AT&T; LTE 12:16 AM ( 0 2196 [ O blackboard.jhu.edu QUESTION 5 2 points Save Answ
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AT&T; LTE 12:16 AM ( 0 2196 [ O blackboard.jhu.edu QUESTION 5 2 points Save Answe The female pattern of splicing is initiated during early development in response to mechanism that computes" the ratio of X chromosomes to autosomes (i.e., the X A ratio). If X:A is equal to 2:2 or 3:3, sex- lethal is transcribed from an alternative promoter (not shown) and the resulting transcript is always spliced in the female pattern resulting in expression of active Sxl protein. When X A equals 1:2 or 1:3, the alternative promoter is not used frequently enough and the cascade is not engaged. When X:A equals 2:3 (for example in XXY triploid animals), mosaic animals are formed in which numerous sectors develop in the female pattern right alongside sectors that develop in the male pattern. Please explain the key elements in the cascade that make its output appear as an all-or none switch that becomes irreversible after it is initially engaged by the X:A computer Path p Words 0 QUESTION 6 1 points Save Answe Twin studies have been used to study the phenotype of "takingExplanation / Answer
The promoters of the Sxl (sex lethal) gene are: Sxlpm and Sxlpe. The regulation of promoters is achieved by pausing of RNA polymerase II in promoter proximal regions earlier to initiation. It is observed in large fraction of gene under developmental control of Drosophila embryo. This pausing mechanism is also associated with regulation of alternative splicing.
Alternative splicing of tra gene is affected by the product of Sxl gene. If the X-chromosome and the autosomes ratio 1:2, then Sxl gene encodes the splicing-factors, that are female specific, and these factors made the alternative splicing of tra gene in a female-specific manner.
The female-specific factors of tra gene interact with tra Tra2 splicing factor to cause the doublesex pre-mRNA to be spliced in a female-specific manner. If the doublesex transcript is not acted on in this way, it will be processed in a “default” manner to make the male-specific message.
Tra-protein complexes made the occurrence of development in a specific manner. For example, if the tra-protein complex and tra-2 are both present, then the dsx transcript is spliced and processed in a female-specific manner. Thus, these processed proteins activate other female development genes and represses the expression of male specific genes.
The female-specific dsx proteins activate the expression of gene that encodes the yolk proteins and yolk development. And also activate other female development genes and represses the expression of male specific genes.
The Ratios of X chromosomes to autosomes in different sexual phenotypes in Drosophila melanogaster are as follows:
Therefore,
If the X: A ratio is 2:3, then the sex of the progeny will be Intersex or hermaphrodites, not a male nor a female.
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