Prophase I
The first stage of Prophase I is the leptotene stage, also known as leptonema, from Greek words meaning "thin threads."[
During this stage, individual chromosomes begin to condense into long strands within the nucleus. However the two sister chromatids are still so tightly bound that they are indistinguishable from one another.
IMPORTANT FOR YOU-
The zygotene stage, also known as zygonema, from Greek words meaning "paired threads," occurs as the chromosomes approximately line up with each other into homologous chromosomes.
The combined homologous chromosomes are said to be bivalent.
They may also be referred to as a tetrad, a reference to the four sister chromatids. The two chromatids become "zipped" together, forming the synaptonemal complex, in a process known as synapsis.
In meiosis II there are no homologous chromosomes to pair off.
That is why synapsis is impossible . Only sister chromatids are separeted in this phase.
Click on the links to see photo-
http://www.biologycorner.com/bio4/notes/meiosis.php
http://faculty.ircc.edu/faculty/tfischer/images/meiosis%202.jpg
http://www.biologycorner.com/resources/meiosis2.gif
Enlarge the picture below by clicking again on the inset arrows-
http://www.mun.ca/biology/desmid/brian/BIOL2060/BIOL2060-20/2009.jpg
2007-03-26 23:57:24
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answer #1
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answered by Anonymous
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