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Gene duplication (or chromosomal duplication or gene amplification) is a major mechanism through which new genetic material is generated during molecular evolution.It can be defined as any duplication of a region of DNA that contains a gene.
CAH can occur in various forms. The clinical presentation of each form is different and depends to a large extent on the kind of the underlying 21-hydroxylase enzyme defect. [9] Classical forms appear in infancy, and nonclassical forms appear in late childhood. The presentation in patients with classical CAH can be further subdivided into two ...
XX gonadal dysgenesis is a type of female hypogonadism in which the ovaries do not function to induce puberty in a person assigned female at birth, whose karyotype is 46,XX. [1] Individuals with XX gonadal dysgenesis have normal-appearing external genitalia as well as Müllerian structures (e.g., cervix, vagina, uterus).
In genetics, a maternal effect occurs when the phenotype of an organism is determined by the genotype of its mother. [1] For example, if a mutation is maternal effect recessive, then a female homozygous for the mutation may appear phenotypically normal, however her offspring will show the mutant phenotype, even if they are heterozygous for the mutation.
An example of a birth defect is cleft palate, which occurs during the fourth through seventh weeks of gestation. [14] Body tissue and special cells from each side of the head grow toward the center of the face. They join to make the face. [14] A cleft means a split or separation; the "roof" of the mouth is called the palate. [15]
It shows 22 homologous autosomal chromosome pairs, both the female (XX) and male (XY) versions of the two sex chromosomes, as well as the mitochondrial genome (at bottom left). In genetics , a chromosomal rearrangement is a mutation that is a type of chromosome abnormality involving a change in the structure of the native chromosome . [ 1 ]
A karyotype of an individual with trisomy 21, showing three copies of chromosome 21.. An abnormal number of chromosomes is known as aneuploidy, and occurs when an individual is either missing a chromosome from a pair (resulting in monosomy) or has more than two chromosomes of a pair (trisomy, tetrasomy, etc.).
During nonfunctionalization, or degeneration/gene loss, one copy of the duplicated gene acquires mutations that render it inactive or silent. Non-functionalization is often the result of single gene duplications. [11] At this time, the gene has no function and is called a pseudogene. Pseudogenes can be lost over time due to genetic mutations.