Thu October 27, 2011 By:

Please explain alleles clearly, And why always 4 plants are formed in F1 generation when we cross TT with tt? why not 5, 6, 7.. ?

Expert Reply
Sun October 30, 2011
Alleles refer to either of a pair (or series) of alternative forms of a gene that occupies the same locus on a particular chromosome and that control the same character.  Different alleles produce variations in inherited characteristics such as eye color or blood type. Paired alleles (one on each of two paired chromosomes) that are the same are called homozygous, and those that are different are called heterozygous. In heterozygous pairings, one allele is usually dominant, and the other recessive.
It is not 4 plants, which are being shown in F1, but the various possible combinations of plants in F1 generation.
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