Transcript chromosome sister copy centromere

The Cell cycle:
• Just as you have a distinct life cycle, so do
cells.
• You spend most of your life growing and
maturing, and only a small portion of your
life reproducing.
• The same is true for cells.
INTERPHASE
• Phase between cell
division
• Cell grows
• DNA is uncoiled and
invisible (chromatin)
• DNA copied
The process of cell division
is called:
• Mitosis
• “I hit my toe sis!”
• The mitosis consists of many different stages
The most important part of cell
division:
• Making sure the right number
chromosomes end up in both cells
• You have 46 chromosomes in every cell
• Thus each cell must make a copy of each
chromosome before it divides
Mitosis Stage 1:
PROPHASE
• nuclear membrane breaks
down
• Chromatin wind to become
visible chromatids
• chromatids (pairs of
chromosomes) stay
attached by a centromere.
• Centrioles (poles) appear
and move to opposite sides
of cell
• Spindle fibers form
between poles
Chromatids
• Two identical
chromosomes
joined at a
centromere
CHROMOSOME
CENTROMERE
SISTER COPY
Stage 2:
Metaphase
• Chromotids attach to
spindle fibers
• Chromotids line up on
midline (equator) of
cell (meet in middle)
Stage 3:
Anaphase
• Chromatids separate
and move to opposite
ends of the cell
• Centromere splits in
half
Stage 4:
Telophase
• Spindle disappears
• Chromosomes
unwind and become
less visible
• Nuclear membranes
form around the new
sets of chromosomes
• Cell begins to pinch
into two
• Mitosis ends
Cytokinesis
• The division of the
rest of the cell
organelles roughly in
half
• Two daughter cells
are completely
formed
How to remember the order:
•
•
•
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•
•
I
Pee on the
M
A
T
C (see)
Assignment:
• P 25-26 in the workbook Q#1-12