Genetics Question: Brenner

Answer the following questions and prepare notes on the study guide for Brenner's paper on Caenorhabditis Elegans Genetics.

• Questions.pdf

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1. EMS mutagenesis: What are the most common types of mutations caused by EMS? For this type of mutation, what codons would be mutated by EMS in a single base change and what would they now encode? Are there any codons that cannot be mutated by EMS? Are there any codons that cannot be made by EMS mutagenesis? What amino acids do they encode? Can the most common action of EMS mutate a stop codon away?


EMS produces random mutations in genetic material by guanine alkylation resulting in nucleotide substitution. This produces point mutations only. It can induce mutations even without substantial killing at a rate of 5x10−4 to 5x10−2 per gene. The guanine in DNA causes the reaction with ethyl group of EMS reacts, forming the base O-6-ethylguanine, which we don’t find in normal scenario. DNA Polymerase which plays a key role during DNA replication frequently place thymine, instead of cytosine, opposite O-6-ethylguanine. Following subsequent rounds of replication, the original G:C base pair can become an A:T pair (a transition mutation). This changes the genetic information can result in the disease as they are often harmful to cells, depending on the genetic position where the mutation is taking place.
Codons A T cannot be mutated by EMS....