Human genetics

Human genetics is the study of intherintace as it occurs in human beings. Human genetics encompasses a variety of overlapping fields including: classical genetics, cytogenetics, molecular genetics, biochemical genetics, genomics, population genetics, population genetics, developmental genetics, clinical genetics, and genetic counseling. Genes can be the common factor of the qualites of most human-inherited traits. Study of human genetics can be useful as it can answer quesion about human nature, understand the disease and development of effective disease treatment, and understand genetics of human life.




Autosomal dominant inheritance

Autosonal traits are associated with a single gene on an autosome (non-sex chromosome)-they are called "dominant" because a single copy - inherited from either parent- is enough to cause this trait to appear. This often means thet one of the parents must also have the same trait, unless it has arisen due to a new mutation. Example of autosomal dominant traits and disorder are Huntington's disease, and achondroplasia.

Autosomal recessive inheritance

Autosomal recessive traits is one pattern of inheritance for a trait, disease, or disorder to be passed on through families. For a recessive trait or disease to be displayed two copies of the trait or disorder needs to be presented. The trait or gene will be located on a non-sex chromosome. Because it takes two copies of a trait to display a trait, many people can unknowingly be carriers of a disease. From an evolutionary perspective, a resseive disease or trait can remain hidden for are albinism, Crytic Fibrosis, Tay-Sachs disease.

X-linked and Y-linked inheritance

X-linked genes are found on the sex X chromosome. X-linked genes just like autosomal genes have both dominant and recessive type. Recessive X-linked disorders are rarely seen in females and  usually only affect males. This is because males inherit their X chromosome and all X-linked genes will be inherited from the maternal side. Fathers only pass on their Y chromosome to their sons, so no X-linked traits will be inherited from father to son. Females express X-linked disorders when they are homozygous for the disorder and become carriers when they are heterozygous. X-linked dominant inheritance will show the same phenotype as a heterozygote and homozygote. Just like X-linked inheritance, there will be a lack of male-to-male inheritance, which makes it distinguishable from autosomal traits. One example of a X-linked trait is coffin-lowry syndrome, which is caused by a mutation in ribosomal protein gene. This mutation results in skeletal, craniofacial abnormalities, mental retardation, and short stature.

X chromosomes in females undergo a process known as X inactivation. X inactivation is when one of the two X chromosomes in females is almost completely inactivated. It is important that this process occurs otherwise a woman would produce twince the amount of normal X chromosome proteins. The mechanism for X inactivation will occur during the embryonic stage. For people with disorders like trisomy X, where the genotype has three X chromosomes, X-inactivation will inactivate all X chromosomes until there is only one X chromosome active. X inactivation is not only limited to females, males with klinefelter syndrome, who have an extra X chromosome, will also undergo X inactivation to have only one completely active X chromosome.

Y-linked inheritance occurs when a gene, trait, or disorder is transferred through the Y chromosome. Since Y chromosomes can only be found in males, Y linked traits are only passed on from father to son. The testis determining factor, which is located on the Y chromosome, detrmines the maleness of individuals. Besides the maleness inherited in the Y-chromosome there are no other found Y-linked characteristics.