Question

13.

A) A change to a single base pair in the sequence of a DNA molecule is called a ______ mutation.

B) If that single nucleotide change results in a protein with the exact same amino acid sequence it is called a _________ mutation.

C) If the base pair change results in an alteration of the amino acid sequence of the protein it is called a ___________ mutation.

D) If the base pair changes results in a codon for an amino acid being changed into a stop codon it is called a ________ mutation.

Answer 1

Ans-A. Point

A point mutation is a genetic mutation where single nucleotide base sequence is changed, inserted or deleted from a sequence of DNA. Thus it involves substitution of one base for other. It is of three types - silent, missense and nonsense mutation.

B. Silent

Silent mutation is a change in nucleotide base sequence but no change in amino acid. This means same amino acid is substituted which therefore does not change the protein. Example codon AAA is changed to AAG , same amino acid lysine is incorporated into protein.

C. Missense

It is the type of point mutation where there is change in single nucleotide base pair and there is change from.amino acid sequence to another. Example of this type is sickle cell anemia where there is missense mutation in single base pair and results in different protein . This means here GAG us changed to GUG resulting in different amino acid and different protein.

D. Non sense

- A nonsense mutation is a type of point mutation where there is a change in one DNA base pair. Here for one amino acid sequence instead of substituting another amino acid, it is being changed to stop codon.Due to stop codon, the cell stops forming the protein.