If the concentration of the Pu
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Correct answers
1.If the concentration of the Pumilio proteinis uniform throughout the drosophila egg cytoplasm, then how doesit inhibit the production of the Hunchback protein at the posteriorend but not the anterior end of the embryo?
D. The protein Pumilio inhibits transcriptionof the hunchback mRNA only in the presence of Nanos, which ispresent in a decreasing gradient from posterior to anterior.
pumilio is a Drosophila gene which expressed maternally andthere is uniformly dispersed throughout the embryo. Pumilio isrequired for embryonic development. During early embryonicdevelopment when the genome is transcriptionally silent maternallyderived mRNA transcripts regulates the expression patterns of theembryo. During this stage, mRNA encoding Hunchback are regulated byPumilio. Hunchback mRNA is distributed throughout the embryo butthe protein must be restricted to the embryonic anterior. Nanosspatially restricts Hunchback expression by originating from theposterior pole and thus opposing the Hunchback gradient.
for repression of Hunchback there are Nanos response elements(NREs) whuch are the RNA sequences located in the 3′ untranslatedregion (3′ UTR) of Hunchback mRNA, These NREs are the binding sitesfor Pumilio. A trimeric Nanos-Pumilio-NRE complex is formed whenNanos partners with Pumilio on the NREs, This complax in turnrepresses Hunchback .
2. Draw the structures of the four DNA bases inyour scrapbook and state the position of the substitutions on thecentral ring structure. Name the central ring structure.
A. A: 6-aminopurine; G: 2-amino6-hydroxypurine; C: 2-hydroxy 4-aminopyrimidine; T:2,4-dihydroxy-5-methylpyrimidine
3. What is a chi sequence?
C. 5’-GCTGGTGG-3’; it is a site where the Rec Bnuclease activity on the strand with the 3’-end is suppressed.
In the genomes of enteric bacteria Chi sites are recombinationhot spots. RecB acts as 3′-5′ helicase, nuclease.
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