Changes

**This suggests that cells have an intrinsic clock, goverened by the expression of a gene called "hairy".

**This suggests that cells have an intrinsic clock, goverened by the expression of a gene called "hairy".

**"Hairy" is expressed for 90 minutes at a time, and 12 cycles of 90 minutes each are required to make a somite.

**"Hairy" is expressed for 90 minutes at a time, and 12 cycles of 90 minutes each are required to make a somite.

**Somites are named beginning with which form first.

**Somites are named beginning with the most newly formed somite. Therefore, the greater the number of the somite, the older the and closer to the anterior of the embryo it is.

**As cycle one of somite one ends, cycle one of simte two begins; one somite forms every minute.

**As cycle one of somite one ends, cycle one of simte two begins; one somite forms every minute.

::'''Dermotome''' - develops into the dermis.

::'''Dermotome''' - develops into the dermis.

*Somites develop in an identical manner, although those at the posterior develop after those at the anterior.

*Somites develop in an identical manner, although those at the posterior develop after those at the anterior.