You decide that. All you have to do is define them before you start. The dominant gene is denoted by a capital letter, the recessive one by a lower case letter. It is better to pick a letter which has different forms for the capital and lower case letters (like A and a; not S and s).
the dominant alleles are represented by uppercase letters and the recessive in lowercase letters.
The letters in a Punnett square represent the alleles that may be inherited from each parent. Capital letters represent dominant alleles. Lower-case letters represent recessive alleles.
You record dominant alleles with capital letters and recessives with lower case letters.
recessive alleles are the ones with small letters, for example in Rr, the recessive is the r.
A punnet square uses letters to represent dominant and recessive alleles.
Dominant alleles are shown by a capital letter and recessive alleles are lowercase letters.
Recessive alleles are represented by lowercase letters
capital letters, such as PP equals two dominant alleles, pp equals two recessive alleles.
Most of the time a recessive allele is expressed using lower case letters in comparision to the upper case dominant alleles.
The alleles of the parents. The two letters on each side are the two alleles of one parent. Dr. Claire DNA Diva
If it's not a heterozygous, the alleles would either be two capital letters (TT) or two lowercase letters (tt). This is because the organism has either both two dominant alleles or two recessive alleles.
homozygous dominant means two alleles that are the same that are capital letters, heterozygous recessive means that to alleles are different BUT the same letters in lower case. (alleles for gender) EX: TT, Tt is homozygous dominant tt, tt is heterozgous recessive
Actually, there aren't specific letters. The letters depend on the alleles. For example, if the alleles are A and a, then Aa would be heterozygous, since hetero means different. Homozygous, however, would be two of the same alleles, since homo means same. The homozygous would be AA or AA in this example. hope this helped!
They stand for the parents alleles
(T,T) if t is the letter used for that allele capital letters are used for dominant alleles and lowercase is for recessive.
The letters on the outside of the Punnett square stand for the alleles of each parent. One parent's alleles are written across the top of the square, and the other parent's alleles are written along the left side of the square. The pairs of alleles inside the square represent all the possible genotypes for their offspring.
Lower case letters in a Punnett square represent recessive alleles.