Question

Most novel mutations that occur in humans do not directly cause human disease. Which of the following is a reason why?

A) most mutations are gain-of-function, and these make genes work better
B) most mutations are single nucleotide changes, and changing a single nucleotide cannot cause a disease
C) genes represent only around 10% of your DNA, so 90% of mutations will not affect any genes
D) disease-causing mutations are repaired quickly, while non-disease-causing mutations are not
E) mutations give you superpowers, not diseases

Answer 1

Most novel mutations in humans do not cause disease because they often occur in non-coding DNA or result in synonymous changes, and not all amino acid changes affect protein function; some can even be beneficial.

Step-by-step explanation:

One significant reason why most novel mutations do not directly cause human disease is that genes represent only a fraction (approximately 10%) of the total DNA in humans. Considering that a large part of our DNA does not consist of genes but rather consists of non-coding regions, the chances of a mutation occurring within an actual gene are relatively small. Out of those mutations that occur within genes, not all will result in changes to the amino acids in proteins. This is because of the redundancy in the genetic code where multiple codons can encode for the same amino acid, making some single nucleotide changes synonymous (no change in the produced amino acid).

Furthermore, not all amino acid changes will result in a malfunctioning protein. Protein function might only be affected if the mutation changes an amino acid that is critical for the protein's structure or function. A mutation in a non-essential part of the protein may have no functional consequence. Additionally, some mutations can even be beneficial, providing an advantage in certain environments, though these are much less common.

Mutations involving insertions, deletions, or nonsense mutations can be more drastic, potentially leading to a frameshift or premature stop codon. However, these types of mutations are rarer and the cellular mechanism often can identify and correct errors or destroy improperly formed proteins.