3-5. Several mutant E. coli or mouse alleles are described below. For each, answ

Question

3-5. Several mutant E. coli or mouse alleles are described below. For each, answer (a) and (b): (a) Predict the mutant phenotype, focusing on the molecular phenotype (the effect on relevant process, for example DNA replication). Describe whether you expect the process would be disrupted completely or partially, and in what way it would be changed. You don't need to speculate about the whole-organism phenotype )Predict whether the mutation would ber (Although E. coli is haploid, assume that you can generate cells diploid for the gene in question one copy of the gene has the mutation listed, and the other copy is wild-type). Assume no haploinsufficiency or dominant to a wild-type allele. 3. A mutation in the coding sequence of dnaA. The mutant DnaA protein can still bind DNA normally, but it can't bind at all to other DnaA proteins (2 points) 4. A mutation in the dnaA coding sequence that encodes a mutant protein that cannot bind either DNA or other DnaA proteins. (2 points) 5. A mutation in the Rho gene, such that the mutant Rho protein translocates along RNA 1000x more quickly than the wild-type Rho protein. (2 points)

Explanation / Answer

3a) DnaA protein initiates DNA replication by forming a specific DnaA-oriC complex. Replication is initiated with the cooperative binding of 10 to 20 DnaA monomers to 9-mer of the Ori site. So the replication will not be disrupted completely, if DnaA protein can't bind to other DnaA proteins.

4a) DnaA binding to the ori site opens or melts the double helix within three At rich, 13 nucleotide repeats located at the Ori site, that leads to the recruitment of helicase. So if DnaA do not bind either to DNA or other DnaA protein then the replication will be completely disrupted.

The mutations are recessive in case of diplod cells- containing one wild phenotype and one mutant, as the wild type gene is sufficient to produce normal product.

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