1. Do Now & Homework Check
Miss Pollack

2. A key part of cell division is to create copies of the genetic material. There are different
names for the genetic material depending on the form it takes. It’s important to know the
differences between these terms. FILL IN THE BLANKS in your notebook for #1-4
1.___________________
• When DNA is not
dividing it is sitting in
the nucleus, and so the
DNA is not tightly
coiled yet
• Loosely packed
• Not condensed
*SPAGHETTI*
3._______________
• DNA condensed into a
transportable form after
it has replicated; humans
have 46 individual and 23
pairs of these
2._______________
• The identical
halves of a
chromosome;
each half is
attached by the
centromere
_________________
chromosomes
• A pair of 2
chromosomes that are
the same size, shape &
contain the same genes,
with each parent
contributing one of the
chromosomes in the pair

3. Cell Reproduction/Cell Division
• Cells in your body are constantly reproducing
– Approximately 25 million cells per second
• Why do our cells do this?
– Part of growth and maturing as a human/organism
– Cells in your body may be dying or damaged and we need to
replace them
• As we know from the cell theory, all cells come from
preexisting cells
–Get 2 new cells from 1 original cell

5. Cell Division: Prokaryotes
• Prokaryotes have a single,
circular chromosome
• Do binary fission
– 3 steps
– End result: Get 2 new cells
from 1 original cell

6. • Binary fission has 3 steps:
– 1. DNA is replicated so that there are 2 identical
chromosomes.
– 2. The 2 chromosomes separate and move to opposite ends of
the cell.
– 3. Cytokinesis: a new membrane grows at the center of the cell
and the cytoplasm splits apart, forming 2 new daughter cells
• End result: 2 new cells that are genetically identical to each
other and to the 1st original cell

8. Cell Division: Eukaryotes
• Eukaryotic cells = humans, mammals, fish–
do NOT go through binary fission
• Go through a cell cycle= period from the
beginning of one division to the beginning of
the next; life cycle of a cell
– Cell cycle has 2 periods:
• 1. Interphase = a cell spends MOST OF its life here
• 2. Mitosis = shorter period for the cell to be in

9. Period 1- Interphase
• Interphase = the time between cell divisions; also is the
longer period compared to mitosis
• cell has not yet started to divide but is doing its regular
activities like making the proteins/ enzymes it will need
later on
– 3 subphases:
• 1. G1: cell grows
• 2. S phase: (synthesis) each chromosome is copied (DNA
copied)
• 3. G2: prepares for cell division, growing again
– G0: cells do not copy their DNA and do not prepare
for cell division  in a resting stage, just hanging
out after they go through G1
• Ex: Nerve cells, or other mature cells that do not need
more development

10. G0
CELL CYCLE ALIVE!
Cell Cycle

11. Think- Pair- Share
• Give evidence…that the eukaryotic cell is more
complex than the prokaryotic cell
– Think and explain your reasoning in your CW ntbk
– Pair up with your neighbor
– Share as a class

12. MONDAY- Do NOW
• 1. What are autosomes?
– How many pairs of autosomes do humans have?
• 2. What are sex chromosomes?
– How many pairs of sex chromosomes do humans
have?

13. So what is the purpose of mitosis?
• Produce daughter cells that are identical copies
of the parent cell for all the cells in the body,
except sex cells/gametes
• Maintain the correct number of chromosomes
from generation to generation

14. Period 2: Mitosis
• Now that the chromosomes have been copied
in the S phase of interphase…
• Can now go through mitosis:
– Division of the nucleus to give the cell’s copied
DNA to new cells
• The cell is dividing in 4 steps:
– PMAT
– Prophase, metaphase, anaphase, telophase
– cytokinesis

15. Mitosis: Prophase
• 1st
• Chromosomes thicken and
coil, condense
– Allows them to be visible for
first time
• Nuclear envelope
disappears
• Centrioles move to
opposite ends of the cell
• Spindle fibers/strings
attach to chromosomes

16. Metaphase
• 2nd
• Spindle fibers are
attached to
centromere of
chromosome
• Chromosomes line
up at the equatorial
plane or metaphase
plate
– Middle

17. Anaphase
• 3rd
• Sister chromatids of each chromosome
separate at the centromere
– Go to opposite poles, pulled apart
– Each half of a pair of sister chromatids now moves
to opposite ends

18. Telophase
• 4th (reverse of prophase)
• Spindle fibers disappear
• Chromosomes uncoil to become chromatin
• Nuclear membrane forms around each set of
chromosomes

20. Cytokinesis
• Split the cytoplasm, done in the middle too
– Get the 2 DISTINCT DAUGHTER CELLS
• Animals form a furrow to pinch off
• Plants form a cell plate

21. In mitosis…
• … what happens if this does not go as
planned? What happens if we do not get
identical copies of the parent cell? What
happens if you do not get the correct number
of chromosomes?