Gene Mutations and Their Effects — NEET Biology
📚 Practice ConceptThe relationships between genes and DNA are best understood by mutation studies. You have studied about mutation and its effect in Chapter 4. Effects of large deletions and rearrangements in a segment of DNA are easy to comprehend. It may result in loss or gain of a gene and so a function. The effect of point mutations will be explained here. A classical example of point mutation is a change of single base pair in the gene for beta globin chain that results in the change of amino acid residue glutamate to valine. It results into a diseased condition called as sickle cell anemia. Effect of point mutations that inserts or deletes a base in structural gene can be better understood by following simple example.
Which of the following statements correctly describe the consequences of different types of point mutations, considering the properties of the genetic code? S1. A silent mutation, such as the change from UAU to UAC (both coding for Tyrosine), results in no change in the amino acid sequence of the polypeptide due to the degeneracy of the genetic code. S2. A missense mutation occurs when a single base change leads to the formation of a premature stop codon, thereby shortening the polypeptide chain. S3. The change of a single base pair in the gene for the beta-globin chain from GAG to GUG, causing Glutamate to change to Valine, is an example of a missense mutation. S4. Frameshift mutations are always more severe than point mutations because they alter the reading frame from the point of insertion or deletion, affecting all downstream amino acids. S5. The non-overlapping nature of the genetic code means that a point mutation (single base change) will only affect the amino acid coded by that specific codon, without impacting adjacent codons
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