Unit 3: Chapter 10 Mr. DiBiasio

Question?  When a living thing grows, what happens to its cell? Does an animal get larger because each cell increases in size or because it produces more cells?

All Living Things Grow and Develop …  Growth means an increase in cell number, not size.

Limits to Cell Growth  There are two main reasons why cells divide rather than continuing to grow: 1) the larger a cell becomes, the more demands the cell places on it DNA 2) the cell has more trouble moving enough nutrients and wastes across the cell membrane

DNA Overload DNA is what controls a cell’s function and is located in the nucleus When a cell gets larger it does not make extra copies of DNA This puts extra pressure on the DNA and causes it not to function properly

Cell Division To stop the cells from becoming too large, a growing cell divides forming two “daughter cells”. This process is what is known as Cell Division Before Cell Division occurs, the cell replicates, or copies, all of its DNA. Each Daughter Cell will get its own complete set of genetic information

Reproduction Parents produce a new generation of cells or multi-celled individuals like themselves Parents must provide daughter cells with hereditary instructions, encoded in DNA, and enough metabolic machinery to start up their own operation

Chromosomes 1. In Eukaryotic cells, chromosomes carry the genetic information that is passed on from one generation of cells to the next. 2. Chromosomes are made up of DNA, which carries the cells coded genetic information- and proteins. 3. The cells of every organism have a specific number of chromosomes.

Chromosomes 7. Because of this, each chromosome consists of two identical, “ sister ” chromatids.

Human Chromosome Number  Diploid chromosome number (n) = 46  Two sets of 23 chromosomes each One set from father One set from mother  Mitosis produces cells with 46 chromosomes--two of each type

Cell Division Mitosis Division of the nucleus Cytokinesis Division of the cytoplasm

Process of Mitosis  Mitosis Cell reproduction in which two genetically identical cells are made from one cell.

Which Cells undergo Mitosis?  Body Cells Cells that make up the body Examples: skin, hair, blood, bones, nerves, muscle, etc.

Cell Cycle

Interphase  Usually longest part of the cycle  Divided into 3 phases (G1, S, G2)  Cell increases in mass  DNA is duplicated

Mitosis  Period of nuclear division  Usually followed by cytoplasmic division  Four stages: Prophase Metaphase Anaphase Telophase

Prophase  Centrosomes move toward opposite poles.  Spindle fibers form.  Nuclear envelope breaks down.  Chromatids are attached at the centromere.  Nucleolus disappears.

PROPHASE

Metaphase  Chromosomes line up across the center of the cell.  Spindle fibers attach to each chromosomes at their centromere

METAPHASE

Anaphase  Centromeres split.  Sister Chromatids move toward opposite poles.

ANAPHASE

Telophase  Chromosomes disperse.  Spindles break apart.  Nuclear envelope re-forms around each group of chromosomes.  Nucleolus becomes visible in each daughter nucleus.  Mitosis Ends

TELOPHASE

Cytokinesis Division of the cytoplasm  Usually occurs with Telophase  In animal cells, the cytoplasm is pinched inward, forming a cleavage furrow.  Plant cells form a cell plate, which forms from the inside out.

Uncontrolled Cell Growth  What happens to cells that do not respond to signals that regulate growth?  Cancer a disorder in which some of the body’s own cells lose the ability to control growth. A disease of the cell cycle

Cancer  Cancer cells don’t respond to signals that regulate growth  They divide excessively and form masses of cells called tumors  They can break loose and spread throughout the body.

Cancer  One in three people will develop cancer.  One in four people will die of cancer.  More than 1500 Americans died each day of cancer this year.  Over 1,000,000 cases of skin cancer will be diagnosed this year.  Cancer is the leading cause of death among Americans under the age of 85.

What causes cancer cells?  Cells are transformed By chemicals, certain viruses, and X-rays  If these cells are not destroyed, they divide and form a mass of abnormal cells called a tumor

Progression of Cancer NORMAL CELLS BENIGN fast dividing cells, not really toxic, only cause mechanical damage MALIGNANT toxic, cause local toxicity and inflammation METASTATIC travel from one place to another. The real killer

Treatments  Surgery – remove the affected cells  Radiation – high-dose X-rays kill cells  Chemotherapy – drugs kill cells  Hormone therapy – hormones stop cell growth

What causes cancer cells?  Cells are transformed  What can cause cells to be transformed? (carcinogens) Chemicals ○ Tobacco, pesticides X-rays (radiation) UV light Family History Viruses ○ HPV (human papillomavirus), increases risk of cervical cancer.