Question

Explain and give an example of what an allele is, how alleles are related to an individual's genotype and phenotype, and how alleles are related to genes, DNA, and chromosomes. Please include in your explanation what it means to be heterozygous vs. homozygous, dominant vs. recessive, and give an example of a gene that exhibits incomplete dominance and explain how that impacts the pattern of inheritance.

Answer 1

Allele is a variant of a gene. Humans have two alleles of each gene inherited from parents (one from paternal and another from maternal side). Combination of alleles give raise to different genotypes and phenotypes. (phenotypes are not always observable.) DNA carries the genes. Chromosomes are condensed form of DNA. If both the alleles are of same type (either dominant or recessive), then it is called homozygous. If the alleles are different (one allele is dominant and other is recessive) then it is called heterozygous. In the 2 alleles, if one allele is able to mask the effect of another allele, then the first allele is dominant over the second allele. The second allele is recessive over the first allele. Incomplete dominance is where the dominant allele is not able to completely dominate ver the recessive allele. As a result an intermediate phenotype is observed which is not present in homozygous dominant or homozygous recessive combination. Example is snapdragon flowers. The dominant allele shows pink flowers. recessive alleles make white flowers. If the plant is heterozygous for the alleles, then an intermediate color pink flowers are produced.