User:Cjp0001/sandbox

Clinical Implications
Different germline mutations can affect an individual differently depending on the rest of their genome. A dominant mutation only requires 1 mutated gene to produce the disease phenotype, while a recessive mutation requires both alleles to be mutated to produce the disease phenotype. For example, if the embryo inherits an already mutated allele from the father, and the same allele from the mother underwent an endogenous mutation, then the child will display the disease related to that mutated gene, even though only 1 parent carries the mutant allele. This is only one example of how a child can display a recessive disease while a mutant gene is only carried by one parent. Detection of chromosomal abnormalities can be found in utero for certain diseases by means of blood samples or ultrasound, as well as invasive procedures such as an amniocentesis. Later detection can be found by genetic testing.

Cancer
Mutations in tumour suppressor genes or proto-oncogenes can predispose an individual to developing tumours. It is estimated that genetic mutations are involved in 5-10% of cancers. These mutations make a person susceptible to tumour development if the other copy of the oncogene is randomly mutated. These mutations can occur in germ cells, allowing them to be heritable. Individuals who inherit germline mutations in TP53 are predisposed to certain cancer variants because the protein produced by this gene suppresses tumors. Patients with this mutation are also at a risk for Li-Fraumeni syndrome. Other examples include mutations in the BRCA1 and BRCA2 genes which predispose to breast and ovarian cancer, or mutations in MLH1 which predispose to hereditary non-polyposis colorectal cancer.

Huntington's Disease
Huntington's Disease is an autosomal dominant mutation in the HTT gene. The disorder causes degradation in the brain, resulting in uncontrollable movements and behavior. The mutation involves an expansion of repeats in the Huntingtin protein, causing it to increase in size. Patients who have more than 40 repeats will most likely be affected. The severity of the disease is correlated to the amount of repeats present in the mutation. Because of the dominant nature of the mutation, only one mutated allele is needed for the disease to be in effect. This means that if one parent is infected, the child will have a 50% chance of inheriting the disease. This disease does not have carriers because if you have one mutation, you will (most likely) be affected. The disease typically has a late onset, so many parents have children before they know they have the mutation. The HTT mutation can be detected through genome screening.

Trisomy 21
Trisomy 21 (also known as Down Syndrome) results from a child having 3 copies of chromosome 21. This chromosome duplication occurs during germ cell formation, when both copies of chromosome 21 end up in the same daughter cell in either the mother or father, and this mutant germ cell participates in fertilization of the zygote. Another, more common way this can occur is during the first cell division event after the formation of the zygote. The risk of Trisomy 21 increases with maternal age, with 35 being the first significant monitoring age known as a geriatric pregnancy. This disease can be detected by non-invasive as well as invasive procedures prenatally. Non-invasive procedures include scanning for fetal DNA through maternal plasma via a blood sample.

Cystic Fibrosis
Cystic Fibrosis is an autosomal recessive disorder that causes a variety of symptoms and complications, the most common of which is a thick mucus lining in lung epithelial tissue due to improper salt exchange, but can also affect the pancreas, intestines, liver, and kidneys. Many bodily processes can be affected due to the hereditary nature of this disease; if the disease is present in the DNA of both the sperm and the egg, then it will be present in essentially every cell and organ in the body; these mutations can occur initially in the germline cells, or be present in all parental cells. The most common mutation seen in this disease is ΔF508, which means a deletion of the amino acid at the 508 position. If both parents have a mutated CFTR (cystic fibrosis transmembrane conductance regulator) protein, then their children have a 25% of inheriting the disease. If a child has 1 mutated copy of CFTR, they will not develop the disease, but will become a carrier of the disease. The mutation can be detected before birth through amniocentesis, or after birth via prenatal genetic screening.