Answer:
B
Explanation:
Sickle cell anemia is a mutation of the red blood cells, caused by a missense mutation of the beta-haemoglobin gene.
This mutation is known as a missense mutation because it mistakes one amino acid, for another. Instead of having the codon read GAG, which codes for <u>glutamic acid</u>, the codon mutates to read GUG, which codes for the amino acid <u>valine</u>.
This seemingly small mutation, has a major overall effect on the structure of the beta-haemoglobin protein that is formed.
The other options explained:
A silent mutation happens when a codon changes, but the overall outcome leads to the same amino acid being produced (CUU and CUA both code for the amino acid leucine).
An insertion mutation happens when a nucleotide is unintentionally added into the chain of nucleotides. This can also lead to a frame-shift mutation, depending on the number of nucleotides have been added. Due to the fact that codons are read in sets of three, if three nucleotides are added next to each other, then that insertion mutation will have the effect of adding another amino acid to the chain, without changing anything else. However, if only one or two nucleotides are added, this insertion causes a frame-shift mutation which can alter the amino acids that come after it.
