Ch. 10 Cell division notes

1. CHAPTER 10 CELLULAR REPRODUCTION
The Cell Cycle and Mitosis
PHASES OF THE CELL CYCLE
I. INTERPHASE or RESTING PHASE - portion of the cell cycle between divisions
- during this stage, cells carry on their usual functions like: cellular respiration;
growth and development
- it is the LONGEST STAGE
PHASES OF INTERPHASE
1. Gap 1 or G1 PHASE - the number of organelles and the amount of cytoplasm
increases. Cell takes in a lot of water and nutrients from its environment.
2. Synthesis or S PHASE – chromosomes of the cell replicates.
REPLICATION - process of copying genetic material; results in 2 identical copies of
the chromosome.
SISTER CHROMATIDS - identical copies of each chromosome that result from
replication.
3. Gap 2 or G2 PHASE – the cell makes the organelles and substances it needs for cell
division.
II. MITOSIS or CELL DIVISION PHASE - a series of phases in cell division during which the
nucleus of a cell divides into two nuclei with identical genetic material.
CYTOKINESIS - the cytoplasm of the cell divides into two new cells called “daughter cells”
Mitotic Cell Division And Cytokinesis
4 PHASES OF MITOSIS
1. PROPHASE - Sister chromatids CONDENSE to become thicker and visible when viewed
through the microscope.
- The nucleolus and nuclear envelope DISAPPEAR.
- Microtubules that make up the spindle fibers BEGIN TO ASSEMBLE.
2. METAPHASE - The chromosomes are MOVED TO THE CENTER of the cell by the spindle
fibers attached to the centromeres of each chromosome.
- The two sister chromatids of each chromosome are attached to spindle fibers
radiating from opposite ends of the cell.
3. ANAPHASE - The centromeres of each chromosome are PULLED by the spindle fibers
TOWARD THE ENDS OF THE CELL. The sister chromatids are thus separated from each
other.
4. TELOPHASE - New nucleus begin to FORM around the chromosomes at each end of the
cell. The process of mitosis is now complete.
- The cell membrane begins to pinch the cell in two as CYTOKINESIS begins.
THE FINAL PRODUCT: from one parent cell producing 2 daughter cells that are both
diploid and are identical to themselves and parent cell
Control of Mitosis

2. DIFFERENTIATION: Changes that take place in cells as they develop. Cells may develop into
muscle cell, blood cell, heart cell, etc.
GROWTH FACTORS: Are chemicals that stimulate the division and differentiation of new cells
during growth.
REGENERATION: Process of growing back lost body parts.
ASEXUAL REPRODUCTION: Reproduction in which only ONE PARENT produces offspring by
cell division.
1. BUDDING: The formation of a small, budlike cell from larger cell.
2. FRAGMENTATION: Separate pieces of the parent organism can develop into new
individuals.
3. VEGETATIVE REPRODUCTION: New plants grow from the stem, roots, or leaves of
an existing plant.
CANCER: Spread of malignant cells to new locations.
Meiosis and Sexual Reproduction
SEXUAL REPRODUCTION: When chromosomes of TWO PARENTS combine to produce
offspring.
GAMETES: The chromosomes that combine during sexual reproduction are contained in
special reproductive cells.
MEIOSIS: Many organisms produce gametes through a type of cellular reproduction.
Chromosome number
DIPLOID or 2n: Any cell that contains two complete sets of chromosomes.
HAPLOID or n: A cell with only one complete set of chromosomes.
FERTILIZATION: An egg cell and sperm cell of the same type of organism join to produce an
individual.
ZYGOTE: Single cell that results from fertilization.
HOMOLOGOUS PAIRS: Matching pairs of chromosomes in a Diploid.

3. The Phases of Meiosis
I. INTERPHASE
II. MEIOSIS I – homologous pairs of chromosomes separate
1. PROPHASE I - chromosomes CONDENSE to become thicker and visible when viewed
through the microscope. Each homologous pair has a total of 4 chromatids.
- The nucleolus and nuclear envelope DISAPPEAR.
- Microtubules that make up the spindle fibers BEGIN TO ASSEMBLE.
2. METAPHASE I - The homologous pairs are MOVED TO THE CENTER of the cell by
the spindle fibers attached to the centromeres of each chromosome.
3. ANAPHASE I - The homologous pairs are PULLED by the spindle fibers TOWARD
THE ENDS OF THE CELL. The homologous pairs are thus separated from each
other.
4. TELOPHASE I - New nucleus may or may not form around the chromosomes at each
end of the cell.
III. MEIOSIS II - similar to mitosis wherein the sister chromatids are separated, but produce a
haploid chromosome number.
THE FINAL PRODUCT: from one parent cell producing 4 daughter cells that are all
haploid and are NOT identical to themselves and parent cell
COMPARISON: Mitosis vs. Meiosis
MITOSIS MEIOSIS
Chromosome number Diploid or 2n Haploid or n
Identical or not to each other and
parent
yes no
Total number of daughter cells
produced
2 4
What kind of cell All cells except sex cells Only in sex cells
(sperm or egg cells)
GENE: codes for one trait, or characteristics, of an organism.
CROSSING OVER: Exchange of genes between pairs of homologous chromosomes.
Meiosis and Evolution
EVOLUTION: Process of change in living things populations over time.
VARIATION: Differences among members of a population are collectively called variations.