Question

genes which code for a pair of contrasting traits are known as

Answer 1

they're known as alleles

Answer 2

Alleles are pair of contrasting characters for a single trait.They occupy same position [locus] on homologous chromosomes. Alleles are represented by alphabets and recessive with small. In gaeden pea height [character]:- tallness {trait} is dominant over dwarfness {contrasting trait} .So allele for tallness is "T" and for dwarfness is "t". Genotype for tallness may either be homozygous" TT" or heterozygous "Tt" but recessive character dwarfness will only be expressed in individuals having both alleles "tt".[homozygous recessive].