Download Asexual Reproduction - Mitosis How and why do cells reproduce

Asexual Reproduction - Mitosis
How and why do cells reproduce themselves? S7L2a
1. Asexual reproduction: production of offspring by a single parent, without sperm or egg; DNA comes from a single
parent; offspring normally identical because its chromosomes duplicate themselves and divide so that each offspring
(daughter) cell has a full set of chromosomes that are identical to the original (mother) cell.
2. Eukaryotic cells reproduce asexually by MITOSIS and CYTOKENESIS; Mitosis refers to the equal division of the
nucleus, and cytokenesis refers to the division of the rest of the cell. Phases in a cell's life cycle are as follows:
A. Interphase: normal growth, development, functions and preparation for division and replication of chromosomes
(DNA); chromosomes copy themselves and other organelles are produced just before mitosis begins.
Interphase
http://upload.wikimedia.org/wikipedia/commons/b/b5/Interphase.png
B. Mitosis: Equal division of nuclear
in four phases
contents to form two identical nuclei; occurs
1. Prophase: chromatin becomes visible
Centrioles double, separate and create
as chromatids, nuclear envelope dissolves;
spindle from one pole to the other
Prophase
http://upload.wikimedia.org/wikipedia/commons/d/db/Prophase.jpg
2. Metaphase: chromatids line up at middle of cell (equator) and attach centromeres to spindle fibers created when
Centrioles separated
Metaphase
http://upload.wikimedia.org/wikipedia/commons/1/19/Metaphase.jpg
3. Anaphase: chromatids separate at centromeres and are pulled by spindle fibers to opposite poles of cell
Anaphase
4. Telophase: chromatids uncoil to
reforms, cell begins to separate to
Telophase
appear as chromatin, nuclear envelope
become two
http://upload.wikimedia.org/wikipedia/en/c/c5/Telophase.jpg
C. Cytokenesis: separating into two cells is completed:
1. animal cells first develop a "furrow",
completely surrounds both new cells
then pinch in two so that cell membrane
2. plants cells grow a new cell plate
become a cell wall.
Anaphase Interphase
Prophase
between two new nuclei which grows to
Metaphase & Telophase
Cytokenesis
http://upload.wikimedia.org/wikipedia/commons/thumb/e/e0/Major_events_in_mitosis.svg/350pxMajor_events_in_mitosis.svg.png
3. Factors that affect cell division:
A. Surface to volume ratio: has to divide when nutrients and wastes can no longer pass quickly in and out of entire
cytoplasm
B. Density Dependent Inhibition: cells will anchor and grow to fill an area; touch on all sides inhibits further division;
removal of cells makes room and cells will divide to fill area again
C. Density Dependent Inhibition: proteins that can stimulate cell division even in a limited space; cells will just remain
small; control factors regulate every step of cell division
D. Cancers: cells divide without regard to control factors
1. Benign tumors: cells divide without regard to control factors
2. Malignant tumors: uncontrolled growth of cells that are abnormal, may break away and move to other locations (called
metastasis); difficult to remove completely; can grow and divide indefinitely; classified by where cancer cells first start to
grow:
a. Carcinomas: originate on skin or intestine lining
b. Sarcomas: originate in bone or muscle
c. Leukemia: originates in bone marrow or spleen
d. Lymphomas: originate in lymph nodes
4. Functions of Mitosis: growth, replacement of dead or damaged cells, and asexual reproduction; assures each new
daughter cell will have the exact same number and kinds of chromosomes as the mother cell; occurs in somatic (body
tissue) cells
5. Chromosomes: there are two types:
A. Autosomes — those that are found in both male and females which determine most traits; humans have 22 pairs of
autosomes.
B. Sex Chromosomes Autosomes — those that are found in both male and females which determine most traits that make
each unique; humans have one pair of sex chromosomes.