thus equalizing X-linked gene expression in XY males and XX females. a. In which sex, XY males or XX females, would the Sxl protein bind to the msl-2 mRNA? b. As discussed in Problem 35, some Sxl alleles are lethal to females and others are lethal to males. Is the function of Sxl in regulating the synthesis of Msl-2 protein sufficient to explain the sex-specific lethality caused by both kinds of alleles? c. Predict the effect of loss-of-function mutations in msl-2 on male and female fertility and viability.Describe when X-chromosome inactivation occurs and how thisleads to phenotypic results at the organism level. In your answer,you should explain why XCI causes results such as variegated coatpatterns in mammals. Why do two different calico cats have theirpatches of orange and black fur in different places? Explainwhether or not a variegated coat pattern due to XCI could occur inmarsupials.
- Human females who are heterozygous for an X-linked recessive allele sometimes exhibit mild expression of the trait. However, such mild expression of X-linked traits in females who are heterozygous for Xlinked alleles is not seen in Drosophila. What might cause this difference in the expression of X-linked genes between human females and female Drosophila? (Hint: In Drosophila, dosage compensation is accomplished by doubling the activity of genes on the X chromosome of males.)Which findings support the fact that the presence of the Y- chromosome rather than the lack of a second X-chromosome determines the development of maleness in mammals? A transgenic mouse with two X-chromosomes and the SRY gene from the Y-chromosome develops male sex organs. A human with an XXXY genotype (Klinefelter syndrome) is phenotypically male. A human with an XO genotype (Turner syndrome) is phenotypically female. a and b, but not c a, b, and cWhich is a FALSE statement about X inactivation in mammalian females? O Females that are heterozygous for an X-linked gene have patches of cells that express one allele and patches of cells that express the other. O Xinactivation is random as to which X is inactivated and takes place early in embryonic development Inactivation is initiated by expression of the Xist gene on the X chromosome that will remain active. Once an X chromosome first becomes inactivated in a cell, that same X will remain inactivated in somatic cells that are descendants of this cell. DOOO