Homozygous – Class 12 | Chapter – 5 | Biology Short Notes Series PDF

Homozygous: Homozygous refers to having inherited the same versions (alleles) of a genomic marker from each biological parent. Thus, an individual who is homozygous for a genomic marker has two identical versions of that marker. By contrast, an individual who is heterozygous for a marker has two different versions of that marker.


Important Points of Homozygous

  • It has two same copies of the same allele coding for a particular trait.
  • Contains only one type of allele, either dominant or recessive.
  • Self-fertilization results in the repetition of the same traits over generations.
  • Only one type of gamete is produced.
  • It can be either homozygous dominant or homozygous recessive.

Examples of Homozygous

  • Eye color: The brown eye color allele is dominant over the blue eye allele. You can have brown eyes whether you’re homozygous (two alleles for brown eyes) or heterozygous (one for brown and one for blue). This is unlike the allele for blue eyes, which is recessive. You need two identical blue eye alleles in order to have blue eyes.
  • Freckles: Freckles are tiny brown spots on the skin. They’re made of melanin, the pigment that gives color to your skin and hair. The MC1R gene controls freckles. The trait is also dominant. If you don’t have freckles, it means you’re homozygous for a recessive version that doesn’t cause them.
  • Hair color: Red hair is a recessive trait. A person who is heterozygous for red hair has one allele for a dominant trait, like brown hair, and one allele for red hair. They can pass the red hair allele to their future children. If the child inherits the same allele from the other parent, they’ll be homozygous and have red hair.

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By Team Learning Mantras