Question

Mutations in several different genes that encode enzymes in the pathway for the synthesis of the heme group may cause a genetic disorder called methemoglobinemia. The symptoms of this disorder range form mild to death in the most severe cases. The enzyme cytochrome b5 reductase is one of the enzymes in this pathway. This enzyme is responsible for reducing the iron in the heme group to the ferrous state so that it can bind oxygen. Kobayashi et al. reviewed several mutations in this gene. One of these mutations causes a Ser to Pro substitution. Explain what nucleotide change and in which position in the codon can cause this amino acid change. Assign all possible appropriate terms to this mutation.

Answer 1

Please find the explanation of the nucleotide change below

Step-by-step explanation:

Mutation is any change that occurs to the nucleotide sequence of a gene. According to this question, a substitution mutation which causes the Serine amino acid to change to Proline amino acid in the cytochrome b5 reductase enzyme is described.

A substitution mutation is a type of mutation in which one or more nucleotide base is replaced by another. The mRNA codons that specify Serine and Proline amino acids are as follows:

Serine: UCU, UCC, UCA, UCG, AGU, AGC

Proline: CCU, CCC, CCA, CCG

Based on the observation of these bases, URACIL BASE in the first four listed codons for serine amino acid is replaced by CYTOSINE BASE. i.e.

UCU (serine) -> CCU (proline)

UCC (serine) -> CCC (proline)

UCA (serine) -> CCA (proline)

UCG (serine) -> CCG (proline)

Notice that these base substitutions (U-C) occur in the 1st position of the codon.