Transcript Genetics Day 1

Cell Growth
and Division
SB1a. Explain the role of cell organelles for both
prokaryotic and eukaryotic cells, including the cell
membrane, in maintaining homeostasis and cell
reproduction.
Essential Question
• Finish the sentence.
– When I cut myself shaving, I began to
bleed. Soon my wound healed. It healed
because my skin cells …….
Cell Division
• Cell division is the process in which a cell
divides into 2 new daughter cells.
1. Before cell division can occur, the
DNA must be replicated.
2. Cell division reduces cell volume thus
making the cell work more
efficiently.
Why Cells Divide?
A. Larger cells need more DNA.
B. Larger cells need more space.
Surface to Volume ratio:
1. Volume increases faster than the cell
membrane (surface area).
The result is the inability to exchange oxygen,
food, and wastes.
** Larger cells are more difficult to maintain.
Chromosome
• In eukaryotic cells,
•
the genetic
information is
carried on structures
called
chromosomes.
Chromosome
numbers are
specific to each
species.
Where are chromosomes
found in the cell?
A.Mitochondria
B.Nucleus
C.Cell Membrane
D.Golgi apparatus
Chromosome Number
Examples
Fruit fly – 8
Humans – 46
Chimpazee – 48
Carrots – 18
Crayfish - 200
Chromosome Structure
• Chromosomes are
•
made of DNA
wrapped around
proteins which are
called histones.
Before cell division,
genetic information is
spread out in thin
thread-like form
called chromatin.
Chromosome Structure
• Just prior to cell division, the DNA in
chromosomes condense and become
visible (with a light microscope).
a. The visible chromosomes consist of 2
sister chromatids.
b. The sister chromatids are attached at a
central point called the centromere.
Chromosome Diagram
The Cell Cycle
Cell Cycle – a series of events that a cell goes
through as they grow and divide.
• It’s divided into the following stages……
– G1, S, and G2,
collectively, are called
interphase.
– In cell division, the
cell divides and splits
with mitosis and
cytokinesis.
The Cell Cycle
• G1 phase (Gap 1) – a period of growth – cell
•
•
•
•
increases in size as they build new proteins.
S phase – (synthesis) – DNA is replicated.
G2 phase (Gap 2) – cell builds organelles
needed for division.
M phase – (Mitosis) – is the orderly division of
the cell’s nucleus.
Cytokinesis – the cytoplasm divides.
Get your Cell Cycle Chains and decorate them.
You also need to write down the cell cycle rap.
It will be useful to you in the next few days.
Cell Cycle Rap
(to the tune of Do Your Ears Hang Low)
Do your cells hang low
Do they reproduce and grow
Interphase lets begin
G1, S, G2 my friends
Then the cell will divide
Now you have 2 nuclei
Do your cells hang low
What is the end product
of the cell cycle?
A.A bigger cell
B.More DNA in one cell
C.A new daughter cell
D.Who knows????
Mitosis
Prophase
Metaphase
Anaphase
Telophase
2 new daughter cells
Prophase
• Prophase1. Chromosomes become
visible because of
continuous coiling.
2. Two centrioles form
out- side the nucleus and
move to the opposite sides
of the cell called poles.
3. Spindle fibers form and
attach to the centromere
of the chromosomes.
4. The nucleolus & the
nuclear envelope
disappear as they begin to
break down.
Metaphase
• Metaphase
•
chromosomes line up in
the middle of the cell
at the area called the
equator.
Remember those
prefixes:
they aren’t going
away!!!
(meta = middle)
middle phase.
Anaphase
Anaphase-chromatids
pull apart and migrate
to opposite poles.
Telophase
• Telophase – final phase of
•
•
•
•
mitosis.
1. Chromosomes disperse
back into chromatin.
2. New nuclear envelopes
form around each pole,
forming 2 new daughter
nuclei.
Spindle fibers and centrioles
disappear.
Each new nucleus develops a
new nucleolus.