The NucleusAsexual Reproduction:

Mitosis &

Cell Division

General Info:

Nucleus:

–the “brain” of the cell

–controls the cells activities

–responsible for cell division, protein synthesis

General Info Cont.

Nucleus:–contains genetic material called

DNA

–DNA long chain (chromatin) of genetic information (eukaryotes)

–In prokaryotes (bacteria) DNA is in the shape of a ring called a

plasmid

Chromatin

Nucleolus

Nucleus

Chromosomes:

–made of Deoxyribonucleic Acid DNA wrapped around proteins

–Chromosomes in eukaryotes are “rod shaped” structures made of DNA and proteins

Chromosomes:

• consist of 2 halves called chromatids

• “sister chromatids” are connected in the center by a centromere

Chromosome

(Coiled chromatin)

Ck question

Topic: DNA and Chromosomes

Date: 1-4-2010

1. Genetic material of a cell is called …

2. The location of #1

3. The ring of DNA found in Bacteria is…

4. Chromosomes consist of 2 halves known as…

Chromosome Numbers:

• Each species has a characteristic number of chromosomes in each cell.

• ex. Fruit flies (drosophila) = 8

chromosomes

• horse has 64 chromosomes

• humans have 46 and chimpanzees have 48 chromosomes

From 7 characteristics of living things:

All living things Grow

• Growth occurs from the division of cells.

• Cell Division (cellular reproduction) allows cells to:

1.Grow in size

2.Grow in number

3.Replace worn out, injured or dying cells

2 Forms of Cellular Reproduction (cell division):

1. Asexual Reproduction involves only one parent cell

a. Occurs in Autosomes or somatic cells … body cells

b. Plants/animals

2 Forms of Cellular Reproduction (cell division) Cont…

c. protists (protozoan) = single celled organisms

(binary fission)d. fungi

e. bacteria = binary fission

2 Forms of Cellular Reproduction (cell division):

2.Sexual Reproduction

involves 2 parents cellsa. Gametes = sex cells

b. Making gametes!!!

Sexual reproduction:

Occurs in sperm cells and egg cells

The Cell CycleAsexual Reproduction aka MITOSIS

The Cell Cycle is responsible for:

– birth and death of a cell– Cell division of nucleus, home of

hereditary information…chromosomes

– Cell division (Cell Cycle) consists in 3 processes

Cell Cycle consists in 3 processes

1. Interphase2. Division of the nucleus=

mitosis3. Division of the cytoplasm = cytokinesis

Ck questionTopic: Cell reproduction

Date: 1-4-2010

1. How many chromosomes does a normal humans have?

2. Identify 3 reasons cells divide.

3. The 2 types of cellular reproduction are…

4. Define gametes.

5. Define autosome.

Before a cell divides….

Interphase (nucleus)

• Cell spends most time here

Interphase:• Divided into 3 phases

1. G1 – cells grow to mature size

2. S – DNA is copied or duplicated

called DNA replication

1. G2 – cell prepares to divide

• Some cells have a G0 phase, they do not replicate after maturity. Ex. Nervous System

Mitosis:

One cell (PARENT CELL) divides into

2 identical cells (Daughters) – divisions: nucleus divides

– a series of chronological steps:

1. prophase

2. metaphase

3. anaphase

4. telophase

Division of the nucleus (DNA)!!

Mitosis

Prophase:

• Chromatin condenses, becomes visible strands of DNA called chromosomes

• 2 chromosomes are made of “sister chromatids”

• chromatids are connected by centromere

• centrioles in animal cells begin to separate (opposite ends or poles)

Prophase Cont.

• spindle fibers form (football shape) from the centrioles and connect to centromere of each chromatid

• nuclear membrane fades

• chromatids (chromosomes) begin moving to center

CentriolesSpindle fibers

Chromosomes Centromere

Metaphase: (middle)

• chromosomes (chromatids) line up in the middle of the cell

• centromere divide

• chromosomes are pulled apart separate chromosomes (???)

Chromosome

Centromere

Spindle fibers

Anaphase: (away)

• centromere divides

• chromatids separate

• move to opposite ends of cell

• complete set of chromatids go to each pole

chromatid

Telophase:

• final step of mitosis

• chromatids unwind, spindle fibers disappear

• nuclear membrane forms around each of chromatids

Cytokinesis:

• final step in the cell cycle

• cytoplasm (and organelles) divide equally in cells

• animals-pinching in of the cell membrane forming a cleavage furrow

• plants - cell plate forms across the middle growing outward

In animal cells

• (begins outside the cell)

In plate cells

• (begins inside the cell)

Results of Mitosis:• division of the nucleus (Asex. Reprod.)• products are 2 new cells with identical

information to each other and to the parent cell

• most cells reproduce asexually mitosis– ex. Of cells produced through mitosis

include:

in animals: blood cells, skin cells, cheek cells,

in plants: root cells, stem cells, leaves

Parent Cell

Identical Daughter Cells

Identical Daughter CellsIdentical Daughter Cells

Parent CellParent Cell

Two identical Two identical daughter daughter

cellscells

• mitosis