Newbie Question on Crossing over

[Knoxy]

Hi!!

 

I am a high school student.

 

Just have a confusion that.

 

Is crossing over occurs in all chromosomes of a cell?

[Genecks]

Crossing over doesn't occur in all species and in all cells.

For instance, male fruit flies don't have crossing over.

So, don't expect the chromosomes in their cells to undergo crossing over.

 

In terms of humans, there are cases during which crossing over occurs between chromosomes. Crossing over doesn't happen all the time for all chromosomes. It does happen a lot, though.

 

Also, you need to keep in mind what kind of cells you are talking about, as the process occurs during meiosis.

 

Crossing over occurs a lot in autosomal chromosomes, which leads to genetic variation (various physical and genetic attributes: phenotypes/genotypes) within offspring.

 

http://www.hcs.ohio-state.edu/HCS300/genetic.htm

 

Take a look at prophase I.

 

Although I don't know the statistics of human meiosis and crossing over, I would 'guess' that there is a lot of crossing over occurring, but that doesn't mean it is always happening in all of the chromosomes.

Edited October 25, 2009 by Genecks

[Knoxy]

.

For instance, male fruit flies don't have crossing over.

So, don't expect the chromosomes in their cells to undergo crossing over.

 

So it means all genes present in a particular chromosome got inherited together and there is no chance of recombination in male fruit flies.

 

Am I right?