Gene Regulation


Once upon a time...
there was a one-celled creature, called a zygote,
which was destined to grow up to be a Frog
[or an enchanted handsome Prince].

Meanwhile, back at the ranch,
there was an evil scientist with a vital dye which was red:
Frog
stage destiny
1-cell entire frog
2-cell anterior 1/2
posterior 1/2
4-cell dorsal, anterior 1/4
ventral, anterior 1/4
dorsal, posterior 1/4
ventral, posterior 1/4
8-cell right, dorsal, anterior 1/8
left, dorsal, anterior 1/8
right, ventral, anterior 1/8
left, ventral, anterior 1/8
right, dorsal, posterior 1/8
left, dorsal, posterior 1/8
right, ventral, posterior 1/8
left, ventral, posterior 1/8
and so forth...

  • 1-cell zygote had genetic information for all frog parts
  • by replication/mitosis all daughter cells also have genetic info for all parts
    . . -stems cells retain ability to become many different cells
  • some later cells exhibit only some traits, appropriate to a tissue
    . . -differentiation limits potential
    . . -or 'switches on' only some genes (or gene expressions).
    . . . Operon regulates gene expression (by transcription)
    . . . normally "off" operon is "activator"
    . . . normally "on" operon is "repressor"



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    © 2004 Prof. LaFrance, Ancilla College