Chromosome behaviour and Variability

[sidzeman]

Hey could someone please explain how chromosomes in meiosis lead to biodiversity?
I get confused on the exact details of the law of independent assortment and random segregation

[pikachu975]

Hey could someone please explain how chromosomes in meiosis lead to biodiversity?
I get confused on the exact details of the law of independent assortment and random segregation

Crossing Over;
In the prophase I, chromosomes exchange genetic material (genes) which leads to variation in each chromosome.

Segregation of Chromosomes:
At both Anaphase I and II, homologous pairs of chromosomes split and segregate into the two halves of the cell, ready to be split in the telophase. This random segregation leads to variation as the haploid cells can get any combination of chromosomes.

Independent Assortment:
This also happens with segregation where it just means that genes assort randomly into each new cell, not together. E.g. if your mum has blue eyes and blue hair and your dad has brown eyes and brown hair, then you CAN get blue eyes and brown hair. If this law was not true then the blue eyes and blue hair gene would assort TOGETHER and it means there would be no variation.

Biodiversity:
These all lead to biodiversity because the genes of the offspring have changed. This means with polypeptide synthesis (Transcription and Translation), different phenotypes will be produced in the offspring therefore causing biodiversity and a varied gene pool.

[vox nihili]

Crossing Over;
In the prophase I, chromosomes exchange genetic material (genes) which leads to variation in each chromosome.

Segregation of Chromosomes:
At both Anaphase I and II, homologous pairs of chromosomes split and segregate into the two halves of the cell, ready to be split in the telophase. This random segregation leads to variation as the haploid cells can get any combination of chromosomes.

Independent Assortment:
This also happens with segregation where it just means that genes assort randomly into each new cell, not together. E.g. if your mum has blue eyes and blue hair and your dad has brown eyes and brown hair, then you CAN get blue eyes and brown hair. If this law was not true then the blue eyes and blue hair gene would assort TOGETHER and it means there would be no variation.

Biodiversity:
These all lead to biodiversity because the genes of the offspring have changed. This means with polypeptide synthesis (Transcription and Translation), different phenotypes will be produced in the offspring therefore causing biodiversity and a varied gene pool.

Just a minor point. Independent assortment and random segregation of chromosomes are effectively the same thing

[sidzeman]

Yea thats a major source of my confusion - whats the difference between the 2
I know one of them is that when chromosomes split from the tetrad and line up to go into separate cells (this happens at metaphase 1 and 2 right?)  they do so randomly - so both paternal chromosomes wont be in one half and maternal in the other - it can be random
Is this random segregation? I'm not sure I understand independent assortment then

[pikachu975]

Yea thats a major source of my confusion - whats the difference between the 2
I know one of them is that when chromosomes split from the tetrad and line up to go into separate cells (this happens at metaphase 1 and 2 right?)  they do so randomly - so both paternal chromosomes wont be in one half and maternal in the other - it can be random
Is this random segregation? I'm not sure I understand independent assortment then

Independent assortment is like two genes aren't always moving together, they can go to different sides of the cell. E.g. blue hair colour allele doesn't always go with blue eye colour. This is because of random segregation. Here's an excerpt from google:

"the principle, originated by Gregor Mendel, stating that when two or more characteristics are inherited, individual hereditary factors [GENES] assort independently during gamete production, giving different traits an equal opportunity of occurring together"

For example in punnett squares, you can cross Yy and Yy to get Yy, Yy, YY, yy for example Y for yellow hair and y for pink. For eye colour you can cross Bb and Bb to get BB, bb, Bb, Bb where B is brown and b is blue.

This shows that you can get a combination of Yellow hair and Brown eyes, Yellow hair and blue eyes, Pink hair and brown eyes, and Pink hair and blue eyes. This is basically saying that the alleles for hair colour (For example) don't always assort WITH the alleles for eye colour, they assort independently. If there was no independent assortment then there would just be set combinations; no variation: Yellow hair and brown eyes OR pink hair and blue eyes, for example, with no other combination.

[vox nihili]

Yea thats a major source of my confusion - whats the difference between the 2
I know one of them is that when chromosomes split from the tetrad and line up to go into separate cells (this happens at metaphase 1 and 2 right?)  they do so randomly - so both paternal chromosomes wont be in one half and maternal in the other - it can be random
Is this random segregation? I'm not sure I understand independent assortment then

Good on you for having a crack at answering your own question first, we love to see that and you get a lot more out of it

They not really two different things. They describe different parts of the same concept.

Random segregation means that where the chromosomes end up is completely random. Whether they end up in cell A or B is simply by luck, nothing else.
Independent assortment on the other hand means that each chromosome does its own thing. In other words, the direction that chromosome 1 goes does not affect the direction that chromosome 2 goes etc etc.

[sidzeman]

Sorry guys I still seem to be struggling. So do both principles occur at the same phase of meiosis - during anaphase 1 and 2?

[pikachu975]

Sorry guys I still seem to be struggling. So do both principles occur at the same phase of meiosis - during anaphase 1 and 2?

Yep. Independent assortment isn't really a process it's just a rule that describes segregation (saying that genes assort independently).

[sidzeman]

alright thank you guys so much for all your help

[LetsBeCats]

If you still needed another one random selection of gametes is also another our teacher noted as there are heaps of egg and sperm but only certain ones meet