NEET BIOLOGY

Detailed explanation-1: -An organism with two dominant alleles for a trait is said to have a homozygous dominant genotype. Using the eye color example, this genotype is written BB. An organism with one dominant allele and one recessive allele is said to have a heterozygous genotype. In our example, this genotype is written Bb.

Detailed explanation-2: -If the brown male had been BB, then all offspring would have been Bb and all brown. However, if the male is Bb as above and you perform a testcross, 50% of all offspring should have the bb genotype and a white phenotype.

Detailed explanation-3: -Homozygous alleles may be dominant or recessive. A homozygous dominant allele combination contains two dominant alleles and expresses the dominant phenotype (expressed physical trait). A homozygous recessive allele combination contains two recessive alleles and expresses the recessive phenotype.

Detailed explanation-4: -A heterozygous calf has one red allele and one black allele (Bb). These animals are always black. This tells you that the black allele is dominant and the red allele is recessive because the black coloration is hiding the red. We use “B” to indicate the dominant black allele and “b” for the recessive red allele.