Final answer:
Trinucleotide repeat expansions lead to genetic diseases by producing abnormal proteins with repeated amino acid sequences, as seen in Huntington's disease. Genetic diseases can also result from chromosome anomalies like Down syndrome's trisomy 21. These mutations are inheritable, causing diseases to be passed down from parents to children.
Step-by-step explanation:
Trinucleotide Repeat Expansions
Trinucleotide repeats are sequences in DNA where a set of three nucleotides is repeated several times in tandem. When these trinucleotide repeats expand beyond a normal threshold, it can lead to genetic diseases. This expansion can result in a gene producing an abnormal protein with a string of the same amino acid, which can disrupt the protein's normal function. Huntington's disease is an example of such a disorder, where repeats of the CAG trinucleotide result in an abnormal protein containing an elongated glutamine chain, eventually causing neurodegenerative issues.
In cases of mutations like insertions or deletions, if they cause a frameshift in the coding sequence, the resulting protein is often nonfunctional. On the other hand, genetic disorders such as Down syndrome are not caused by specific gene mutations but by an incorrect number of chromosomes, like having an extra chromosome 21 (trisomy 21).
Mutations can be inherited, which is how a genetic disorder could be passed down from parents to children. In some cases, mutations leading to disorders like sickle cell disease and cystic fibrosis are due to specific changes in the DNA code that alter a protein's structure and function.