Question

A change within a single base pair in DNA is least likely to be observed if the change affects

Answer 1

A change within a single base pair in DNA is least likely to be observable if the change affects an unexpressed recessive trait. Hence the correct option is b.

A change within a single base pair in DNA is least likely to be observable if it affects an unexpressed recessive trait. In a diploid organism, each individual possesses two alleles for a particular trait, and the effect of a single base pair change may be masked if the altered allele is recessive and the other allele is dominant. Recessive traits are only expressed phenotypically when an individual carries two copies of the altered allele.

In the case of an unexpressed recessive trait, the presence of a single changed base pair may not result in a noticeable phenotypic change, as the dominant allele prevails in determining the observable trait. This scenario is in contrast to situations involving stop codons, codominant alleles, or sex-linked traits, where a change in a single base pair can have more readily observable effects. Hence the correct option is b.

Complete ques:

A change within a single base pair in DNA is least likely to be observable if the change affects-

A. the production of a stop codon

B. an unexpressed recessive trait

C. actions of a codominant allele

D. the expression of a sex-linked trait

Answer 2

Step-by-step explanation:

A point mutation is a change within a gene in which one base pair in the DNA sequence is altered 1. Point mutations are frequently the result of mistakes made during DNA replication, although modification of DNA, such as through exposure to X-rays or to ultraviolet radiation, also can induce point mutations 1.

Point mutations can be classified into three types: silent, missense, and nonsense mutations 2. A silent mutation is a change in the DNA sequence that does not result in a change in the amino acid sequence of the protein that is produced 2. A missense mutation is a change in the DNA sequence that results in a different amino acid being incorporated into the protein 2. A nonsense mutation is a change in the DNA sequence that results in a premature stop codon, which leads to the production of a truncated protein 2.

Therefore, a change within a single base pair in DNA is least likely to be observed if the change affects a non-coding region of the DNA or if the change is a silent mutation 12.