You are studying regulation of the yeast enzyme glutamine synthetase (GS), which is encoded by the GLN1 gene. You have isolated two mutants, designated gln2– and gln3–, that give decreased GS activity. Mating of either gln2– or gln3– haploids to wild type produces heterozygous diploids that show normal amounts of GS expression. When you cross either a gln2– or gln3– haploid to a gln1– strain the resulting diploids show normal expression of GS.              

From these experiments,  Classify  the  gln2– and gln3– mutations in terms of their basic genetic properties explaining the rationale behind your conclusions. Based on these properties make a proposal for the types of regulatory functions affected by the gln2– and gln3– mutations.

#Question id: 4259

#Unit 3. Fundamental Processes

Rank the following one-base point mutations with respect to their likelihood of affecting the structure of the corresponding polypeptide (from most likely to least likely).

1. insertion mutation deep within an intron

2. substitution mutation at the third position of a codon in an exon

3. substitution mutation at the second position of a codon in an exon

4. deletion mutation within the first exon of the gene

#Question id: 4260

#Unit 3. Fundamental Processes

Which of the following occur(s) when the eukaryotic translational machinery encounters the TAG codon?

#Question id: 4261

#Unit 3. Fundamental Processes

Polyadenylation can promote translation

a. of the fragile-X gene.                     

b. of stored oocyte mRNAs.

c. by allowing for greater interaction at the 5´ end.

d. by allowing for greater interaction with translation initiation factors.

#Question id: 4262

#Unit 3. Fundamental Processes

Find the correct series of event of translation termination

#Question id: 4263

#Unit 3. Fundamental Processes

For the classes of AATS, which of following statement is correct

#Question id: 4264

#Unit 3. Fundamental Processes

A classic biochemical experiment nicely illustrated the point that the ribosome recognizes tRNA and not the amino acid that it is carrying. In that following observation were made. Which of them can be correct.

A. The cysteine attached to cysteine-tRNACys can be converted to an alanine by chemical reduction to give alanine-tRNACys.

B. Alanine-tRNACys introduces alanines at codons that specify insertion of cysteine.

C. Different mechanism is used to incorporate selenocyteine on tRNA as selenocysteine is incorporated into proteins by chemical modification after translation

D. Selenocysteine is generated enzymatically from serine carried on a special tRNA that is charged by serine-tRNA synthetase

E. Above examples can conclude that the translation machinery relies on the high fidelity of the aminoacyl-tRNA synthetases to ensure the accurate decoding of each mRNA