Question

Distinguish between homozygosity and heterozygosity.

Short answer

Answer: The main differences between homozygosity and heterozygosity in genetics are: 1. Homozygosity involves inheriting two identical alleles of a given gene, while heterozygosity involves inheriting two different alleles of a given gene. 2. Homozygous individuals can be either dominant or recessive, whereas heterozygous individuals have one dominant and one recessive allele. 3. In a homozygous individual, the phenotype (physical appearance) is determined by the nature of the alleles (dominant or recessive), while in a heterozygous individual, the phenotype is determined by the dominant allele.

Step-by-step solution

Define Homozygosity

Homozygosity occurs when an individual inherits the same allele for a specific gene from both of their parents. In other words, homozygosity is when both homologous chromosomes carry the same allele of a given gene. These individuals are called homozygous for that particular gene, and the alleles can either be dominant or recessive.

Define Heterozygosity

Heterozygosity occurs when an individual inherits different alleles for a specific gene from each of their parents. These individuals are called heterozygous for that particular gene. Heterozygosity reflects the presence of two different alleles of a given gene on a pair of homologous chromosomes.

Examples

In order to better understand homozygosity and heterozygosity, consider the gene responsible for eye color. Using the simplified example where the gene has only two alleles, the dominant allele B (brown eyes) and the recessive allele b (blue eyes). A homozygous individual would have either two dominant alleles (BB) or two recessive alleles (bb). In the first case, the individual would have brown eyes, while in the second case, the individual would have blue eyes. A heterozygous individual would have one dominant allele and one recessive allele (Bb). In this case, since the dominant allele masks the effect of the recessive allele, the person would have brown eyes.

Differences between Homozygosity and Heterozygosity

1. Homozygosity involves two identical alleles of a given gene, while heterozygosity involves two different alleles of a given gene. 2. Homozygous individuals can be either dominant or recessive, whereas heterozygous individuals have one dominant and one recessive allele. 3. In a homozygous individual, the phenotype (physical appearance) is determined by the nature of the alleles (dominant or recessive), while in a heterozygous individual, the phenotype is determined by the dominant allele.