Search results
Results From The WOW.Com Content Network
[8] One mutant allele for achondroplasia can be tolerated, but having two results in death. In the case of homozygous achondroplasia, death almost invariably occurs before birth or in the perinatal period. Not all heterozygotes for recessive lethal alleles will show a mutant phenotype, as is the case for cystic fibrosis carriers. If two cystic ...
The following is a list of genetic disorders and if known, type of mutation and for the chromosome involved. Although the parlance "disease-causing gene" is common, it is the occurrence of an abnormality in the parents that causes the impairment to develop within the child. There are over 6,000 known genetic disorders in humans.
Sex chromosome anomalies belong to a group of genetic conditions that are caused or affected by the loss, damage or addition of one or both sex chromosomes (also called gonosomes). In humans this may refer to: 45, X, also known as Turner syndrome; 45,X/46,XY mosaicism, also known as X0/XY mosaicism and mixed gonadal dysgenesis; 46, XX/XY
A genetic disorder is a health problem caused by one or more abnormalities in the genome.It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosome abnormality.
Mendelian traits behave according to the model of monogenic or simple gene inheritance in which one gene corresponds to one trait. Discrete traits (as opposed to continuously varying traits such as height) with simple Mendelian inheritance patterns are relatively rare in nature, and many of the clearest examples in humans cause disorders.
In 1990, George Brownlee and Merlin Crossley showed that two sets of genetic mutations were preventing two key proteins from attaching to the DNA of people with a rare and unusual form of haemophilia B – haemophilia B Leyden – where patients experience episodes of excessive bleeding in childhood but have few bleeding problems after puberty ...
Rather than having monosomy, or only one copy, the majority of aneuploid people have trisomy, or three copies of one chromosome. [ citation needed ] An example of trisomy in humans is Down syndrome , which is a developmental disorder caused by an extra copy of chromosome 21; the disorder is therefore also called trisomy 21.
Another example is the haploinsufficiency of telomerase reverse transcriptase which leads to anticipation in autosomal dominant dyskeratosis congenita. It is a rare inherited disorder characterized by abnormal skin manifestations, which results in bone marrow failure , pulmonary fibrosis and an increased predisposition to cancer.