1. Science 9

2.  Students will be expected to:  Explain the importance of using the terms gene and chromosome properly

3.  The cells of all living things contains DNA  It is a chemical compound that is responsible for genetic information  Deoxyribonucleic acid  Provides directions that guide the well being of the cell  Information gets sent from the nucleus to other parts of the cell by chemical messengers

4.  It is made up of a series of chemicals called nitrogen bases, held in a long, winding helix  They are used like letters or characters in a simple code  There are four characters, or nitrogen bases, that make up DNA: adenine (A), thymine (T), cytosine ©, and guanine (G)  The order in which they appear is the code  Groupings of three bases help to determine the genetic make up of an individual

5.  A gene is a section of DNA that determines a trait or characteristic  In humans, there are over 6 billion nitrogen bases of DNA

6.  DNA can make copies of itself in a process called replication  Cells need to be able to divide in order to replace dead and worn out cells  The DNA duplicates itself before a cell divides  Each cell has a copy of genetic information

7.  When replicating, the DNA molecule “unzips” and each side serves as a place to receive a nitrogen base  Adenine always pairs with thymine  Cytosine always pairs with guanine  By the end of the process, two helixes are formed  The two new DNA molecules are identical to each other

8.  Humans have 46 chromosomes arranged in 23 pairs  One chromosome comes from each parent  The information on one chromosome may be slightly different from the information of the other chromosome (differences in the code)

9.  The DNA contained in your chromosomes is unique to you  DNA is one way to identify yourself since no one (except an identical twin) has all the same DNA as you