Genetic meterial of shermy's spermies

1. Sep 16, 2004

Jamez

Genetic material of shermy's spermies

During one of our usual "relief-teacher-day" debates in Geometry and Trigonometry, somehow we got into a discussion about the genetic material of sperm. Do all spermies from Shermy have the same genetic material as his other spermies? or does each sperm contain different combinations of genetic material?

Last edited: Sep 16, 2004
2. Sep 16, 2004

Monique

Staff Emeritus
They contain different genetic material, otherwise all siblings would look alike

What happens is that you have two chromosomes of each kind, so you can either inherit one or the other. There is also a process where pieces of the two chromosomes get interchanged, recombined, which causes additional variation.

3. Sep 16, 2004

Brennen

so all female eggs have different chromosomal make-up, and all sperm have different chromosomal make-up?

4. Sep 16, 2004

Jamez

he he, that was my argument

Two chromosomes of each kind? Do you mean chromatids? So each chromosome is a pair of different chromatids? These chromatids are not exactly the same as the other one of its pair right?
Someone said they were exactly the same, therefor the genetic meterial of all of the sperm is the same for that person.

5. Sep 16, 2004

Moonbear

Staff Emeritus
You have it right, the chromatids are not identical (one came from mom and the other from dad). To start out, you have 23 pairs of chromosomes, and half of those chromosomes wind up in the sperm, but as long as it's one each of those 23, they can be in any combination (let's say you called each half A and B...you could get 1A, 2B, 3B, 4A... or you could get 1B, 2B, 3A, 4A... or you could get 1A, 2A, 3A, 4B... etc...). And, as Monique pointed out, there are also ways that the two chromatids can swap genetic material, so part of 1A winds up on 1B and vice versa. This makes for a lot of potential variation.

And, Brennen, yes, the same is true for eggs.

6. Sep 17, 2004

Monique

Staff Emeritus
No, generally chromatids are identical: they are the two daughter strands of a duplicated chromosome joined at the centromere during mitosis and meiosis.

Recombination takes place only during meiosis I between NON-sister chromatids.

7. Sep 17, 2004

Moonbear

Staff Emeritus
D'oh! *smacks self on forehead* Sorry about that...what the heck was I thinking when I replied yesterday? I should answer questions at night, when I'm awake, not in the morning when I'm still clinging to a cup of coffee. Jamez, if I've confused you further, just ignore my previous reply.

8. Sep 17, 2004

Monique

Staff Emeritus
For clarification, normally a chromosome is a long string: |
You have two chromosomes 1: | |, two chromosomes 2: | |, etc

The chromosomes in the pair carry the same genes, but are slightly different (the gene on one will code for blue eyes, the gene on the other will code for green eyes). One is maternal (from the mother), the other paternal (from the father).

What happens during meiosis is that the DNA duplicates, but remain attached in the middle (at the centromere), thus you get two chr. 1: X X, two chr. 2: X X, etc.

First all the chromosome pairs will allign together in a plane: this is when recombination can take place, since they are in close proximity to each other. The chromosomes get pulled apart and end up in separate cells. So now there is only one chr. 1: X, and one chr.2: X, etc.

Then the two chromatids get pulled apart and end up in separate cells, now you've got the traditional chromosomes back again: one chr. 1: |, one chr. 2: |, etc. (the cell is haploid, ready for fertilization).