Transcript mitosis and cell cycle chs

Cell Cycle & Mitosis
Cell reproduction
• Unicellular:
– asexual reproduction
• Multicellular:
– Somatic (body cells)
•
Mitosis:
– Cell division
– process of growth and repair
– Gametes (sex cells)
•
Meiosis:
– Reproduction
– production of sex cells
To understand reproduction and cell division,
one must understand what happens to the
chromosomes (DNA) inside the cells.
What are chromosomes?
Nucleus of the cell
cell
chromosome
 Made up of DNA
 Found in nucleus
 Carriers of genetic information
Animation:
http://www.johnkyrk.com/chrom
mestructure.html
• Usually DNA exists as chromatin which are long,
winding strands that condense into chromosomes
before dividing
• Chromosomes are made up of two chromatids which
are held together with a centromere
centromere
chromatids
chromatin
Duplicated DNA and
sister chromatids
chromosome
GENOME
• Is the full set of chromosomes
in a diploid cell
• Diploid cells are somatic cells
(2n), or have two copies of
each chromosome in its
genome.
• Haploid cells are sex cells (n),
and have only one copy of
each chromosome.
• Humans have 23 pairs or 46
chromosomes (2n) in their
somatic cells
• Humans have 23 chromosomes
(n) in their sex cells
CHROMOSOME
GENOME
GENE
BASE PAIRS
The cell cycle
 Is the sequence of growth and
division in the cell:
1. Interphase: is the growth period
where DNA is copied; includes G1,
S, and G2
G1: growth phase
S: copying of chromosome
G2: getting ready to divide
G0: Cells in resting state
2. M-phase: dividing period producing
two new cells; includes mitosis &
cytokinesis
MITOSIS
• division of cells
producing two cells
with the same number
of chromosomes
• Happens in M-phase
of the cell cycle
• It has 5 steps
(interphase and
cytokinesis are not
part of mitosis)
THE ENTIRE CELL CYCLE
Prophase
• Longest phase of mitosis
• Chromatin coils into
chromosomes
• The nucleus disappears
• Centrioles form and move to
opposite poles of cell
• Spindle fibers form from
centrioles and begins to cross
cell
Metaphase
• Chromosomes line up
in the middle of the
cell
• Spindle now forms
across the cell
Anaphase
• Spindle fibers begin
to shorten
• This pulls
chromosomes apart
• Now the chromosome
halves are referred to
as chromatids
Telophase
• Chromatids reach poles
• Chromosomes unwind
into chromatin
• Spindle fibers break
down
• Nucleolus and nuclei
reform
• Plasma membrane
begins to pinch in
Cytokinesis
• Division of cytoplasm
• In animal cells: cell
membrane continues to
pinch in until two cells are
formed
• In plant cells: cell plate
forms in center of cell and
eventually splits cells
• At the end of mitosis, two
new cells are produced;
called “daughter” cells
Animation:
http://www.johnkyrk.com/mitosis.html