Download Cell Cycle - Madison County Schools

Cell Cycle
I. Cell Cycle
• The cell cycle is a series of events in
eukaryotic cells that leads up to cell
division.
• Cells grow, duplicate, and divide.
4 Stages
• 1. Gap 1 (G1)
• 2. Synthesis (S)
• 3. Gap 2 (G2)
• 4. Mitosis (M)
2 Processes
• The Cell Cycle occurs in two processes:
• 1. Interphase- G1, S, G2
• 2. Mitosis- Mitosis and Cytokinesis
Interphase
• G1- cell carries out normal functions. Cell has
proteins to “check” the cell and make sure it is
ready for synthesis. Organelles increase in number.
• S- cell copies its DNA.
• G2- cell carries out normal functions and grows.
The cell has checkpoint proteins to check that the
DNA is undamaged and the cell is the right size.
Mitosis
• M- nuclear membrane dissolves, DNA
condenses to form chromosomes, two new
nuclei form.
• Cytokinesis- process that divides the cell into
two new daughter cells.
• Parent cells and daughter cells are identical!
Cell Cycle
Cells are Controlled
• Surface area to volume ratio in cell means that as a
cell increases in size, the volume increases faster
than the surface area.
• Contact Inhibition- cell growth is ceases when
two cells come in contact with one another.
Cells are Controlled (cont.)
• Growth must be
controlled and
organized.
• If cell division becomes
uncontrollable, cancer
occurs.
• Tumor- is an organized
clump of uncontrollably
dividing cells.
II. Mitosis and Cytokinesis
• Chromosome- is a long strand of DNA that
forms an “X” shape.
• 46 chromosomes are in the human body.
DNA During Interphase
• DNA wraps around Histone Proteins. These
proteins make DNA condense.
• During interphase, DNA forms chromatin.
• Chromatin- is the “loose” combination of DNA
and protein. “Loose” refers to how DNA folds
in on itself.
DNA at the Beginning Mitosis
• DNA tightly condenses into the characteristic
“X.” This is very visible under a microscope.
• Chromatid refers to one of the sides.
• The sides are identical.
• Centromere is an area of condensed
chromosome that holds the chromatids
together.
• Gene- segment of a chromosome that codes
for a specific protein.
Phases of
Mitosis
Prophase
• Chromatin condenses
into tight
chromosomes.
• Nuclear membranes
disappear.
• Centrosomes go to
opposite ends of the
cell and spindle fibers
form.
Metaphase
• Spindle fibers attach
to the centromere
on each
chromosomes.
• Chromosomes align
on the cell’s equator
Anaphase
• Spindle fibers shorten and
pull the chromatids away
from one another.
• Sister chromatids separate
from each other into
daughter chromatids.
• Chromatids go to opposite
ends (poles) of the cell.
Telophase
• Complete set of
chromosomes are at
each end (poles) of the
cell.
• Nuclear membrane
starts to form.
Cytokinesis
• Cell divides into two identical daughter cells.
• Cell Cycle is complete.
• In animal cells, a furrow or trench is formed. The
membrane gradually pinches closed.
• In Plant cells, a cell plate is formed between the
two nuclei and a cell wall is formed from
cellulose.
Animal vs. Plants
III. Reproduction
Two Types:
• 1. Asexual- the creation of genetically identical
offspring from a single parent by mitosis.
• Ex. Binary Fission- asexual reproduction by a
single celled organism. The cell divides into
two identical parts.
• 2. Sexual- fusion of two gametes that creates an
offspring that is a genetic mixture of both parents
by meioses.
Specialized Cells
• Somatic Cells- are body cells. They make up
most of the body tissues and organs.
• Germ Cells- are cells in the reproductive
organs.
– Gametes- are the sex cells.
–Ex: Sperm and ova (eggs)
Chromosomes
• Cells have 46 chromosomes or 23 pairs (one from
the mother and one from the father).
• Homologous Chromosomes- refers to the pairs of
chromosomes.
• 22 of the chromosomes are autosomeschromosomes that define characteristics.
• 1 sex chromosome that controls the
development of sexual characteristics.
Sex Chromosomes
• Humans have two different sex
chromosomes:
–X and Y
• Females are XX
• Males are XY
Meiosis
• Meiosis- is when the cells divide and the
chromosome number cuts in half.
• Sex cells go from Diploid Cells (46 chromosomes) to
Haploid Cells (23).
• Diploid also known as 2n and haploid known as 1n.
• N= chromosomes and # = chromosome amount
Meiosis I
• 1. Prophase I- nuclear membrane breaks down,
the centrosomes move to opposite poles, and the
chromosomes condense into pairs.
• 2. Metaphase 1- the pairs of chromosomes line
up along the midline of the cell.
• 3. Anaphase 1- pairs of chromosomes move to
opposite poles.
• 4. Telophase 1- the nuclear membrane can
reforms and the cell starts to divide.
• 5. Cytokinesis- two new daughter cells form
Meiosis I
Meiosis II
• 6. Prophase II- The nuclear membrane breaks
down, centrosomes move to opposite poles, and
spindle fibers form.
• 7. Metaphase II- 23 chromosomes align along the
equator.
• 8. Anaphase II- sister chromatids are pulled apart
from each other and move to opposite poles.
• 9. Telophase II- nuclear membranes form around
each set of chromosomes.
• 10. Cytokinesis- nuclear membranes form around
the chromosomes at the poles.
Meiosis II
Outcomes
• Cells went from DIPLOID to HAPLOID.
• Diploid (2n)- cell has two copies of each
chromosome. One from mother and one from
father. This refers to the 46 Chromosomes.
• Haploid (1n)- cell only has one copy of each
chromosome.
– Now there are 23 chromosomes in the cell.
– 22 are autosomes and 1 is a sex chromosome.
Mature Sex Cells
• Gamete- are mature sex cells. Ex: sperm and
egg
• Gametogenesis- is the production of gametes.
• Sperm- male gamete
• Egg- female gamete
Difference Between Sperm and Egg
Sperm and Egg
• Sperm production = 4 sperm
• Egg Production = 1 Egg + 3 Polar Bodies
• Polar Bodies- are cells that are mainly DNA.
The polar bodies cannot survive and are
broken down.
• Once fertilized, the sperm and egg form
a diploid cell (2n).
Crossing Over During Meiosis
• Crossing over recombines genes and causes
genetic variation.
• Crossing Over- is the exchange of
chromosome segments between homologous
chromosomes during prophase I of Meiosis I.
• Chromosomes are very close together. A
segment of chromatin breaks off and
reattaches to another chromosome.
Crossing Over
QR Mitosis Activity Pictures
• Use the following slides to make up the QR
Mitosis Activity.
Station 3
Station 5
Station 1
Station 2
Station 4
Station 6
• http://www.youtube.com/watch?v=IeUANxFV
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