Cell Reproduction

1
Cell Reproduction

• Chapter 10, 11-4

2
Cells Grow!

• Living organisms are made of cells. Like living
  organism, cells also go through periods of
  growth, and ultimately divide to produce more
  cells.
• Cell growth is limited by
• DNA overload
• Information/material exchange

3
Cell Division

• Chromosomes
• Condensed chromatin
• During the cycle of a cell, chromosomes appear as
  X during mitosis.
• These X-shaped chromosomes are made up of a pair
  of identical chromosomes, each called a
  Chromatid.
• The chromatid are attached at a point called the
  Centromere.
• During the life of a cell it follows a number of
  set steps that occur. These steps are called the
  Cell Cycle.

4
Chromosomes

• Each organism has a set number of chromosomes in
  its cells.
• Humans for example have 46 chromosomes
• Flies have 8
• There are 2 types of cells
• Autosomal Non-sex cells. The cells in the rest
  of the body.
• Gamete Cells involved in sexual reproduction.
• Haploid vs. Diploid
• The total number of chromosomes in these 2 types
  of cells differ. In autosomal cells 2 sets of
  chromosomes exist.
• In the sex cells (gametes) only 1 set of
  chromosomes exist.

5
Chromosomes

• In Humans
• 23 unique chromosomes (Haploid number 23)
• In autosomal cells 46 chromosomes total OR 2
  pairs of the 23 unique chromosomes.
• In gametes 1 set of the unique 23 chromosomes.

6
Cell Cycle

• 2 Major phases to the Cell Cycle
• Occurs in somatic cells of organisms.
• Interphase in-between period
• Mitosis period of cell division
• The result of the cell cycle are 2 identical
  cells called daughter cells.

7
Cell Cycle

• Mitosis and Interphase have subphases. In these
  subphases specific events occur.
• Ultimately there needs to be an equal division of
  the cell contents in order to produce 2 healthy
  cells.

8
Mitosis

• Mitosis begins with one adult cell.
• Through a series of steps, this adult cell spits
  into 2 identical daughter cells.

9
Interphase

• Has 3 major subphases.
• G1, S, and G2

10
Interphase

• In G1 of Interphase the cell grows normally and
  performs its regular functions
• In the S phase the DNA is replicated (double the
  DNA)
• In G2 the cell makes ready to divide.

11
Mitosis

• Within the mitosis phase, there are 4 major
  subphases.
• Each phase is clearly visible and has defining
  features.

12
Prophase

• This is the longest of the 4 mitosis phases.
• In animal cells the centrosomes form on either
  side of the chromosomes.
• Spindles (microtubules) attach the chromosomes to
  the centrosomes
• The chromatin condenses to chromosomes.
• The nuclear envelope and nucleolus disappear.

13
Metaphase

• Most obvious of the mitosis phases.
• Chromosomes line up in the center of the cell
  (called metaphase plate).
• Each chromosome is attached by spindle fibers to
  both centrosomes.

14
Anaphase

• The sister chromatids are separated by the
  pulling centromeres.
• The chromosomes continue to move until they reach
  opposite polls of the cell.

15
Telophase

• The daughter cells begin to separate along the
  metaphase plate.
• The chromosomes disperse into chromatin.
• Meanwhile, the nuclear envelop begins to reform.
  As does the nucleolus.
• The spindle fibers start to break apart.

16
Cytokinesis

• Occurs during Telophase!
• Animal Cells
• cell membrane pinches inwards
• Plant Cells
• Cell plate is formed from Golgi in cell membrane
• Cell wall forms between this
• Cell Plate Formation

17
Regulating the Cell Cycle

• Controls of Cell Cycle
• Cells can only divide a certain number of times.
• Cells stop dividing when they come in contact
  with other cells (Known as Contact Inhibition).

18
Regulation of Cell Cycle

• Regulators of the Cell Cycle
• A group of proteins known as cyclins regulate the
  timing of the events of the cell cycle.
• Internal Regulators proteins within the cell
  that respond to events, such as DNA replication,
  alignment of chromosomes.
• External Regulators proteins that respond to
  events outside the cell. Signal the cell to speed
  or slow down the cycle.

19
Cancer

• When cell cycle regulation goes wrong, the result
  is the formation of cancer.
• Cancer cells are those that continuously divide,
  and ignore Cell Cycle regulation signals.
• Cancer is caused by altering the regulators of
  the cell cycle. Many substances such as tobacco
  smoking, virus infections and radiation have lead
  to disruption of growth controlling proteins.

20
Cancer

• Cancer is caused by a number of mutations within
  a cell. It is not a one hit wonder!