Molecular Genetics

Difference Between Homozygous & Heterozygous

The human DNA is a complex aspect of living organisms. Understanding the difference between homozygous and heterozygous is an important part of the study of DNA and genetics. Students can learn more about homozygous and heterozygous here. Most noteworthy, students will understand the difference between homozygous and heterozygous here.

difference between homozygous and heterozygous

What is the Difference Between Homozygous and Heterozygous?

Homozygous, simply speaking, means having identical alleles for a single trait. Furthermore, alleles are known to exist in various different forms.

The diploid organisms almost always have two alleles for a particular trait. Homozygous means a particular r gene that has alleles of an identical nature on both the homologous chromosomes.

The situation of heterozygous stands in contrast to that of homozygous. This is because, in heterozygous inheritance, the genes come from two cells which are parent cells.

When it comes to diploid organisms, heterozygous happens to be an organism that has two different alleles for a certain trait. This article discusses the difference between homozygous and heterozygous in detail.

Chromosomes

Humans are certainly diploid organisms. What this means is that each cell contains two copies of each and every chromosome. For the purpose of conservation of diploidy, the sperm and egg cells each contribute only one copy of each chromosome at the time of conception.

This causes the offspring to receive the full diploid complement. Meiosis is the process by which sperm and egg cells facilitate the splitting of chromosomal copies in order to become haploid.

Homozygous and Heterozygous

When we talk about genetic traits, experts look at genes. Furthermore, they also look at the locus where that trait or gene encodes on the chromosome. Also, humans certainly have two copies of each chromosome. Similarly, they also possess copies of each gene and locus on such chromosomes.

Allele refers to each of these trait-encoding genes (or loci). In case the alleles match, for that particular trait the person is homozygous. In contrast, if the alleles are different, then for that particular trait the person is heterozygous.

Dominant and Recessive Inheritance

For this type of inheritance, one must look at alleles using letters where a capital letter shows a dominant allele, and a lowercase letter is representative of a recessive allele: AA, Aa, and aa.

Examples of dominant traits can be like the ability to roll the tongue or have a genetic likelihood of developing Huntington’s disease. Moreover, such traits only require one dominant allele for the purpose of expression.

This means that people or organisms with homozygous dominant alleles (AA) and also the heterozygous alleles (Aa) express such traits. However, people with homozygous recessive alleles (aa) certainly do not express such traits.

Recessive traits, in contrast, are like having straight thumbs or cystic fibrosis. Furthermore, such recessive traits require two recessive alleles for the purpose of expression.

This means that only people who are characterized by the homozygous recessive alleles (aa) express the trait. People with homozygous dominant alleles (AA) will not carry the trait or express it. Finally, there is no expression of the trait from individuals with heterozygous alleles (Aa) but they happen to be carriers for it.

Solved Questions on Homozygous and Heterozygous

Q1 Which of the following statements with regards to homozygous and heterozygous is wrong?

A. Homozygous means having identical alleles for a single trait
B. In heterozygous inheritance, the genes come from two cells which are parent cells
C. Humans are not diploid organisms
D. The diploid organisms almost always have two alleles for a particular trait

A1 The correct option is C., which is “humans are not diploid organisms.” This is because the correct statement is “humans are certainly diploid organisms.” The other three options are definitely true with regards to homozygous and heterozygous.

Share with friends
Customize your course in 30 seconds

Which class are you in?

5th
6th
7th
8th
9th
10th
11th
12th
Get ready for all-new Live Classes!
Now learn Live with India's best teachers. Join courses with the best schedule and enjoy fun and interactive classes.
tutor
tutor
Ashhar Firdausi
IIT Roorkee
Biology
tutor
tutor
Dr. Nazma Shaik
VTU
Chemistry
tutor
tutor
Gaurav Tiwari
APJAKTU
Physics
Get Started
Customize your course in 30 seconds

Which class are you in?

No thanks.