Question

In meiosis, recombination occurs_________.

a.during both prophases I and II and involves exchange of chromosome fragments between sister chromatids.
b.during both prophases I and II and involves exchange of chromosome fragments between all four chromatids.
c.during only prophase II and involves exchange of chromosome fragments between sister chromatids.
d.during only prophase I and involves exchange between chromatids of homologous chromosomes.

Answer 1

d.during only prophase I and involves exchange between chromatids of homologous chromosomes.

Step-by-step explanation:

Crossing over is the event that occurs during the pachytene stage of prophase I of meiosis I and results in the formation of new gene combinations, that is, recombination. During pachytene of prophase I, the synapsed homologous chromosomes exchange the genetic segments between them.

To facilitate recombination, synaptonemal complex assists in pairing the homologous chromosomes together during the zygotene stage of prophase I. Zygotene is followed by pachytene. A cut in two non-sister chromatids of a homologous pair, exchange of the broken segments followed by ligation results in recombination. Prophase II does not include crossing over.