Asked Nov 13, 2019

What would the effect be if there was a substitution of one nucleotide for another?


Expert Answer

Step 1


These are the building blocks or structural component of the deoxyribonucleic acid or DNA and ribonucleic acid or RNA. A nucleotide consists of a base (one of four chemicals: adenine, thymine, guanine, and cytosine) plus a molecule of sugar and one of phosphoric acid.

Step 2

A point mutation:

When one nucleotide is exchanged for another, then a point mutation takes place.

It is a genetic mutation in which one single nucleotide base is altered, deleted or inserted from a DNA or RNA sequence. Due to this mutation there is a change within a gene because whole of the DNA sequence is modified. These mutations usually result form the errors during the DNA replication and by the exposure to ultraviolet radiation or the X-rays.

For example:

Sickle-cell disease is occurring due to a single point mutation in the beta-hemoglobin gene. GAG codon is converted into GUG, that abnormally codes the valine amino acid rather than the glutamic acid.

Step 3

Some possible effects due to point mutations:

  1. Point mutations occurring at the non-coding sequence sites are mostly without any consequences, though there are exceptions.

When the mutated base pair lies in the gene’s promoter sequence, then the expression of the gene might show variation. When the mutation takes place in the splicing region of an intron, then it might hinder with the accurate splicing of the pre-mRNA.

  1. Due to this mutation in one amino acid, the entire peptide might vary. Thus, it modifies the entire protein.

And if this protein has a special role in cellular reproduction then this single point mutation can modify the entire cellular reproduction process for this organism.

  1. Some of these mutations prove to be useful and some harmful. If these are germline mutations, then it can result in adaptations and ultimately to an evolution. While the harmful mutations lead to the death of an organisms or be fewer liable to reproduce in a phenomenon of natural selection.
  2. There occurs ...

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