d. Predict the potential outcome for the embryo of the following mutations/manip
ID: 85795 • Letter: D
Question
d. Predict the potential outcome for the embryo of the following mutations/manipulations. Note, there is not necessarily a known correct answer -this is an exercise to get you to generate hypotheses about why you might expect given your correct understanding of the process. Bicoid gene mutated (non-functional) in mother Extra Bicoid mRNA deposited in anterior end Nanos gene is mutated (non-functional) in mother Bicoid protein is only partially functional (works slower) A mutation occurred that prevented the transport of Nanos mRNA to posterior endExplanation / Answer
1. Biscoid gene mutated in mother: No biscoid mRNA gradient will be formed on anterior side. No biscoid proteins will be formed. As biscoid protein inhibits the translation of caudal RNA at anterior end, it will allow caudal protein to be synthesized in anterior region. Also the hunchback level will be decreased ( as it is actived by biscoid). Overall effect will be the formation of tail on anterior side.
2. Extra biscoid mRNA on anterior side: More inhibition of caudal RNA and activation of hunchback gene. As the presench of hunch back inhibits the development of posterior structure, tail will not be formed.
3. Nanos gene is mutated: Absence of nanos protein on the posterior part plus excess of hunchback protein (as nanos is the inhibitor of hunchback) causes formation of head structures in posterior end.
4. Biscoid protein functions partially: Small levels of biscoid still maintains the gradient, but will not be able to completly inhibit the caudal protein in the anterior side, which may lead to the synthesis of tail structure on anterior side.
5. A mutation occur in transfer of nanos mRNA to posterior side: Nanos protein will be accumulated at the anterior side. It will also repress the expression of hunchback gene in the anterior side, therefore anterior parts (head, thorax) will not be formed and tail structures may form at this site.
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