Download Cell Division

Review last week
DNA Structure
• Nucleotides have:
– A sugar molecule
– A phosphate molecule
– A nitrogenous base molecule
DNA Structure
Each nucleotide has one of four different
nitrogenous bases
– Adenine (A), Thymine (T), Cytosine (C), Guanine (G)
• Which bases pair together?
– A with T (vice versa)
– C with G (vice versa)
The Genetic Code
• DNA has a _______-character code, which
form _______________(i.e. GGC)
• Each 3 letter word codes for the production of
one of 20 different amino acids
Definition
• These are a short section of DNA that contains
instructions to make a specific protein
– GENES
The Cell Cycle
The Cell Cycle
• At any moment, there are millions of cells
going through cell division
• But what about the trillions of cells that
aren’t? What are they doing?
• They are in some phase of the Cell Cycle
The Cell Cycle
The Cell Cycle
• The cell cycle is a sequence of events in the
cell from one cell division to another.
• The growing and working phase of the cell is
called interphase
The Cell Cycle
• A cell is in interphase for 90% of the total time
of the cell cycle.
• During interphase a cell will:
– Make copies of each organelle
– Make copies of chromosomes (DNA)
• Each chromosome and its copies = sister chromatids
Cell Division
Cell Division
• What needs to happen in order for cells to
divide?
– DNA needs to copy itself (chromosomes)
– Chromosomes
• Thread-like structures containing DNA
Cell division
• There are two types of cell division:
• Mitosis
• Meiosis
Mitosis
• One cell splits into two identical daughter
cells
What is mitosis for?
• Mitosis is used to produce new body
cells (eg. for growth and repair).
• Simple plants and animals can also
use mitosis to reproduce
• This is called Asexual reproduction
What happens before mitosis?
1. The chromosomes get thicker
What happens before mitosis?
2. The chromosomes are replicated and can
now be seen as x-shapes
What happens in mitosis?
3. The nuclear membrane disappears. The
chromosomes line up on the spindle. The
chromosomes are pulled to opposite ends
of the cell
What happens in mitosis?
4. Each new cell is IDENTICAL to the
original and has THE SAME number of
chromosomes
Mitosis
The stages of mitosis are:
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
*Each stage has specific details about what is
happening to the cell during mitosis
Cytokinesis
• Cytokinesis is the second process of cell
division
• It divides the cytoplasm into two daughter
cells
Question 1
• If a cell with 28 chromosomes divides into
2 new cells, how many chromosomes will
each new cell have?
– 28 chromosomes
Question 2
• True or False . . .
The cells produced in mitosis are
genetically identical
• TRUE