Welcome to another new day for Biology Tips Daily, offering tips and tricks to help you ease into the biology mastery.
Today's topic is to answer one question: Segregation and independent assortment, what's a big deal?
The big deal is that one process guarantees that each gamete (sperm or egg) gets a copy of each kind of chromosome and the other insures that each gamete is unique, sometimes never having been seen before in the history of life. Big difference...big deal.
Chromosomes carry DNA, the genetic material passed on from generation to generation. You have two copies of each kind of chromosome. Each pair is called homologous. One copy of each kind of chromosome (one homolog) came from each of your biological parents (thanks mom! thanks dad!). In this picture, homologous pairs are the same color. In your cells, homologous chromosomes are the same size and shape and they have the same kinds of genes (except for the sex chromosomes).
During meiosis, the process by which gametes are formed, homologous chromosomes get separated from one another and placed in different gametes. So each gamete has only one copy of each kind of chromosome. The process whereby the homologous chromosomes separate from each other is called segregation. Segregation insures that when you put sperm and eggs together, the zygote (fertilized egg) will have two copies of each kind of chromosome, just like each of the parents.
In this picture, a cell is going through meiosis. There are two pairs of homologous chromosomes, a larger pair at the top and a slightly smaller pair with red tip at the bottom. Let's say that within a pair, the green chromosome came from mom and the yellow came from dad.
Since the homologs are being separated from one another and moving toward the far ends of the cell, when this cell finishes dividing (indicated by the "pinch" in the middle of the cell), the daughter cells will have one copy of each kind of chromosome. The homologous chromosomes will be segregated from each other in different cells.
Now that segregation is clear, let's tackle independent assortment. Independent assortment means that what happens during segregation within one pair of homologous chromosomes does not affect the segregation of other pairs of homologous chromosomes.
If you consult our picture of the dividing cell, we note that a yellow and a green chromosome are going into each of the two new cells. But according to the principle of independent assortment, the two greens can go into the same cell or the two yellows can go into the same cell or a green and a yellow can go into the same cell. So three different genetic kinds of gametes can result from independent assortment.
Segregation insures the right number of chromosomes per gamete and independent assortment contributes to the uniqueness of each gamete. There you go.
Until then, stay tuned for more biology tips.
Seize the Day!
Dr. Wayne Huang
"The Rapid Learning Coach"
BioTips@RapidLearningCener.com
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