Vocabulary
1. Chromosome
2. Histone
3. Chromatid
4. Centromere
5. Chromatin
6. Sex chromosome
7. Autosome
8. Homologous chromosome
9. Karyotype
10. Diploid
11. Haploid
12. Binary fission
13. Mitosis
14. Asexual reproduction
15. Meiosis
16. Gamete
17. Interphase
18. Cytokinesis
19. Prophase
20. Spindle fiber
21. Metaphase
22. Anaphase
23. Telophase
24. Cell plate
25. Synapsis
26. Tetrad
27. Crossing over
28. genetic recombination
29. Independent assortment
30. Sexual reproduction

Cells Division Introductory Video

• During cell division the cell’s DNA is coiled compactly into a
CHROMOSOME
• Each chromosome is a single DNA molecule
• The DNA wraps tightly around a protein called
HISTONE (helps maintain the chromosome’s shape
)
The
Chromosome

Anatomy of a Chromosome
• Each half of a chromosome is called a CHROMATID
• Chromatids form as the DNA copies itself before cell division
• The 2 Chromatids are attached at a point called a CENTROMERE
• CHROMATIN=less tightly areas of
DNA between cell divisions

Chromosome Numbers
• Every species has a certain number of chromosomes in each cell.
• Animal chromosomes are either:
• Sex Chromosomes—will determine the gender of an organism (X and Y)
• Autosomes—all of the other chromosomes
• Cells with 2 sets of Chromosomes are
DIPLOID
• Cells with one set of chromosomes are
HAPLOID (sex cells…half the number of chromosomes)

Chromosomes Clip
• How many chromosomes does a potato have?
• How many chromosomes do Ferns have?
• After the video…in your own words why do different organisms have different numbers of chromosomes??

Cell Division (aka Cell
Reproduction) in Prokaryotes
• Most prokaryotes reproduce by BINARY
FISSION
• 2 identical cells are produced from one cell
• Draw this

Cell Division Eukaryotes
• Two types of Cell Division
(Reproduction) in
Eukaryotes!
• Mitosis=new cells with identical genetic material
• Meiosis=reduces the number of chromosomes by half for the purpose of eventual reproduction

The Cell Cycle
• The CELL CYCLE is the repeating events of the life of a cell.
• Interphase is the period between cell divisions
• Draw the diagram 

Quick Lab: Prefixes and Suffixes
• Use a dictionary or online source to look up the definitions for the following terms:
• Pro-
• Meta-
• Ana-
• Telo-
• Cyto-
• Oo-
• Inter—
• --kinesis
• --genesis
• Write the prefix or suffix on notecards, write the definitions on another card
• Play Memory with a partner

How do little elephants grow up to be BIG elephants?

Mitosis Cycle
• Interphase
• Prophase
• Metaphase
• Anaphase
• Telophase & Cytokinesis

occurs before mitosis begins
• Chromosomes are copied (# doubles)
• Chromosomes appear as threadlike coils (chromatin) at the start, but each chromosome and its copy(sister chromosome) change to sister chromatids at end of this phase
CELL
Nucleus
MEMBRANE
Cytoplasm

Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

1 st step in Mitosis
• Mitosis begins (cell begins to divide)
• Centrioles appear and begin to move to opposite end of the cell.
• Spindle fibers form between the centrioles.
• DNA is coiled into chromosomes
Centrioles
Sister chromatids
Spindle fibers

Animal Cell Plant Cell
Spindle fibers
Centrioles
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

2 nd step in Mitosis
• Chromatids (or pairs of chromosomes) attach to the spindle fibers.
• Chromosomes/chromatids are easily identified in this stage
Centrioles
Spindle fibers

Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

3 rd step in Mitosis
• Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell.
Centrioles
Spindle fibers

Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

4th s tep in Mitosis
• Two new nuclei form.
• Chromosomes uncoil and become chromatin, the new nucleus forms around it
• Mitosis ends.
Nuclei Nuclei
Chromatin

Animal Cell Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

occurs after mitosis
• Cell membrane moves inward to create two daughter cells – each with its own
nucleus with identical chromosomes .
• The cell splits into 2

Animal Mitosis -- Review
Interphase Prophase
Metaphase
Telophase
Anaphase
Cytokinesis

Plant Mitosis -- Review
Interphase Prophase
Metaphase
Telophase
Anaphase
Cytokinesis

I nterphase
P rophase
M etaphase
A naphase
T elophase
C ytokinesis
I P ___ M ___ A ___ T ___ C ______

Label it!

