12. Why can the crossing of an
individual that manifests
dominant phenotype with
another that manifests
recessive phenotype (for the
same trait) determine
whether the dominant
individual is homozygous or
heterozygous?

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From the crossing of individual
having recessive phenotype
another having dominant phenotype (
the same trait) it possible to
determine whether dominant
individual is homozygous
heterozygous. This is true the
genotype of the individual is
obligatorily homozygous, example,
aa. If the individual is also
homozygous, , the F1 offspring will
only heterozygous (aa x = only
Aa). If other individual is
heterozygous will be two different
forms, Aa and aa the 1:1
proportion. So a recessive phenotype
appears the direct offspring the
individual that manifests
dominant is certainly
heterozygous.