Question

Point mutations can impair a protein if they result in a: (Select all that apply.) nonsense codon. synonymous codon. shift in reading frame. nonsynonymous codon.

Answer 1

Answer:

nonsense codon; shift in reading frame; nonsynonymous codon.

Explanation:

The mutation that affects the single nucleotide of nucleic acid are called as point mutation. It includes substitution, insertion or deletion of single base pair.

• When a premature nonsense or stop codon is inserted in the DNA sequence nonsense mutation occurs such as UAU is replaced by UAA (stop codon).
• A single nucleotide is added or deleted (shift in reading frame) in frame shift mutation.
• The amino acid are changed because of change in codon (nonsynonymous codon) by missense mutation.
• The mutation does not change the codon thus does not change the amino acid (synonymous codon) and does not express it are called as silent mutation.

Answer 2

Answer:

nonsense codon.. shift in reading frame. nonsynonymous codon.

Explanation:

Point mutation  is the type of mutation which cause  a  change  in   a single nucleotide  of a nucleic acid. It occurs  by replacing or substituting a single purine or pyrimidine on one DNA  strands  with   a  change in the corresponding purines and pyrimidine on the  other complementary DNA strands, and therefore synthesis of a different polypeptides protein chain.

E.g. Substitution of  amino acid  Glu. with Valine produces abnormal protein sequence which leads to sicked shaped haemoglobin  in sickle cell anemia.

When point mutations results from replacement of  single  nucleotides bases in DNA with   new uncomplimentary base  not  matching  the triplet code;it is refers to as  frame shift .It  results  in coding for an  entirely new amino  protein sequence. It also occurs by changing the first stop codon,(stop-gain or stop-loss) shifting the triplet code,producing short length of DNA sequence different from the original transcribed DNA sequence.  or extending the process of translation  due to loss of stop codon therefore entirely new longer length of proteins formed.

It can be due to  genetic effects  or  exposure to certain environmental factors.

Generally  when  a point mutation  results in a change in corresponding  amino acid sequence in the  protein from the original transcribed DNA sequence, non synonymous codon is formed. This is  non synchronous mutation.(Ka)(but if no  complementary change occurs it is refers to as( synonymous mutation( Ks).

A type of non-synonymous mutation is nonsense mutation from nonsense codon. It  occurs when point mutation results in  substitution of the original single base with a   stop codon; (stop-gain).Therefore the  base termination occurs  abruptly , shortened the length of the amino acid sequence and thus affecting the functions of the intended protein.