Brainpop Mitosis

Mitosis in an
Onion

Stages of Mitosis Animation

It’s your turn! Identify the stages of mitosis…

Mitosis Dance Video

Mitosis Flash Cards!
• Draw each stage
• Describe each stage on the back
• Replicate the stage with pipe cleaners!
• Play games:
• sort in the correct sequence, time yourself!
• Sort in the correct sequence, beat someone else!
• Play memory—match picture to description

Control of Cell Division!
• What triggers a cell to leave interphase and begin dividing? What tells the cell to stop?
• Proteins regulate this process through a series of
‘check points’
• Certain signals at checkpoints tell the cell to initiate the next step in the cell cycle or to halt the cycle

3 Main Checkpoints
G1 Checkpointcell growthproteins control whether the cell will divide or not
If cell is healthy and the right size, DNA synthesis will begin (S phase)
G2 Checkpoint-DNA
Synthesis– enzymes check results of DNA replication…if ok Mitosis will begin
Mitosis Checkpoint: If a cell passes this checkpoint, proteins signal the cell to exit mitosis and it enters
G1 again

When Control is LOST: Cancer
• The proteins that regulate cell growth and division are coded for by genes, proto-oncogenes.
• If a mutation occurs in one of those genes, the proteins may not function properly and become oncogenes.
• If the proteins don’t function properly Cancer can result: an uncontrolled growth in cells

When Control is LOST: Cancer
• A TUMOR is an uncontrolled growth of unnecessary cells.
• In a BENIGN tumor the cells stay in the mass and the are generally harmless
• In a MALIGNANT tumor, the uncontrolled dividing cells may invade and destroy healthy tissues= CANCER

Cancer Research and Clinical Trials

Meiosis – key differences from mitosis
• Meiosis reduces the number of chromosomes by
half, producing GAMETES (sperm and egg cells in humans).
• Daughter cells differ from parent, and each other.
• Meiosis involves two divisions, Mitosis only one.
Meiosis KM 50

Meiosis I (four phases)
• Cell division that reduces the chromosome number by one-half.
• four phases : a. prophase I b. metaphase I c. anaphase I d. telophase I

Interphase I
• Similar to mitosis interphase.
• Chromosomes replicate (S phase).
• Each duplicated chromosome consist of two identical sister chromatids attached at their centromeres .
• Centriole pairs also replicate.

Interphase I
• Nucleus and nucleolus visible
.
chromatin nuclear membrane cell membrane nucleolus

Prophase I
• Longest and most complex phase (90%).
• Chromosomes condense.
• Synapsis occurs: homologous chromosomes come together to form a tetrad .
Unique to
MEIOSIS
• Tetrad is two chromosomes or four chromatids (sister and nonsister chromatids).

Homologous Chromosomes
• Pair of chromosomes ( maternal and paternal ) that are similar in shape and size.
• Homologous pairs (tetrads) carry genes controlling the same inherited traits.
• Each locus (position of a gene) is in the same position on homologues.
• Humans have 23 pairs of homologous chromosomes.
a.
22 pairs of autosomes b.
01 pair of sex chromosomes

Homologous Chromosomes eye color locus eye color locus hair color locus
Paternal Maternal hair color locus

Prophase I
-
Synapsis
Homologous chromosomes sister chromatids
Tetrad sister chromatids

Prophase I spindle fiber aster fibers centrioles

Crossing Over
• Crossing over (variation) may occur between nonsister chromatids
• Crossing over : segments of nonsister chromatids break and reattach to the other chromatid .
• Crossing Over creates genetic recombination (variety)

Crossing Over - variation nonsister chromatids
Tetrad chiasmata: site of crossing over variation

Crossing-Over
Crossing-over multiplies the already huge number of different gamete types produced by independent assortment.

Metaphase I
• Shortest phase
• Tetrads align on the metaphase plate .

Metaphase I
OR metaphase plate metaphase plate

Anaphase I
• Homologous chromosomes separate and move towards the poles.
• Sister chromatids remain attached at their centromeres .
• INDEPENDENT ASSORTMENT OCCURS:
1. The random separation of the homologous chromosomes ---this results in GENETIC VARIATION

Anaphase I

Telophase I
• Each pole now has haploid set of chromosomes .
• Cytokinesis occurs and two haploid daughter cells are formed.

Telophase I

Meiosis II
• No interphase II
(or very short - no more DNA replication )
• Remember: Meiosis II is similar to mitosis

Prophase II
• same as prophase in mitosis

Metaphase II
• same as metaphase in mitosis metaphase plate metaphase plate

Anaphase II
• same as anaphase in mitosis
• sister chromatids separate

Telophase II
• Same as telophase in mitosis .
• Nuclei form.
• Cytokinesis occurs.
Remember:
• four haploid daughter cells
• gametes = sperm or egg produced.

Telophase II

Meiosis – mouse
Parent cell
1 st division
2 nd division
4 gametes

Meiosis I
Draw
This!

Meiosis
II
Draw
This!

Meiosis

Sex Chromosomes
The Sex Chromosomes code for the sex of the offspring.
** If the offspring has two “X” chromosomes it will be a female .
** If the offspring has one “X” chromosome and one “Y” chromosome it will be a male .
In Humans the
“Sex
Chromosomes” are the 23 rd set
XX chromosome - female XY chromosome - male

Boy or Girl? The Y Chromosome “Decides”
X chromosome
Y chromosome

Cells Dividing Clip

Crash Course Meiosis

Is he my brother or not?

Venn Diagram Mitosis vs. Meiosis

Snowball Fight!