Talk:Yang Xiao Long/@comment-172.56.39.128-20140905022408/@comment-1909619-20141010215032

This is mostly in response to PennywiseTheEternal, but I feel that most of the people on this wikia need some background in genetics. A black haired male and a black haired female CAN give birth to a blonde haired child. This happens in real life, and isn't limited to hair color, but eye color and other things as well.

This is called  a Punnett Square: http://imgur.com/x8Bmvgl

The upper and lowercase H's refer to alleles for Hair color, which you can think of as genes. The uppercase H is DOMINANT and for black hair. The lowercase h is RECESSIVE and for blonde hair. If both parents carry the recessive allele AND the dominant allele then we say that they are GENOTYPICALLY heterozygous. That's just a fancy way of saying they both have an H and an h gene (one from each of their parents). We'll just call mom Hh and Dad Hh then because they have the same makeup.

Because H (black hair) is dominant, all it takes is having one allele to have black hair, which is why the parents have black hair. To have a blonde child they need to pass BOTH of their recessive alleles to their offspring. If they have kids these four boxes in my link show every combination they can make. So they have a 75% chance of having a black-haired child and a 25% chance of having a blonde haired child.

For the record, we would say that the GENOTYPIC ratio in the punnett square is 1:2:1 because we have a 25% chance of a black-haired HOMOZYGOUS (both alleles match), 50% chance of a black-haired HETEROZYGOUS, and 25% chance of a blonde-haired homozygous child.

We would also say that the PHENOTYPIC ratio (PHENOTYPE means how things look, not what they are genetically) would be 3:1 because we would have a 75% chance of getting a black-haired child and 25% chance of getting a blonde-haired child.