NOVA Online (see text links below)
18 Ways to Make a Baby  
How Cells Divide: Mitosis vs. Meiosis
Page 3 of 15 | Next | Previous



Chromosomes begin to condense, taking on the form that they are usually depicted in: four arms connected at a point. Each chromosome is, at this time, actually two identical copies. Each copy is called a chromatid.

A spindle begins to form from the centrioles. This spindle is made of fibers. The centrioles begin to separate.

Also, the membrane of the nucleus, or nuclear envelope, fragments and disperses.

Prophase I
The activities are the same as in mitosis, except that in this cell the chromosomes attach to the membrane of the nucleus and then pair up with their corresponding chromosome.

While paired up, enzymes cut sequences of DNA (genes) from the chromosomes. These sequences are exchanged between the chromosomes, which allows for an exchange of genes between the two.

Next | Previous
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15

Printer-Friendly Format   Feedback

The 18 Ways (And Then Some) | On Human Cloning | Fertility Throughout Life | How Cells Divide
Resources | Teacher's Guide | Transcript | Site Map | 18 Ways to Make a Baby Home

Search | Site Map | Previously Featured | Schedule | Feedback | Teachers | Shop
Join Us/E-Mail | About NOVA | Editor's Picks | Watch NOVAs online | To print
PBS Online | NOVA Online | WGBH

© | Updated October 2001

Support provided by

For new content
visit the redesigned
NOVA site

Shop Teachers Feedback Schedule Previously Featured Site Map Search NOVA Home 18 Ways to Make a Baby Home Site Map