Mixed twins
Encyclopedia
Mixed twins are fraternal twins born to multiracial
families which differ in skin color
and other traits considered to be racial features.
From a biological point of view, the differences in these fraternal or dizygotic twins
from two biracial parents are not surprising. In humans, a relatively small number of genes
are thought to be responsible for human skin color
. Different alleles or gene variants code for differences in the melanin found within the skin. Within some groups we find high frequencies of dark skin alleles, while others have high frequencies of light skin alleles, for example. The parents of such twins, who are typically both of mixed race, have a combination of alleles for light and dark skin in their genome
.
Each sperm
or egg
cell will possess a random selection of genes from their mother or father. While not the most probable event, a sperm or egg may randomly acquire, for example, mostly alleles that confer light skin coloration or mostly alleles that confer dark skin coloration. In such cases we may find non-identical twins where twins differ from each other quite dramatically in terms of skin color or other physical characteristics.
There have been numerous sets of mixed twins.
Multiracial
The terms multiracial and mixed-race describe people whose ancestries come from multiple races. Unlike the term biracial, which often is only used to refer to having parents or grandparents of two different races, the term multiracial may encompass biracial people but can also include people with...
families which differ in skin color
Human skin color
Human skin color is primarily due to the presence of melanin in the skin. Skin color ranges from almost black to white with a pinkish tinge due to blood vessels underneath. Variation in natural skin color is mainly due to genetics, although the evolutionary causes are not completely certain...
and other traits considered to be racial features.
From a biological point of view, the differences in these fraternal or dizygotic twins
TWINS
Two Wide-Angle Imaging Neutral-Atom Spectrometers are a pair of NASA instruments aboard two United States National Reconnaissance Office satellites in Molniya orbits. TWINS was designed to provide stereo images of the Earth's ring current. The first instrument, TWINS-1, was launched aboard USA-184...
from two biracial parents are not surprising. In humans, a relatively small number of genes
Gênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...
are thought to be responsible for human skin color
Human skin color
Human skin color is primarily due to the presence of melanin in the skin. Skin color ranges from almost black to white with a pinkish tinge due to blood vessels underneath. Variation in natural skin color is mainly due to genetics, although the evolutionary causes are not completely certain...
. Different alleles or gene variants code for differences in the melanin found within the skin. Within some groups we find high frequencies of dark skin alleles, while others have high frequencies of light skin alleles, for example. The parents of such twins, who are typically both of mixed race, have a combination of alleles for light and dark skin in their genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
.
Each sperm
Spermatozoon
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...
or egg
Ovum
An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
cell will possess a random selection of genes from their mother or father. While not the most probable event, a sperm or egg may randomly acquire, for example, mostly alleles that confer light skin coloration or mostly alleles that confer dark skin coloration. In such cases we may find non-identical twins where twins differ from each other quite dramatically in terms of skin color or other physical characteristics.
There have been numerous sets of mixed twins.