THE MOLECULAR BASIS OF INHERITANCE
GENE MUTATION
|
Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
|
|
|
missense mutation
|
|
|
insertion mutation
|
|
|
chromosomal mutation
|
|
|
non-sense mutation
|
Detailed explanation-1: -Definition. A nonsense mutation occurs in DNA when a sequence change gives rise to a stop codon rather than a codon specifying an amino acid. The presence of the new stop codon results in the production of a shortened protein that is likely non-functional.
Detailed explanation-2: -Stop codons are also called nonsense codons because they do not code for an amino acid and instead signal the end of protein synthesis. Thus, nonsense mutations occur when a premature nonsense or stop codon is introduced in the DNA sequence.
Detailed explanation-3: -Stop codon suppression or translational readthrough occurs when in translation a stop codon is interpreted as a sense codon, that is, when a (standard) amino acid is ‘encoded’ by the stop codon. Mutated tRNAs can be the cause of readthrough, but also certain nucleotide motifs close to the stop codon.
Detailed explanation-4: -There are 3 STOP codons in the genetic code-UAG, UAA, and UGA. These codons signal the end of the polypeptide chain during translation. These codons are also known as nonsense codons or termination codons as they do not code for an amino acid.
Detailed explanation-5: -A stop codon is a sequence of three nucleotides (a trinucleotide) in DNA or messenger RNA (mRNA) that signals a halt to protein synthesis in the cell.