In this video, we're going to introduce Gregor Mendel's Law of Segregation. The law of segregation basically says that during gamete formation or during meiosis, two alleles of the same gene are going to segregate or separate from each other and end up in different gametes. In other words, the law of segregation states that gametes are haploid, meaning they will only receive one copy of a gene or allele.
Let's consider our example of the law of segregation. Notice that at the top, we have a homozygous dominant cell that has two dominant alleles. We have a heterozygous cell that has one dominant allele and one recessive allele. Lastly, there is a homozygous recessive cell that has two recessive alleles. Before meiosis can take place, the DNA needs to be replicated. After DNA replication, we have duplicated chromosomes, meaning we have an extra copy of each of these alleles. At this stage, before meiosis begins, there are a total of four alleles. After meiosis I and meiosis II, each of these four alleles segregates and separates independently, ending up in gametes so that each gamete only receives one copy of the allele for that particular gene.
The same happens in the heterozygous cell, where it undergoes DNA replication to produce an extra copy of each of the alleles. Ultimately, they will all segregate or separate from one another by the law of segregation, ensuring that each of the gametes only receives one copy of the alleles.
Similarly, for the homozygous recessive, just before meiosis begins, DNA replication occurs where the chromosomes replicate or duplicate, and there will be an extra copy of each of these alleles. These alleles once again segregate and separate from one another so that each of the gametes receives only one copy of the allele, making all these gametes haploid.
The law of segregation was previously discussed when we talked about meiosis in our earlier lesson videos. Gregor Mendel, through his study of pea plants, discovered the law of segregation. This concludes our introduction to the law of segregation. We'll practice applying these concepts as we progress in our course and then discuss the law of independent assortment. I'll see you all in our next video.