[PDF] Cell Reproduction

43563_7MitosisMeiosis.pdf

Cell Reproduction

Mitosis & Meiosis

CELL DIVISION

™allows organisms to grow, repair damaged

structures and reproduce

™single-cell organisms: reproduce/make

more of their kind when one cell divides itself

™multi-cell organisms: can reproduce when

VSHŃLMO ŃHOOV IURP PRR ³SMUHQPV´ ŃRPNLQH PR make a new cell

¾this new cell keeps dividing and a new

organism/living thing is formedver

CELL CYCLE

™when a cell grows,

prepares to be divided, and then divides into 2 QHR ³GMXJOPHU´ ŃHOOV

¾HMŃO ³GMXJOPHU´ POHQ

begins the cell cycle again

™3 stages:

interphase, mitosis, cytokinesis

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

‡DNA replication (copied)

‡Cells that do not divide (nerves)

are always in interphase

‡Cells spend most of their time

here. 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/

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

™process of cell division where the

number of chromosomes is reduced [made less] by half

¾chromosome pairs separate into 2

different cells, then divide again (total of four cells)

¾chromosomes duplicate (make a

copy) before the first cell division 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

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