Heterozygous | Definition & Examples


Heterozygous Definition:

Heterozygous Definition Biology: An individual if consists of two distinct alleles of the particular genotype. Pair of genes, called alleles, and each allele is located in the locus (specific position) on a chromosome. If the two alleles are different from each other at a locus, they are said to heterozygous. Like the word �hetero�, it means to do with things which are different, especially for genes. The alleles are unlike at some points in it. The alleles describe the specific genotype of a gene. In other words, alleles have two different types of genes which control a particular characteristic.

For example, if an offspring child receives the allele of brown eyes from his father, and the allele of grey eyes from his mother; that means the offspring is heterozygous for the color of eyes.


Examples of Heterozygous:

  • Heterozygous Individuals & Sickle-Cell Trait:

Sickle Cell Trait (SCT) does not mean disease. Sickle Cell Trait (SCT) means that an offspring has inherited the sickle cell genes from one of his parent father or mother. A person who has SCT generally not has any symptoms of sickle cell disease (SCD) and lives a normal life. In this pattern, a person has one abnormal allele of heterozygous. But he does show any symptom of Sickle Cell Disease (SCD). Sickle Cell Trait (SCT) generate both normal and abnormal hemoglobin. Hemoglobin is said to be two Codominant alleles made in order to the actual concentration of hemoglobin. Sickle Cell Disease is said to be blood disorder which causes blood cells to make a sickle shape, because of low oxygen tension. Sickle Cell Disease (SCD) also secures blood cells from �malaria�. So, a person who has Sickle Cell Trait (heterozygous) has the advantage of stay secure from malaria.


  • Curly Hair:

The hair type as curly or straight controlled by two types of alleles. If alleles of both parents are for curly hair (homozygous), the offspring has allele of curly hairs. If both alleles are for straight hair, the offspring is homozygous straight hair. But in some cases, one individual has allele of curly hair, and others have allele of straight hair. In this pattern, the offspring is heterozygous which blends the effect alleles of both the curly hair and straight hair.


  • Blood Type:

Blood type is a common example of it. Human blood groups are controlled by multiple alleles. There are three different alleles for blood groups (A, B, and O). A and B blood type is dominant over O. If a parent has allele of Blood type �A�, and another parent has Blood type �B�, the offspring child may have heterozygous of both alleles as blood type �AB�.


Heterozygous Alleles:

Homozygous is said to be when two individuals have both same copies of alleles, may be dominant both or recessive both. When organisms both alleles are different from a gene. In this� Alleles, there are two different alleles which occupied by a particular gene. Alleles are inherited by sexual reproduction, in the resulting offspring receives half of the chromosome from father and a half from the mother. In this, offspring receives different effects of chromosomes from both father and mother.


Heterozygous Genotype:

The set of genes in our DNA which is responsible for a specific trait is known as genotype. An individual or organism has the genetic constitution of a cell. By the expressed features, the genotype is distinct of every individual. A genotype of a person is related to the genetic makeup of the parent (father). It contains all genes pertain to the specific gene of a parent.

The genotypes of individuals are the chemical composition of its DNA, which helps to raises the observable traits of an individual. Genotypes contain all of the nucleic acids which are present in a DNA molecule for a particular trait. The physical appearance is the result of the combination of proteins created by the DNA. Genotypes have different forms or alleles. Mutation of DNA produces different alleles and may cause detrimental or beneficial changes. In bacteria, the DNA has only one allele for each genotype. There are two alleles present in sexually reproducing organisms, which may have a complex interaction with genes and other genes. In these alleles, a mutation can occur, and new combinations can produce during meiosis.


Heterozygous Dominant:

An individual is homozygous if the individual has two same copies of allele for a gene. An individual may be dominant homozygous if it has two copies of the same allele for a gene. And an individual said to be recessive homozygous if it has the same copies of the recessive allele for a gene. An individual is said to be Heterozygous if it has two different alleles of a gene. For instance, the pea plant may have red flowers and white flowers.

If the offspring has red flowers, it means that the plant is dominant homozygous (red-red), or it will be dominant heterozygous if pea flower has a red-white plant.

Heterozygous Recessive:

An individual is said to be heterozygous if it must match with another homozygous recessive to form specific hereditary trait. For example, in human eyes, the genotype is the same as phenotype. If one parent has homozygous dominant brown eyes and other has homozygous recessive blue eyes, the offspring will have heterozygus allele of brown eyes.