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Blue eyes are a highly sexually dimorphic eye color. Studies from various populations in Europe have shown that men are substantially more likely to have blue eyes than women. [18] The inheritance pattern followed by blue eyes was previously assumed to be a Mendelian recessive trait, though this has been
Waardenburg syndrome is a group of rare genetic conditions characterised by at least some degree of congenital hearing loss and pigmentation deficiencies, which can include bright blue eyes (or one blue eye and one brown eye), a white forelock or patches of light skin.
The ancestral allele is linked to darker pigmentation and dominant over the lighter pigment recessive allele. [10] [11] The rs12913832 SNP, located in intron 86 of the HERC2 gene contains a silencing sequence that can inhibit the expression of OCA2 and, if both recessive alleles are present, can homozygously cause blue eyes. [12]
Albinism results from inheritance of recessive gene alleles and is known to affect all vertebrates, including humans. It is due to absence or defect of tyrosinase , a copper-containing enzyme involved in the production of melanin .
Blue cone monochromacy (BCM) is an inherited eye disease that causes severe color blindness, poor visual acuity, nystagmus, hemeralopia, and photophobia due to the absence of functional red (L) and green (M) cone photoreceptor cells in the retina. BCM is a recessive X-linked disease and almost exclusively affects XY karyotypes.
Besides the TYR gene, several other genes can cause albinism. This is because other hormones and proteins are involved in melanin production, the presence of which is genetically determined. In mice, a total of 100 genes are known to affect albinism. [20] Most forms of albinism follow a recessive pattern of inheritance. [21]
The reason boils down to genes. A senior lecturer in biomolecular sciences at Liverpool John Moores University said, "What we know now is that eye color is based on 12 to 13 individual variations ...
P protein, also known as melanocyte-specific transporter protein or pink-eyed dilution protein homolog, is a protein that in humans is encoded by the oculocutaneous albinism II (OCA2) gene. [5] The P protein is believed to be an integral membrane protein involved in small molecule transport, specifically of tyrosine —a precursor of melanin .