a) A nonsense suppressor su1 in the E. coli genome acts on mutation 1 and 2 of g

Question

a)A nonsense suppressor su1 in the E. coli genome acts on mutation 1 and 2 of gene P in the T4 bacteriophage genome, but not on mutation 3. A different nonsense suppressor su2 works on mutation 3 of gene P, but not on mutation 1 or mutation 2. On further investigation, you find that su1 and su2 are both mutations in a tRNA-encoding gene. How is this possible?

b)Which type of deletion would have the smallest effect on the encoded protien? 1,2,3,4,or 5 nucleotides

c)Why does and insertion or deletion of a nucleotide in a gene case a larger change in the encoded protein than just changing a nucleotide from one base to another?

Explanation / Answer

(a) Assuming that the three mutations of gene T4 are all nonsense mutations, there are three different possible stop codons that might be the cause (amber, ochre, or opal). A suppressor mutation would be specific to one type of nonsense codon.

(b) 3 nucleotide deletion has smallest effect on the encoded protein

(c) insertion of deletion of a nucleotide (Indel) in a gene cause a larger change in the encoded protein because it causes a change in the gene sequence thereby causing a large change in the encoded protein. Whereas changing a nucleotide from one base to another has no effect on the phenotype of proyein thus there is no change in encoded protein.

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