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#Mendel - s First Law: The Law of Segregation - Video - Lesson Transcript

Mendel's Experiments

Austrian monk Gregor Mendel studied pea plant genetics in the 1800s

Gregor Mendel was an Austrian monk who studied pea plant genetics in the 1800s. Mendel's experiments provided quantitative data, which would eventually revolutionize the understanding of the inheritance of traits. Unfortunately for poor Mendel, his findings were largely ignored until 1900, when the observation of meiosis helped scientists realize the significance of Mendel's experiments.

Mendel's laws helped explain chromosome-based inheritance of traits. Mendel is also credited with identifying the concept of dominant and recessive traits. We've already seen how a dominant trait affected Adrian's flying hamster experiment.

Now we're going to examine Mendel's first law of inheritance. also known as Mendel's law of segregation. It states that, ' the alleles of a given locus segregate into separate gametes.'

So let's see how the law of segregation applies to our hamster genetics experiments.

Alleles Associated with Chromosomes

We learned that an animal with a homozygous dominant genotype ('BB') will produce a hamster that is brown. We also know that if we have a heterozygous genotype ('Bb'), we will also produce a hamster that is brown. However, if we have a hamster that has a 'bb' genotype (homozygous recessive ), it will produce a hamster that is white.

Organisms with homozygous dominant or heterozygous genotypes will display the dominant trait

We also know that genes are associated with a specific chromosome. For a flying hamster, we have three different chromosomes. Let's say that we discover that the coat color gene is located on chromosome three.

For instance, in the case of the heterozygous hamster, one of the chromosome threes has the 'B' allele and the other chromosome three has the 'b' allele. To make it a little easier for us to track our chromosomes, let's make this one blue - so 'B' is going to be associated with a blue chromosome. And let's make this one red; 'b' is going to be associated with this red chromosome. I've just arbitrarily picked those colors to make it easier for us to track what those chromosomes are doing.