1. DNA DNA  The common thread of life.

2. What are the functions of DNA?  There are two main functions of DNA –It is the molecule of heredity. –It contains the information needed to construct proteins.

3. What is heredity?  Heredity is the term used to explain the transfer of genetic information from one generation to the next.  You inherited half of your DNA (your genes) from Mom, and the other half from Dad.  DNA is the molecule that allows this to happen.

4. Structure of DNA  As you surely remember the basic building blocks of DNA are nucleotides.  Here we see the phosphate group and 5-Carbon Sugar.

5. Nitrogen bases.  The third part of a nucleotide is the nitrogen base.  There are two types of nitrogen bases: Purines: A and G which have a double ring structure. Pyrimidines: T and C which have a single ring.

7. Genes to Proteins.  Your DNA is housed in the nucleus of every cell in your body.  Most of the time, the DNA is in long twisted strands called Chromatin. Very thin, and cannot be seen using a regular compound light microscope.  The Chromatin condenses to form Chromosomes prior to cell division. These can be seen.

8. Genes to proteins cont.  These strands of chromatin are made up of many genes. A gene can be hundreds or thousands of nucleotides long. (The entire human genome consists of 3 BILLION nucleotides).  Each gene is a series of nucleotides which contains the information to make a protein.  1 gene = 1 protein.

9. The genetic code  Genetists (Scientists who study genetics) were interested in determining how information in your genes was used to create proteins.  They knew that there were 20 different amino acids and that there were 4 types of nucleotide.

10. Cracking the code.  Since there were twenty amino acids and only 4 nucleotide types, they knew that the genetic code had to consist of more than one nucleotide. 4 1 = 4 4 1 = 4 Ex. The nucleotide Adenine by itself does not code of the amino acid Threonine.

11. Cracking the code (cont.)  By applying the same logic, they realized that the genetic code could not consist of two nucleotides either. 4 2 =16 Adenine and Cytosine together does not code for the amino acid Threonine. Adenine and Cytosine together does not code for the amino acid Threonine.

12. Cracking the code  Expanding on the theme, they realized that sequences of 3 nucleotides would give more than enough combinations to code for all 20 amino acids. 4 3 =64 4 3 =64 Adenine, Cytosine and Guanine DO code for the amino acid Threonine. They call these 3-nucleotide sequences CODONS. We will be using the actual genetic code later in this unit.

13. The Genetic Code Lets take a look. DNA genetic code DNA genetic code

14. DNA Replication  Prior to cell division (mitosis or meiosis) the cell must make another copy of, or replicate it’s DNA.  The DNA molecule basically unzips itself by breaking the hydrogen bonds holding the two strands of nucleotides together.  Each strand then forms a second strand by using free nucleotides which are found in the nucleus.  DNA replication simple DNA replication simple DNA replication simple  DNA replication complex DNA replication complex DNA replication complex

15. DNA and RNA  Both are nucleic acids, and are very similar to each other.  There are some differences. DNA RNA DNA RNA Sugar: Deoxyribose Ribose Strands: 2 1 Nitrogen Base: Thymine Uracil LocationNucleus Nucleus &Cytoplasm

16. RNA transcription  While DNA contains an entire library’s worth of information, it is a big, big molecule.  It is so big, it cannot fit through the pores of the nuclear membrane.  To get the information needed to make proteins to the ribosomes, the DNA needs some help.

17. Enter the messenger  In order to get the information stored in a gene to the ribosome, messenger RNA (mRNA) is transcripted.  First, the DNA will partially unzip itself to expose one gene’s worth of code.  An enzyme called RNA polymerase then copies a strand of RNA based on the template strand of the DNA.

18. mRNA transcription  RNA transcription simple RNA transcription simple RNA transcription simple  RNA transcription complex RNA transcription complex RNA transcription complex