Page 198 Write out definitions for Key Terms
Chapter 6
A Closer Look at Cell Division
Section 6.1
Pages 176 - 178
DNA - The Genetic Material
- Deoxyribonucleic Acid (DNA) refers to the genetic information found in the chromosomes of all cells.
- the DNA determines how the cell functions and reacts with its surroundings.
- the DNA tells the rest of the cell how to divide, repair itself, react with other cells, and adapt to changes in it's environment.
- special messengers send these messages from the DNA in the nucleus to the organelles in the cytoplasm.
- DNA uses a four-character code made up of nitrogen bases.
A - Adenine T - Thymine C - Cytosine G - Guanine
- these letters are arranged in orders called codes.
- these codes are arranged into three character sequences ("words") which are called genes.
See Diagram 6.1 DNA Molecules
DNA Replication, Genes, Variation
- these DNA stories determine a characteristic such as hair colour, eye colour, skin colour and all other instructions which make you unique.
- this "language of life" is stored in the 6 billion nitrogen bases of DNA in about 100,000 genes in 46 human chromosomes.
- genes which determine eye, hair, and skin colour are called recessive genes. This means that they can skip generations.
- each human cell has 46 chromosomes arranged in 23 pairs. Each pair has one chromosome from the mother and one from the father.
- before cells divide the genetic material makes a duplicate of itself so that during cell division each cell has its own complete set of genetic information.
DNA Fingerprints
- unless you have an identical twin your DNA is unique to you. Only your fingerprints would be different.

- you may change your appearance as much as you like but your DNA will always be the same.
- Because of this uniqueness, DNA fingerprinting is now widely used in the courts.
See Figure 3 Page 178.
Section 6.2
DNA, Mutations, and Cancer
- DNA is floating in a solution containing many chemicals, some of which come from outside the cell. DNA may be exposed to the sun or to viruses which can cause changes in the sequence of the nitrogen bases.
- these changes in the genetic code are called mutations.
Most of these mutations are either neutral or harmful. The harmful mutations cause cancer.
Cancer
- cancer occurs when cell division goes out of control. It is actually a group of diseases associated with unregulated cell division. These cells divide much quicker than they should.
- any substance or energy that causes cell mutations in the genes regulating cell division are called carcingens.
Cancer Cells
- normal cells cannot divide when isolated. They must be able to communicate for normal cell division. Cancers cells can divide when isolated. Cancer cells grow so quickly that they can crowd and damage other cells.
- as cells mature they specialize and become whatever is needed - bone cell, skin cell, nerve cell.
Cancer cells do not change shape as they mature. This makes them inefficient and they use up energy and resources needed by normal cells.
Page 182 -183 Activity 6.3.
- Do questions 1 – 3 and questions 2 & 3 from Understanding Concepts. This is to be passed in for marking.

Section 6.9
Cloning
Pages 194 - 197
1. Define the term cloning.
2. How do the vast majority of organisms produce exact duplicates of themselves?
3. Why are clones identical to their parent?
4. Cloning is what type of reproduction?
5. What were the names of the scientists that experimented with animal cloning using frogs?
6. What is an "enucleated" cell?
7. Who was Dolly?
8. Who conducted the experiment that produced Dolly?
9. Explain the experiment.
10. Draw a diagram of the process and the outcome of the experiment.