Confusing terminology in Meiosis: Homologous chromosomes and Bivalent?

Hi so I'm just trying to make sense of meiosis, and I'm not sure I completely understand what these words mean. Do you think you could correct me on any which are wrong?

Chromosome: Two chromatids attached to each other, forming an X. You have one chromosome from your mum and one from your dad.

Homologous Pair: Each chromosome is copied. This means you have two of each chromosome so you have XX which are both exactly the same.

Bivalent: When a homologous pair XX attach to each other they form a bivalent and can then cross over.

So surely after interphase you have a homologous pair of each chromosome, so actually you have 4n? In my book it says after one division you have 2n, but it also says that after interphase you have 2n? Im stumped. Any help would be much appreciated

Hi so I'm just trying to make sense of meiosis, and I'm not sure I completely understand what these words mean. Do you think you could correct me on any which are wrong?

Chromosome: Two chromatids attached to each other, forming an X. You have one chromosome from your mum and one from your dad.

Homologous Pair: Each chromosome is copied. This means you have two of each chromosome so you have XX which are both exactly the same.

Bivalent: When a homologous pair XX attach to each other they form a bivalent and can then cross over.

So surely after interphase you have a homologous pair of each chromosome, so actually you have 4n? In my book it says after one division you have 2n, but it also says that after interphase you have 2n? Im stumped. Any help would be much appreciated

Chromosome: Two chromatids attached to each other, forming an X. You have one chromosome from your mum and one from your dad.

Homologous Pair: Each chromosome is copied. This means you have two of each chromosome so you have XX which are both exactly the same.

Bivalent: When a homologous pair XX attach to each other they form a bivalent and can then cross over.

Just noticed your definitions are a bit wrong, so to make them more precise:



A chromosome is simply a length of DNA. It's not always made up of two chromatids. It's only made up of two chromatids AFTER DNA replication.



Cells ALWAYS have pairs of homologous chromosomes (before and after DNA replication).
Homologous chromosomes are chromosomes that have the same structure and the same genes (not necessarily the same ALLELES) at the same loci. In one pair of homologous chromosomes, one chromosome is from the mum and one from the dad.
We've all got 23 pairs of homologous chromosomes, so 46 chromosomes in total.


'Bivalent' is just a name for homologous chromosomes that PAIR UP (NOT attach) during mitosis. They only 'attach' after they've already paired up, i.e. after they're already a bivalent. 'Attaching' is more correctly called 'crossing over'.