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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
For the example of eye color, this would mean they both have brown eyes. They can produce gametes that contain either the B or the b allele. (It is conventional in genetics to use capital letters to indicate dominant alleles and lower-case letters to indicate recessive alleles.)
Rarer genetic conditions causing color blindness include congenital blue–yellow color blindness (tritan type), blue cone monochromacy, and achromatopsia. Color blindness can also result from physical or chemical damage to the eye, the optic nerve, parts of the brain, or from medication toxicity. [2] Color vision also naturally degrades in old ...
When it comes to eye color, the melanin controlled by the OCA2 gene is diluted and thus we all have blue eyes. For those with that blue-eye gene mutation they eyes stay blue.
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]
"His right eye was light blue, while the left was black, nevertheless his eyes were most attractive", is the description of the historian John Malalas. [ 33 ] [ 34 ] [ 35 ] A more recent example is the German poet, playwright, novelist, scientist, statesman, theatre director, and critic, Johann Wolfgang Goethe .
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.
Conversely, some phenotypes could be the result of multiple genotypes. The genotype is commonly mixed up with the phenotype which describes the result of both the genetic and the environmental factors giving the observed expression (e.g. blue eyes, hair color, or various hereditary diseases).