Write an article based on this "Understand genes and genotypes. Draw a 2 x 2 grid. Label the top of the square with one parent genotype. Label the left side of the square with the other parent genotype."
A genotype is the heritable, genetic code of an individual. An individual's genotype comes from the alleles on the two chromosomes inherited from their parent. An allele is the specific form of a gene. For example, a gene codes for hair color but one allele could code for blonde hair, while another codes for brown hair. Every individual has two chromosomes with two alleles that make their genotype so it is represented with two letters. Capital letters indicate dominant alleles while lowercase letters represent recessive alleles. It doesn't matter what letter you choose to represent your gene of interest, so choose something that makes sense to you. Usually, the first letter of the dominant allele is used. For example, B represents the dominant gene for brown hair and b represents the recessive gene for blonde hair. As its name suggests a Punnett square is just a divided square. Draw your square and divide it into four smaller squares by drawing two lines (one horizontal and one vertical) through the center of the square. Leave enough room in each box for two letters. Also, leave room at the top and left side of the square. For example, let's say the mother has brown hair and a genotype of Bb, then you would put a B over the top left-hand square and a b over the top right-hand square. It doesn't matter where you put each parent's genotype. Only one letter goes above each column. For example, if the father also has brown hair, but his genotype is BB, you would put one B to the left of the upper left-hand square, and another B to the left of the lower left-hand square.