Define the term Allele.
Topic: Allele
Answer
ALLELES are the alternative forms of the SAME GENE that occupy the same position (locus) on homologous chromosomes and control the same character, but express it in contrasting ways.
Three elements make a complete definition: SAME GENE, SAME POSITION on homologous chromosomes, CONTRASTING forms of one character.
An example costs one line and secures the mark: T and t for height in the pea plant.
The terms that follow from it, and which questions pair with this one: HOMOZYGOUS — both alleles alike (TT or tt), also called pure HETEROZYGOUS — alleles different (Tt), also called hybrid GENOTYPE — the alleles present (Tt) PHENOTYPE — the appearance produced (tall)
Note that a Tt plant LOOKS the same as a TT plant, because T is dominant — same phenotype, different genotype.
Example: in the gene for the height of a pea plant, T (tallness) and t (dwarfness) are alleles of each other.