A monohybrid cross involves mating two parents with different alleles for a single trait, resulting in heterozygous offspring. An example is two pea pods with green and blue coloration alleles. The dominant green allele is expressed as “G” and the recessive blue allele as “g”. Offspring from a homozygous dominant and homozygous recessive parent will be heterozygous and green. Breeding two heterozygous offspring results in four possible outcomes, including a 25% chance of blue offspring. Monohybrid crosses are a basic way to learn genetics.
Monohybrid cross is a term for a mating in which two members of a parent generation share a genetic trait that is influenced by two alleles or DNA sequences. These parents are typically both heterozygous, and how the trait will be expressed in members of a generation of offspring can be expressed through a simple analysis of how the alleles can mate. The two alleles usually indicate dominant and recessive properties of this single trait. A monohybrid cross compares only a single trait and the alleles involved and can typically begin with a homozygous mating, which gives way to heterozygous offspring.
The easiest way to explain a monohybrid cross scenario is with a fairly simple example. It begins with two pea pods, one green and one blue, determined by a chromosome representing the coloration trait. The green allele is dominant and expressed as “G”, while the blue allele is recessive and expressed as “g”. These two parent plants are homozygous diploid organisms, meaning that each has two alleles on the chromosome indicating coloration. Homozygous means that both of these alleles are the same and diploid indicates that there are two alleles to establish this trait.
One is purely dominant green, expressed as “GG”, each “G” represents an allele; the other is a fully blue recessive, “gg,” meaning this parent is actually blue in color. Since each offspring they have gets one allele from each parent, all of their offspring would have staining chromosomes consisting of “Gg”. In this mating, all offspring are green, as the dominant allele is present, although they still contain the recessive possibility for blue coloration.
These resulting generations are called heterozygous as their alleles are not the same, unlike the parent generation. If two heterozygous offspring are then bred together, the resulting possibilities constitute a monohybrid cross. Since the two parents in a second breeding would both be “Gg”, the possibilities for the coloration trait in the offspring are easy to predict. There are four possible results: “GG”, “Gg”, “Gg” and “gg”.
Using this type of monohybrid crossing experiment, it becomes apparent how a recessive trait can continue to exist even when it is not visible. While the odds are certainly against it, there is a 25% chance from this type of mating that the offspring will be blue in color and become homozygous regarding this trait. The offspring of this prospective parent would be more likely to be blue when mated to a heterozygous mate, although with a homozygous dominant parent, again “GG”, the offspring would again be heterozygous. A monohybrid cross is often the easiest way to start learning basic genetics, as it only compares a single trait, unlike a dihybrid cross which considers two traits.
Protect your devices with Threat Protection by NordVPN
