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Sex linked describes the sex-specific reading patterns of inheritance and presentation when a gene mutation is present on a sex chromosome (allosome) rather than a non-sex chromosome . In humans, these are termed X-linked recessive , X-linked dominant and Y-linked .
Genetic linkage is the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction.Two genetic markers that are physically near to each other are unlikely to be separated onto different chromatids during chromosomal crossover, and are therefore said to be more linked than markers that are far apart.
X-linked recessive inheritance. X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be always expressed in males (who are necessarily hemizygous for the gene mutation because they have one X and one Y chromosome) and in females who are homozygous for the gene mutation, see zygosity.
Individuals can develop a recessive trait in the phenotype dependent on their sex—for example, colour blindness and haemophilia (see gonosomal inheritances). [ 7 ] [ 8 ] As many of the alleles are dominant or recessive, a true understanding of the principles of Mendelian inheritance is an important requirement to also understand the more ...
Y-linked inheritance Pedigree tree showing the inheritance of a Y-linked trait. Y linkage, also known as holandric inheritance (from Ancient Greek ὅλος hólos, "whole" + ἀνδρός andrós, "male"), [1] describes traits that are produced by genes located on the Y chromosome. It is a form of sex linkage. Y linkage can be difficult to detect.
Sex linkage was first reported by Doncaster and Raynor in 1906 [2] who studied the inheritance of a colour mutation in a moth, Abraxas grossulariata. Thomas Hunt Morgan later showed that a new white-eye mutation in Drosophila melanogaster was also sex-linked. He found that a white-eyed male crossed with a red-eyed female produced only red-eyed ...
There are two distinctive mapping approaches used in the field of genome mapping: genetic maps (also known as linkage maps) [7] and physical maps. [3] While both maps are a collection of genetic markers and gene loci, [8] genetic maps' distances are based on the genetic linkage information, while physical maps use actual physical distances usually measured in number of base pairs.
Mutations inherited through the chromosomes can be autosomal dominant or recessive and can also be sex-linked dominant or recessive. Chromosomal inheritance follows normal Mendelian laws, despite the fact that the phenotype of the disease may be masked.