Cell Reproduction

Mitosis & Meiosis

http://biotech-adventure.okstate.edu/low/basics/mitosis/mitosis-diagram/diagram.gif

Cell Cycle

http://www.bmb.psu.edu/courses/biotc489/notes/cycle.jpg

Mitosis• One type of cell division

Cell process in which the nucleus divides to form two nuclei identical to

each other, and identical to the original nucleus, in a series of steps

(prophase, metaphase, anaphase, and telophase)

Mitosis allows for growth and replaces worn out or

damaged cells.

Interphase

• Period of growth & development• Hereditary information (DNA)

copied (replicated / duplicated)• Cells that do not divide (nerves)

are always in interphase

http://biotech-adventure.okstate.edu/low/basics/mitosis/phases/interphase/interphase.gif

Prophase

•DNA begins to shorten & thicken –Now called chromatids / chromosomes

•Centromeres form•Nuclear membrane breaks apart•Spindle fibers form

http://biotech-adventure.okstate.edu/low/basics/mitosis/phases/prophase/prophase.gif

Metaphase

•Chromatids / chromosomes line up•Centromere attaches to spindle fibers

http://biotech-adventure.okstate.edu/low/basics/mitosis/phases/metaphase/metaphase.gif

Anaphase

•Centromeres divide•Spindle fibers shorten•Chromatid pairs separate – move to ends of cell•Chromatids are now called

–Each ½ of the pair is now called a chromosome

http://biotech-adventure.okstate.edu/low/basics/mitosis/phases/anaphase/anaphase.gif

Telophase

•Spindle fibers disappear •Chromosomes uncoil•Nuclear membrane forms•Cell divides (cytokinesis)

http://biotech-adventure.okstate.edu/low/basics/mitosis/phases/telophase/telophase.gif

Interphase

                                                            

Prophase

                                                            

Metaphase

                                                            

Anaphase

                                                            

Telophase

                                                            

Interphase

                                                            http://biology.nebrwesleyan.edu/benham/mitosis/

Mitosis Animation

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

Results of Mitosis

• Division of nucleus– Nuclei are identical to each other

•Same number & type of chromosomes

Asexual Reproduction

A type of reproduction - fission, budding, and regeneration - in

which a new organism is produced from one parent and has DNA

identical to the parent organism.

Asexual Reproduction

•Offspring produced from one organism

•Hereditary information is identical

•Mitosis is one form of asexual reproduction

Sexual Reproduction

Meiosis

Sexual Reproduction

A type of reproduction in which two sex cells, usually an egg and a sperm, join to form a zygote, which will develop into a new

organism with a unique identity.

Sexual reproduction results in a great

variety, or diversity, of offspring.

Meiosis

• The nucleus divides twice– Meiosis I– Meiosis II

http://biotech-adventure.okstate.edu/low/basics/meiosis/diagram/

Interphase• DNA is duplicated

Prophase I

• DNA shorten & thicken– Forms chromatids / chromosomes

http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/prophase/leptotene/leptotene.gif

Metaphase I

•Copied chromatids / chromosomes line up in middle of cell

•Centromeres attach to spindle fibers

http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/metaphase-I/metaphase-I.gif

Anaphase I

•Chromatid pairs are pulled apart–They DO NOT separate

•Move to ends of cell

http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/anaphase-I/anaphase-i.gif

Telophase I

•Cell divides •No further replication of

hereditary material

http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/telophase-I/telophase-I.gif

There are now two cells. Both cells have

full sets of genetic material

(chromosomes)

Prophase II

•Similar to mitosis–Starts with TWO cells instead of one•Spindle fibers appear

http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/prophase-II/prophase-II.gif

Metaphase II

•Duplicated chromatid / chromosomes line up in middle of cell

•Spindle fibers attach to centromeres

http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/metaphase-II/metaphase-II.gif

Anaphase II

•Centromere divides –Chromatids separate & move to ends of cell•Chromatids are now individual chromosomes

http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/anaphase-II/anaphase-II.gif

Telophase II

•Spindle fibers disappear•Nuclear membranes form at

each end of cell•Cells divide

–Results in 4 cells •Each with ½ the original number of chromosomes

http://biotech-adventure.okstate.edu/low/basics/meiosis/phases/telophase-II/telophase-II.gif

Meiosis Animation

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

In summary:Meiosis

• Two cells form during meiosis I• In meiosis II, both of these cells form

two cells• The two divisions of the nucleus

result in four sex cells (gametes)• Each has one-half the number of

chromosomes in its nucleus that was in the original nucleus