Heterozygous vs. Homozygous: What’s the Difference? — Passage
In genetics, the terms heterozygous and homozygous describe the combinations of alleles an organism inherits from its parents. Alleles are different forms of the same gene, and they determine an organism’s traits, like eye color or blood type. Each person gets one allele from each parent, forming a pair for every gene.
A person is homozygous if the two alleles for a gene are the same. These can be homozygous dominant (like BB) or homozygous recessive (like bb). In both cases, the same version of the gene is inherited from each parent. If the gene is dominant, the trait will be visible even with just one copy. If the gene is recessive, the trait only appears when both alleles are recessive.
A person is heterozygous if the two alleles are different, such as Bb. In this case, the dominant allele will mask the recessive allele, so the dominant trait is the one that shows up. Even though the recessive gene is present, it doesn’t affect the outward trait unless paired with another recessive allele.
Scientists use Punnett squares to predict whether offspring will be homozygous or heterozygous for a trait. For example, if one parent has two dominant alleles (BB) and the other has two recessive alleles (bb), all their children will be heterozygous (Bb). This kind of inheritance explains why traits sometimes “skip” a generation.
Understanding the difference between heterozygous and homozygous is important in genetics, medicine, and breeding. Some genetic disorders only occur in homozygous individuals. In farming, breeders choose between homozygous and heterozygous plants and animals to get the traits they want.
Fun Fact: Pea plants were the first organisms used to study heterozygous and homozygous traits—by a monk named Gregor Mendel in the 1800s!
What do heterozygous and homozygous describe?
Types of cellsBody systemsCombinations of allelesTypes of traitsWhat does homozygous mean?
Two different allelesOne allele onlyTwo identical allelesNo alleles presentWhich is a heterozygous genotype?
BBBbbbBBbbWhat kind of allele is masked in a heterozygous pair?
DominantInheritedRecessiveNeutralWhat will all offspring be if one parent is BB and the other is bb?
bbBBBbbB or BBWhy can a recessive trait “skip” a generation?
It is forgottenIt needs two recessive allelesIt’s weakerIt disappears randomlyWhat is the main idea of the passage?
Heterozygous traits are rareAlleles are always recessiveDominant traits are unhealthyHeterozygous and homozygous describe allele pairsHow is this knowledge used in farming?
To grow only recessive plantsTo stop traits from changingTo select traits in plants and animalsTo change the color of cropsRelated Content
