Question:

What would happen if in a gene encoding apolypeptide of $50$ amino acids has UAC at $25^{th}$ position mutated to UAA ?

Updated On: Jul 12, 2022
  • A polypeptide of 25 amino acids will be formed
  • A polypeptide of 24 amino acids will be formed
  • A polypeptide of 49 amino acids will be formed
  • Two polypeptides of 24 and 25 amino acids will be formed
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The Correct Option is B

Solution and Explanation

UGA, UAG and UAA are three non sense (or termination) codon which do not code for any amino acid. If in a gene encoding a polypeptide of 50 amino acid, 25lh codon is mutated to UAA or any of the termination codon, then the chain will be terminated at that place because it will become difficult for /RNA to bring amino acid from amino acid pool. So in that case a polypeptide of 24 amino acid will be formed.
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Concepts Used:

The Molecular Basis of Inheritance

DNA Replication:

DNA synthesis is commenced at particular points within the DNA strand referred to as ‘origins’, which are certain coding regions. There are numerous origin sites, and when replication of DNA starts, these sites are mentioned as replication forks. Within the replication, the complex is the enzyme DNA Helicase, so that they can be utilized as a template for replication. DNA Primase is another enzyme that's essential in DNA replication.

RNA:

Ribonucleic acid (RNA) is an essential biological macromolecule that exists all together in biological cells. It is principally involved in the synthesis of proteins, that carry the messenger instructions from DNA, which itself contains the genetic instructions needed for the event and maintenance of life. In some viruses, RNA, in spite of DNA, carries genetic information.

Genetic Code:

Genetic code is the term we use in the manner that the four bases of DNA--the A, C, G, and Ts--are strung together in a way that the ribosome, the cellular machinery, can read them and switch them into a protein. In the ordering, every three nucleotides during a row count as a triplet and code for one amino alkanoic acid.

Read More: Molecular Basis of Inheritance