Why do you think a genotype is made up of two letters (like Ss or Tt)?

Question

Could it have anything to do with homologus chromosomes?

Answer 1

It has to do with the capital letter is the dominant trait, so if the're is a capital letter in the genotype, thats the trait it will have, so it S=curly hair and s=straight hair, the genotype would have to be ss to be curly. If the genotype was Ss or SS, the hair would be curly

Answer 2

It has a lot to do with homologous chromosomes. Since you have 2 chromosomes with the same genes on them, your genotype indicates the two alleles you have for a particular gene.