Mendel’s Law of Segregation

Mendel’s Law of Segregation

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Hi everyone, and welcome to Biology Professor. Today, we’re talking about the Law of Segregation. Now the Law of Segregation is one of the laws
of Mendelian Inheritance. These talk about inheritance of biological
features, which we now call genes. And the inheritance of genes follows three
Laws for the pattern of biological inheritance. These laws were first proposed by Gregor Mendel
in the 1860’s. He was working with pea plants. And it was his work with pea plants that allowed
him to elucidate three different laws of inheritance. These are the Law of Segregation, which is
what we are talking about today, also the Law of Independent Assortment and the Law
of Dominance. If you are interested in learning more about
these other two Laws, see my videos on those topics. But now for the Law of Segregation. It deals with gamete formation. Remember that gametes refer to the cells produced
by parents that later unite to form offspring. In humans, these are sperm cells from the
father and egg cells from the mother. And when sperm cells and egg cells are made,
you have alleles for each genes, remember that alleles are just alternative forms of
a gene, so in a plant you may have a gene for flower color with one allele from the
mother and one allele from the father. Perhaps purple flowers from the mother, white
flowers from the father. That’s an example of two different alleles,
two different alternative forms for the same gene, flower color. Now, during gamete formation, alleles for
each gene segregate from each other. This is just another way of saying that they
separate from each other in some way. This means that each gamete carries only one
allele per gene. So, for example, if we have a man here – remember
that humans are diploid, so they have two copies of each chromosome, that’s why we call
it 2n – so here we have our little man, he is heterozygous – remember that heterozygous
means having two different alleles for a gene, so in this example, with a man who has a dominant
allele and a recessive allele that he got from his parents, and in gamete formation,
each gamete will have one of those alleles, so either the dominant one or the recessive
one. Of course, if this man had been homozygous,
meaning having two identical copies of an allele, every single one of his gametes would
have that allele. So the gametes are 1n, or haploid. This is because they only have one set of
chromosomes. So this is what the Law of Segregation says,
and when these alleles segregate from each other, it’s happening during the process known
as meiosis. And then once the gametes have been formed
during the process of meiosis, they will then randomly unite
in the process of fertilization. And this is where a lot of our genetic variety comes from. The fact that the alleles segregate from each other, that the gametes can have different combination of what the parent has, and the fact that you have one random sperm uniting with one random egg, this results in a lot
of potential diversity. This is why no two people are alike, no two siblings are alike. And it all has to do with the Law of Segregation,
thanks for watching. Remember my other two videos on the Law of
Independent Assortment and the Law of Dominance if you are interested in learning more about
those. And we will see you here at Biology Professor
next time.

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