Cell Growth and Division

Vocabulary

1. Cell division2. Chromatid3. Centromere4. Interphase5. Cell cycle6. Mitosis7. Prophase8. Metaphase9. Anaphase

10. Telophase11. Cytokinesis12. Homologous13. Diploid14. Haploid15. Meiosis16. Tetrad17. Crossing-over

Cell Division

•Before a cell becomes too large it divides and forms to DAUGHTER Cells. This process is called CELL DIVISION (or reproduction).

•Cell Division Video Clip

The Chromosome

•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)

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??

The Cell Cycle

•The CELL CYCLE is the repeating events of the life of a cell.

• Interphase is the period between cell divisions

•Lab: Prefixes and Suffixes

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

Prefix/Suffix quiz!

Interphase 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 MEMBRANENucleus

Cytoplasm

Interphase

Animal Cell Plant Cell

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

Prophase 1st step in Mitosis

• Mitosis begins (cell begins to divide)• Longest phase

CentriolesSister chromatids

Spindle fibers

Prophase

Animal Cell Plant Cell

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

Spindle fibers

Centrioles

Metaphase 2nd step in Mitosis

•Chromatids (or pairs of chromosomes) attach to the spindle fibers.

Centrioles

Spindle fibers

Metaphase

Animal Cell Plant Cell

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

Anaphase 3rd step in Mitosis

•Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell.

Centrioles

Spindle fibers

Anaphase

Animal Cell Plant Cell

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

Telophase 4th step in Mitosis

• Two new nuclei form. • Chromosomes appear as chromatin• Mitosis ends.

NucleiNuclei

Chromatin

Telophase

Animal Cell Plant Cell

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

Cytokinesisoccurs after mitosis

•Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes.

REMEMBER!

InterphaseProphaseMetaphaseAnaphaseTelophaseCytokinesis

IPMATC

I P___ M___ A___ T___ C______

Label it!

Brainpop Mitosis

Stages of Mitosis Animation

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

Mitosis Dance Video

Mitosis Review

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 Checkpoint-cell growth-

proteins 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

Defining Cancer•Read and annotate text

•Min. of 5 highlights•Chunk into min. of 3 sections•Min. of 3 summaries in margins

•Use the internet to find a list of cancers•Choose 1 (must be cleared by teacher)•You will create a brochure that could help someone who has just been diagnosed with a particular kind of cancer to understand his or her disease and its treatment options.

Required: • Cancer type

• Some graphic or drawing

• Your name and period

• Symptoms associated with this type of cancer

• Risk factors – what makes people more likely to get it? Is it genetic or caused by a carcinogen, or both?

• How common is it?

• Is any particular group more likely to get it than another?

• Treatment Options

• Interesting facts

MEIOSIS

Meiosis KM 38

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 I (four phases)

• Cell division that reduces the chromosome number by one-half, to create 4 haploid cells (instead of 2 like Mitosis).

four phases:a. prophase Ib. metaphase Ic. anaphase Id. telophase I

Prophase I• Longest and most complex phase (90%).

• Chromosomes condense.

•Synapsis occurs: homologous chromosomes come together to form a tetrad.

•Tetrad is two chromosomes or four chromatids (sister and nonsister chromatids).

Unique to MEIOSIS

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 autosomesb. 01 pair of sex chromosomes

Homologous Chromosomes

Paternal Maternal

eye color locus

eye color locus

hair color locus

hair color locus

Prophase I - Synapsis

Homologous chromosomes

sister chromatids sister chromatidsTetrad

Prophase I

centriolesspindle fiber

asterfibers

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

chiasmata: site of crossing over

variation

Tetrad

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

metaphase plate

OR

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 platemetaphase 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

produced.• gametes = sperm or egg

Telophase II

Meiosis – mouseParent cell

4 gametes

1st division

2nd division

Meiosis I

Draw This!

Meiosis II

DrawThis!

Meiosis

Sex ChromosomesThe 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.

XX chromosome - female XY chromosome - male

In Humans the “Sex

Chromosomes” are the 23rd set

Boy or Girl? The Y Chromosome “Decides”

X chromosomeY chromosome

Cells Dividing Clip

Meiosis Pipe Cleaner Lab

Snowball Fight!