Question

Four children of a man and woman who are second cousins have too few teeth, which is an autosomal recessive condition called oligodontia caused by mutation in a gene called LTPB3 on chromosome 11. The affected individuals are also short, with increased bone density in the spine and skull. The protein that causes the symptoms by affecting certain bone cells is too short. The mutation in this family is most likely:________.
A) a missense mutation.
B) a nonsense mutation.
C) a duplication of the gene.
D) a replacement of all purines with pyrimidines.

Answer 1

Answer:

B) a nonsense mutation; this is because a nonsense mutation results in the change of a regular amino acid codon into a stop codon, which ceases translation. This fits with the problem's description of the protein that causes the symptoms as too short, as translation is the process by which proteins/polypeptides are created. A missense mutation would not be the answer because it still codes for an amino acid, which would not shorten the protein. A duplication of the gene would probably just lengthen the protein or not affect its length at all.