Question

When can a mutation in only one of the alleles for a locus in a diploid cell have devastating effects for that cell ?

Group of answer choices

When the mutation affects a haploinsufficient locus

When it causes a synonymous mutation in the protein region of a gene

When it completely abolishes the expression of the mutated allele

When it causes a nonsense mutation downstream of the stop codon of a protein-coding gene

When it affects the coding sequence of a gene that is not normally expressed in a that cell

Answer 1

When the mutation affects a haploinsufficient locus

Disorders caused by haploinsufficient genes usually have a dominant inheritance pattern.  Haploinsufficiency may arise from a de novo or inherited loss-of-function mutation in the variant allele, such that it produces little or no gene product (often a protein). Although the other, standard allele still produces the standard amount of product, the total product is insufficient to produce the standard phenotype.

As far as the rest of the choices are concerned-

Synonymous mutation does not change the expression of gene i.e it codes for the same protein.

Abolishing the expression of mutated allele means that the mutated effect of the gene is reversed and the all is back to normal.

Nonsense mutation means the introduction of a stop codon but if this introduction is introduced downstream of the stop codon, it will produce no effect.

If the mutation affects the coding strand then the effect will not be devastating as the coding strand doe not codes for the gene expression, in fact, template strand codes for it.