Understanding Test Cross: Determining Genotypes with Eye Color

TLDR; The video explains the concept of a test cross to determine the genotype of an individual, using eye color as an example.

💡 Understanding Test Cross

The test cross is a specific genetic concept used to determine an individual's genotype by observing the phenotype.

For example, using eye color as a simple way to understand genetics, the concept is explained.

Blue and brown eye colors are used to illustrate the idea of genotypes and phenotypes.

The speaker explains that knowing the genotype of an individual with brown eyes is more challenging compared to someone with blue eyes.

This is where the test cross comes into play to figure out the genotype of the individual with brown eyes.

👁️ The Test Cross Process

The test cross involves crossing an individual with an unknown genotype with another individual with a known genotype.

In the case of eye color, crossing a person with unknown genotype for brown eyes with a person with blue eyes helps determine the potential outcomes of their offspring.

If the individual with brown eyes is homozygous dominant (Big B Big B), all offspring from the cross will have brown eyes.

However, if the individual with brown eyes is heterozygous (Big B little b), the offspring will have a 50% chance of having blue eyes.

🌱 Application in Breeding

The speaker highlights that the test cross is used in breeding for animals and plants but emphasizes that it would never be used for humans.

It is commonly used to determine if a plant or animal is 'pure breeding', meaning they have two copies of the same allele.

This is important for breeding purposes.

📝 Summary of Test Cross

The purpose of a test cross is to determine the genotype of an individual who displays the dominant phenotype.

By crossing with a homozygous recessive individual, it becomes possible to determine whether the individual is homozygous dominant or heterozygous.

If all offspring resemble the parent, it indicates a homozygous dominant genotype.

If 50% of the offspring differ, it suggests that the parent was actually heterozygous.