Is there such thing as crossing over of sister chromatids?

Question

shrutipande9 · Answer

crossing over between sister chromatids can occur...but there would be no genetic variation as the genetic make up of sister chromatids is just the same...so no phenotypic change as well....

xanven · Answer

In both meiosis and mitosis?

shrutipande9 · Answer

see in meiosis synaptonemal complex is formed between 2 homologous chromsomes which has all the enzymes required for recombination....so the recombination occurs....but in case of mitosis this does not happen...so crossing over in mitosis is vry rare.

xanven · Answer

Thanks :) What about random assortment of homologous chromosome? actually i dont even understand the term of random assortment of homologous chromosome... and does it occur in both meiosis and mitosis? from my understanding,i think it only occur in 
meiosis...

shrutipande9 · Answer

yes meiosis...because in mitosis u retain the chromosomal no so there is no assortment as such.....

shrutipande9 · Answer

assortment would be like....see if we name each homologous chromosome as A nad B. So like v will have chromosome no 22a and 22 b in that manner. so during meiosis u can hv either A in 1 cell or B. and then u can hv 1000s of combinations of 23 chromosomes....this is assortment. and this is completely random

xanven · Answer

Wow thanks because i was facing this question and i had no model answer for it.
Which process(es) take(s) place in meiosis but not in mitosis?

A) pairing of homologous chromosomes
B) fusion of kinetochores of sister chromatids
C) crossing over of the sister chromatids
D) crossing over between homologous chromosomes
E) random assortment of homologous chromosomes

This question has multiple correct answers. Am i correct to say that all A B C D E are the answers for this question?

shrutipande9 · Answer

See crossing over occurs to create genetic variation...but this doesn't occur during sister chromatid cross over. This crossing over is rare almost equal to no cross over. This is wat I think...so apart frm C everything

xanven · Answer

Okay thank you very much :)!! this helps a lot