Hey, would anyone be able to explain to me metaphase I/anaphase I in meiosis - or more specifically just how homologous chromosomes work. I know that when they line up, it's the paternal and maternal copy of the same chromosome lining up, but I don't understand how this fits in with the whole scheme of things because fertilisation happens after this point, right? So how does one cell that is preparing for fertilisation already have the genetic material from both parents?
Thanks!
Hi! This is a really good question!
Homologous chromosomes, as you correctly said, are one copy of each chromosome from the mother, and one copy of each chromosome from the father. They are similar in length but may have different alleles.
In females, meiosis occurs before birth, and in males in continually occurs after puberty. In both these cases, the male and the female already have the genetic material from their parents.
To make it a bit simpler, let's call the parents generation 1, and the child generation 2
Generation 1 are adults therefore they have all their genetic material
Generation 2 is created as a result of reproduction by generation 1. This means generation 2 has all their genetic material from their parents.
As generation 2 develops, their cells undergo meiosis giving them (generation 2) the capacity to create
generation 3 once their bodies have matured to be able to do so
as they now have their own gametes that can be fertilised.
It's quite a difficult concept to understand, but when you said,
"how does one cell that is preparing for fertilisation already have the genetic material from both parents?" this cell 'preparing for fertilisation' is already inside a living organism created by reproduction, therefore they already have the genetic information from their parent.
Let me know if this still doesn't make sense!!