Prophase 1 of Meiosis

enough with the hormone rush. lets talk about the real thing. the 4 stages of Prophase 1(LZPDD).

* Leptotene

* Zygotene

* Pachytene

* Diplotene

* Diakinesis

*mind the arrows

Leptotene(thin threads)
-individual chromosomes begin to condense into long strands within the nucleus. sister chromatids are indistinguishable as they are so tightly bound.

Zygotene(paired threads)
-chromosomes approximately line up with each other into homologous chromosomes.

Pachytene(thick threads)
-chromosomal crossover! nonsister chromatids of homologous chromosomes randomly exchange segments of genetic information over region homology. in sex chromosomes (X and Y), exchange of information is only over small region of homology. results in a recombination of information.
-exchange site: chiasmata/recombination nodules

Diplotene(two threads)
-synaptonemal complex degrades and homologous chromosomes separate from one another, a little. chromosomes themselves uncoil a bit, allowing some DNA transcription of DNA. but the homologous chromosomes of each bivalent remain tightly bound at chiasmata/recombination nodules

Diakinesis(moving through)
-four parts of tetrads are visible. sites of crossing over entangle together, effectively overlapping, making chiasmata clearly visible.
-closely resembles prometaphase of mitosis; nucleoli disappear, nuclear membrane disintegrates into vesicles, meiotic spindle/spindle fibre begins to form.

*this one feels better, 'cus it's my field =)