Task 2. The protein contains the amino acid valine. As a result of mutations in the DNA molecule, the replacement occurred in one nucleotide. The triplet encoding the amino acid - cysteine encoded by the UGU triplet is replaced by the UGA triplet. This replacement results in ______________ mutations.
Cysteine amino acid is encoded by two triplets: UGU and UGC. The replacement of the third nucleotide of UGU triplet by nucleotide A leads to the replacement of triplet encoding cysteine by premature stop codon UGA. The consequence of such replacement is abnormally short protein and loss of its function.
The mutations that affect a single nucleotide are called point mutations. The mutations that are caused by the replacement of a pyrimidine base (U) by purine base (A) are called transversions. The mutations that lead to the appearance of premature stop codons are called nonsense mutations.
This replacement results in point (transversion), nonsense mutations.