Cell division

Mitosis

Daphnia

Females can produce offspring without a mate since they can produce eggs that require no fertilization.

Asexual reproduction Asexual reproduction occurs when food is

plentiful, while sexual reproduction is triggered during times of environmental stress.

Advantages and disadvantages?

Impressive numbers!

You are made of about 100 trillion cells and they all come from a single fertilized egg.

Red blood cells die and are replaced at a rate of one million every second

Why does a cell divide?

To replace old cells For the organism to grow Cells can’t keep on growing, they need to stay

small because diffusion is efficient on short distance only. Do p. 85 in Biology 11

Cell cycle

Interphase

Time interval between nuclear divisions. During this phase, a cell increases in

mass, roughly doubles the cytoplasmic components, and duplicates its chromosomes.

What does DNA looks like?

http://www.arikah.net/encyclopedie-francaise/images/thumb/5/5a/400px-Chromosome.gif

Duplication of DNA

How is replication done?

http://www.elmhurst.edu/~chm/vchembook/582dnarep.html

Action!

http://www.hschickor.de/dnarepli.html

Stop!

http://en.wikipedia.org/wiki/Image:DNA_replication.svg

Action again but with clarifications!

http://www.johnkyrk.com/DNAreplication.html

Mitose: Prophase

Pro-: prior to The chromosomes condense, becoming shorter

and thicker. The centrioles move to opposite poles of the

cell and spindle fibres start to form. Centrioles and spindle fibres = spindle

apparatus Spindle fibres attach to the centromeres of the

chromosomes. The nuclear membrane starts to dissolve.

http://img.sparknotes.com/figures/D/d756b5b73abe2974f3521a828791899f/prophase.gif

Examples of prophase

http://student.ccbcmd.edu/~gkaiser/biotutorials/dna/mitosis/pcprophaseB.html

Mitosis: Metaphase

Meta- : occurring later than Chromosomes composed of sister chromatids

move toward the equatorial plate.

http://www.microscopy-uk.org.uk/mag/artnov04macro/jronionroot.html

http://student.ccbcmd.edu/~gkaiser/biotutorials/dna/mitosis/acmetaphase.html

Mitosis: Anaphase

Ana- : upward, backward, again The centromeres divide and the sister

chromatids, now referred to as chromosomes, move to opposite poles of the cell.An image of a new lung cell stained with

fluorescent dyes undergoing mitosis, specifically during late anaphase. The material stained green are the mitotic spindles and the material stained light blue are the chromosomes. The cellular membrane is invisible during this photo.

http://commons.wikimedia.org/wiki/Image:300px-Anaphase-flourescent.jpg

Mitosis: Telophase

Telo- : end Chromosomes reach opposite poles of

cell and begin to lengthen. Spindle fibres dissolve And nuclear membrane forms around

each mass of chromatin.http://kcfac.kilgore.cc.tx.us/kcap1/images/whitefish%20mitosis%20telophase%201000x%20%20fireworks.jpg

Cytokinesis

Cytoplasm begins to divide In an animal cell, a furrow develops,

pinching off the cell into two parts. In plant cells, the separation is

accomplished by a cell plate that forms between the two chromatin masses. The cell plate will develop into a new cell wall

http://trc.ucdavis.edu/biosci10v/bis10v/week3/3webimages/figure-09-10a-photo.jpg

The cycle

http://www.rebeccastmartin.com/mnemonicdevices/phasescelldevelopment.htm

Did you know?

Telomeres are caps at the ends of chromosomes that prevent the chromosomes from sticking together.

It is thought that telomeres might play a role in the age of a cell.

Scientists have determined that telomeres are shaved down each time a cell divides. The length of the chromosomes of a 70-year-old human is much shorter than that of a child.

Scientists think it is the short length of chromosomes that is the signal to the cell that division can no longer occur.

What do you understand?

Do p. 90 questions # 1 – 11 but not #4 Do the Instructional Master 3.2E, Number the

phases and write the names underneath. Do the crossword puzzle Go online to look at mitosis in onion root tips

and count the different phases to figure out the length of the phases

Do a real onion root tips lab