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

Heterozygous: Heterozygous is a state of inheriting various forms of a specific gene from each of the parents. Various forms correspond to saying that there are fragments of the genes wherein the sequence differs, which can range from trivial segments of the gene to the most important sections of the gene.



Important Points of Heterozygous

  • It contains two different copies of alleles coding for a particular trait.
  • Contains different alleles for a trait. Both dominant and recessive.
  • Self-fertilization results in different combination of traits over the next generations.
  • Two types of gametes are produced in this.
  • Heterozygous alleles can show complete dominance, codominance or incomplete dominance

Example of Heterozygous

An example of a heterozygous condition is inheriting different genes for eye colour from both biological parents. If there are two different versions, it is a heterozygous genotype for that particular gene. Another example is heterozygous for the colour of hair, which corresponds to having one allele for brown hair and the other alleles for red hair. The equation between both alleles has an influence on which characteristic gets suppressed and which gets expressed. It is also an indicator of what traits are carried.

Heterozygous dominant and Heterozygous recessive

In the event where an allele is faulty or mutated, a disease can be inherited by the offspring even if parents do not experience any sign of it. In heterozygosity, there are many forms of this:

  • Alleles are heterozygous recessive: Mutated alleles would be recessive and hence suppressed and not expressed. The person, in this case, would be a carrier.
  • Alleles are heterozygous dominant: Mutated alleles would be dominant, and hence the individual may or may not get affected by it.

Diseases of Heterozygous

  • Familial hypercholesterolemia (FH): An inherited condition, FH is distinguished by high levels of cholesterol, to be precise, the LDLs (low-density lipoproteins). It is seen to affect 1 in 500 individuals and is a common disorder.
  • Sickle cell: This characteristic can take place in a heterozygous environment. Here, the allele for sickle-cell is an advantage as it safeguards an individual against the condition of Malaria, however, does not cause them to fall sick with sickle cell. This, as discussed, is a heterozygote advantage and is suggested as the reason that character is seen in the population of humans.
  • Huntington’s disease: This is a condition that is inherited, leading to the fatality of the brain cells. The condition is a result of the dominant mutation in any one or both the alleles for a gene, referred to as the Huntingtin.

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By Team Learning Mantras