Cell Division - Mitosis

Chapter 9

I. Review of Cell NucleiA. nuclear membrane, nuclear pores, nucleoplasm

B. contains chromosomes

1. long piece of DNA wound tightly around supporting proteins

2. karyotyping – a way of organizing and viewing chrom.

3. chromatin and chromosome number

C. chromosomes occur in pairs1. one came from each parent

2. each member of a pair is basically identicala. size, shape, genetic material

b. homologous chromosomes

Homologous chromosomes of a human male

II. Diploid vs. Haploid CellsA. most of an organism’s cells are diploid (2n)

1. normal # of chromosomes

2. produced through mitosis• somatic cells

B. an organism’s sex cells are haploid (n)1. gametes

• egg and sperm

2. ½ normal # of chromosomes

3. produced through meiosis• germ cells

III. The Cell CycleA. a way of looking at entire lifespan of a cell

1. begins when cell is produced, ends when cell divides

2. growth, replication, and division (reproduction)

3. mitosis

a. 1:2 cell division

b. parent and daughter cells

c. daughter cells identical to each other and parent cell

B. divided into two basic phases1. interphase

a. normal state of a cell • growth, metabolism, functions

b. time of interphase varies

c. G1 phase

i. growth, high metabolism, protein synthesis

ii. each chromosome is a single DNA molecule

d. S phase

i. all DNA is replicated

ii. sister chromatids and centromeres

e. G2 phase

• preparatory stage for mitosis

2. mitosis (M phase)

Fig. 9.3 Duplicated chromosomes

Fig. 9.1 The cell cycle

IV. Stages of Mitosis

A. prophase1. early prophase

a. nucleolus and nuclear envelope disappear

b. centrioles migrate to opposite poles

c. chromatin thickens into full chromosomes

2. late prophase (prometaphase)

a. spindle fibers form off centrioles and become visible• asters

b. spindle fibers attach to centromeres• kinetochore

Fig. 9.4a Prophase

B. metaphase• chromosomes line up, single file, down center of cell

o equatorial plane

C. anaphase1. centromeres of each chromosome divide in half

2. sister chromatids detach

3. spindle fibers pull sister chromatids toward opposite poles

D. telophase1. spindle fibers disappear

2. centrioles return to normal position

3. nucleolus and nuclear envelope reform

4. chromosomes unravel back into chromatin

Fig. 9.4b Metaphase, anaphase, and telophase

Fig. 9.4 Mitosis, complete

E. cytokinesis1. division of cytoplasm

2. plasma membrane furrows and cleaves (cleavage)

3. two identical daughter cells are produced

4. in plants, a new cell wall begins as a cell plate

5. does not have to occur in all cells of all organisms• if it doesn’t multinucleated tissue

V. Advantages and Functions of MitosisA. primary means of asexual reproduction

B. all growth takes place through mitosis• cancer: uncontrolled cell division/growth

C. repair or replacement of old, damaged, or malfunctioning cells

D. allowing cell specialization to occur

VI. Mitosis vs. ApoptosisA. apoptosis

1. programmed cell death

a. natural lifespan of cell is over cell dies without dividing

b. determined genetically

2. series of cellular reactions that lead to death of a cell

3. cell fragments phagocytized by white blood cells

B. # of body cells increased by mitosis, decreased by apoptosis

Fig. 9.2 Apoptosis