We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.
Biology

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

What Is a Heterozygote?

By Kirsten C. Tynan
Updated: May 23, 2024
Views: 13,297
References
Share

A heterozygote is an organism that has two different forms of the same gene, with one being the dominant form and the other the recessive form. Genes are functional units that transmit hereditary information when organisms reproduce. They occur in pairs and have different forms, one dominant form and at least one recessive form, called alleles. Alleles can pair off in various ways such as one dominant with one recessive allele, two recessive alleles together, or two dominant alleles together. Dissimilar alleles occur in a heterozygote while either of the two similar pairs can occur in a homozygote.

Dominance is the ability of an allele to express its phenotype, or observable characteristics defined by its genetic code, while another allele’s phenotype is unexpressed. A common example of this is eye color in humans. Brown is a dominant trait while blue is recessive. If a person has one allele for brown eye color and one for blue, the person’s eyes will be brown because brown is dominant. Such a person is said to be heterozygous for eye color.

When a heterozygote exhibits evolutionary fitness greater than that of either homozygote, this phenomenon is known as a heterozygote advantage, or simply overdominance. Many experts think that evolutionary disadvantages can be preserved in the gene pool through this phenomenon. If having two copies of some allele is an evolutionary disadvantage, it would ordinarily be expected to disappear from the gene pool through natural selection. It can be preserved, however, if having one copy of it paired with another allele poses an evolutionary advantage.

The standard textbook example of this is sickle cell anemia. The recessive allele of a particular human gene causes sickle cell anemia, which is disadvantageous to an organism’s prospects for survival and reproduction. When coupled with another allele of the same gene, however, the gene pair confers on the organism resistance to a deadly disease called malaria. Such resistance can greatly improve an individual’s prospects for survival and reproduction in areas of the world where malaria is a concern.

Many other examples of heterozygote advantage are thought to exist, but other explanations for them have yet to be ruled out. Certain rats, for example, exhibit an advantage of pesticide resistance that appears to be related to a disadvantage of deficiency in vitamin K levels. Another example is a possible heterozygote advantage in female pigeons of lower microbial infection rates and higher rates of egg hatching.

The phenomenon opposite heterozygote advantage is, of course, known as heterozygote disadvantage, or underdominance. A particular species of grass has been found that is a possible example of underdominance. Heterozygous members of a natural population of this species have been found to produce fewer viable seeds than homozygotes of the same species.

Share
InfoBloom is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Link to Sources
Discussion Comments
Share
https://www.infobloom.com/what-is-a-heterozygote.htm
Copy this link
InfoBloom, in your inbox

Our latest articles, guides, and more, delivered daily.

InfoBloom, in your inbox

Our latest articles, guides, and more, delivered daily.