AP BIOLOGY

Detailed explanation-1: -Genotypes are described as homozygous if there are two identical alleles at a particular locus and as heterozygous if the two alleles differ.

Detailed explanation-2: -The expected genotype ratio when two heterozygotes are crossed is 1 (homozygous dominant) : 2 (heterozygous) : 1 (homozygous recessive). When a phenotypic ratio of 2 : 1 is observed, there is probably a lethal allele.

Detailed explanation-3: -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-4: -Listen to pronunciation. (HEH-teh-roh-ZY-gus JEE-noh-tipe) The presence of two different alleles at a particular gene locus. A heterozygous genotype may include one normal allele and one mutated allele or two different mutated alleles (compound heterozygote).

Detailed explanation-5: -If an organism has two copies of the same allele, for example AA or aa, it is homozygous for that trait. If the organism has one copy of two different alleles, for example Aa, it is heterozygous.