Final answer:
Deleterious mutations negatively impact an organism's ability to survive and reproduce by potentially creating non-functional proteins, leading to medical conditions or genetic disorders.
Step-by-step explanation:
Deleterious mutations are changes to the genetic material that negatively impact an organism's fitness, which translates to its ability to survive and reproduce. Just like making a random change to a complex machine, such as a car engine, is unlikely to improve its function, random changes or mutations in an organism's DNA are more likely to produce proteins that do not function properly, if at all. These types of mutations can be particularly harmful because each cell relies on numerous proteins to function correctly at the right times and places. When critical proteins are affected by mutations, various medical conditions or genetic disorders can occur, including cancer. Mutations come in different forms, such as deletion and insertion mutations. A deletion mutation occurs when one or more nucleotides are lost from a DNA sequence. This can have a cascading effect, changing not just the codon from which the nucleotide was removed, but also every following codon, potentially leading to significant genetic diseases such as cystic fibrosis in some cases or cat cry syndrome. Conversely, beneficial mutations can help an organism adapt to its environment, although these are rare. Neutral mutations, on the other hand, do not affect an organism's fitness at all.