Cell Growth and Division Test

What are the limits to cell growth?

1. DNA overload - cells struggle to function properly as they grow larger. 2. Difficulty in transporting materials across the cell membrane - volume increases faster than surface area, diminishing the surface area to volume ratio.

How does cell division address DNA overload?

Cell division helps mitigate DNA overload by copying DNA before the cell splits. And reduces cell volume

What is chromatin?

Between cell division (during interphase) the genetic material

          (DNA) is in the form of chromatin.

         Chromatin is the relaxed form of DNA in the cell’s nucleus

         During cell division, the chromatin condenses to form

             chromosomes.

What are chromosomes?

 i. Made of DNA and protein

        ii. Replicated chromosomes are made up of 2 identical

           chromatids joined together at the centromere.

         iii. Visible only during cell division.

         iv. Human body cells have 46 chromosomes

cell cycle

   i. Interphase- period between cell division

1. G1- period of intense cell growth (organelles)

2. S- DNA replicated

3. G2 preparation for mitosis and high protein production

4. G0—when cells no longer divide, can be permanent or

temporary

What is the M phase?

The M phase refers to the segment of the cell cycle during which mitosis, the division of the nucleus, takes place.

What is the C phase?

The C phase, or cytokinesis, is the process of dividing the cytoplasm resulting in the formation of two unique cells.

What happens during mitosis (prophase)

1. Chromatin condenses into chromosomes

2. Nucleolus and nuclear membrane disappear.

3. Centrioles move to opposite ends of the cell and form

poles. They help to organize the spindle that will move

chromosomes during anaphase.

Metaphase

1. Replicated chromosomes move to the equator of the cell

and attach to spindle fibers at the centromere

Anaphase

.Centromeres divide and sister chromatids move to

opposite

Telophase

A nuclear membrane form around each set of

chromosomes

2. Nucleolus repairs

3. Spindle breaks down

4. Chromosomes lengthen into chromatin

Cytokinesis

division of the cytoplasm

i. In plant cells, a cell plate forms between the two divided nuclei

and separate the plant cell into two cells.

ii. In animal cells, the cell membrane is drawn inward until

cytoplasm is pinched into two equal parts.

iii. Plant cells do not have centrioles but can form spindles.

meiosis

Definition: cell division that produces haploid gametes (single set of chromosomes)

• Haploid: sex cells with a single set of chromosomes

• Number of chromosomes reduced by half

• Consists of Meiosis 1 (4 phases), Meiosis 2 (4 phases)

• Crossing over”

  • Chromosomes exchange DNA

  • Leads to genetic variation

  • For growth, repair, and reproduction

    Creates 4 unique cells

    Gametes

    8 phases (goes through PMAT x2)

    Includes “crossing over” (swaps DNA)

mitosis

Mitosis:

Definition: the division of the nucleus 

• Has 4 phases:

  • Prophase

  • Anaphase

  • Metaphase

  • Telophase

  • For growth and repair

    Creates 2 identical cells

    Body cells

    4 phases (PMAT)

Controls on cell Division

i. Direct cell to cell contact stops cell growth and division

ii. Cyclins are proteins that regulate the timing of the cell cycle in

eukaryotic cells

Cancer

i. Disorder in which some cell lose the ability to control growth

and division

ii. Rapid and abnormal division of cells

iii. Form masses called tumors that damage surrounding tissues

iv. Caused by mutations in DNA

v. Environmental factors that cause cancer are called carcinogens

Apoptosis

i. Some cells go through a process called apoptosis or programed

cell death

ii. Human hands and feet and leaves all contain cells that go

through apoptosis

iii. Also occurs in cells with DNA damage that could lead to cancer

or genetic diseases.

Stem cells

i. Stem cells are unspecialized cells that can develop into

specialized cells under the right conditions.

ii. Scientists believe that stem cells can be used to cure M.S.,

Parkinson’s Disease

Embryonic stem cells

1. Can develop into 210 types of cells

2. Are harvested from an embryo that is 5-8 days old.

3. Pluripotent

Adult Stem cells

1. Are found in umbilical cord blood and bone marrow

2. Can develop into different kinds of cells

3. Multipotent