What is a heterozygous gene.

Difference between homozygous and heterozygous

We will deal with the difference between homozygous and heterozygous in this article. The required basic knowledge is first conveyed and then the difference between these two terms is discussed. This article belongs to our biology / genetics section.

In order to be able to correctly classify the terms homozygous and heterozygous, one should know a few basic terms. These usually appear when explaining the difference between these two terms and should therefore be understood.

Important basic terms:

  • Homologous chromosomes: Chromosomes are the carriers of the genetic make-up. They consist of a thread of DNA and proteins. The term homologous chromosome describes a chromosome that corresponds to another chromosome in terms of shape and sequence of genes.
  • gene: This is a section of the DNA molecule that contains the information for the synthesis of a protein.
  • A.llele: Alleles or allelic genes are two different states of a gene that occupy the same place on homologous chromosomes.
  • haploid and diploid: Body cells of a sexually reproducing organism have two sets of chromosomes and are therefore referred to as diploid (2n). A cell therefore contains a double set of chromosomes from maternal and paternal genetic makeup. Germ cells (egg cells and sperm), on the other hand, only have a single set of chromosomes and are therefore haploid (1n). However, there are also living things - especially plants - that are even triploid or polyploid.
  • Dominant and recessive: In the case of dominant recessive inheritance, one allele prevails over another allele in the expression of a characteristic. The prevailing allele is referred to as dominant, the other as recessive.

Homozygous and heterozygous

A diploid organism has two copies of each gene that codes for example blood type or hair color, usually one from each parent. If both alleles of an individual are the same for a certain trait, the genetic makeup - based on this trait - is homozygous. If, on the other hand, there are two different alleles, this is referred to as heterozygous.

An example of this are the investigations by Gregor Mendel, which resulted in Mendel's laws. For example, he studies the colors of flowers. If pure red-flowered and pure-blooded white-flowered individuals are crossed, their offspring have inherited a genetic make-up for white (from one parent) and a genetic make-up for red (from the other parent); they are heterozygous. If, in another case, only the color yellow was available as genetic information, then one speaks of homozygous. Reading tip: Mendel's laws.


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