crossing over (1 Viewer)

[demosthenes]

No, not the show with John Edwards....
it is urgent.
Can someone please explain (in simpleton terms) thr process of crossing overduring meiosis in homologous chromosomes?
cheers!

PS VERY STRESSSED have 1/2 yearly bio tomorrow

 

[bluesky100]

I hope this info helps:

-In the 1st meiotic division the homologous chromosomes attach to one another by a protein complex
-This brings chromatids from the 2 homologues into contact with each other and sometimes they cross
-Cross-overs help to hold homologous chromosomes together
-At the cross-over the 2 chromatids can exchange tips (recombination)
*The exchange is catalyzed by enzymes
*Promotes genetic diversity
*Homologous chromosomes can have more than 1 cross-over

-The cross-over process is unbelievably precise
*Average human chromosome has about 100 million DNA base pairs
*In cross-overs neither chromosome can gain or lose a single base pair

Good explanation and animated gif here - http://www.people.virginia.edu/~rjh9u/meiosisx.html