2/26 Objective: Explain the structure and function of DNA and the process of Replication. DMA: Read the O.J. Simpson- A Mountain of Evidence article on page 324 (Chapter 9)

The Structure and Function of DNA

It is passed from generation to generation. 1. DNA is our genetic code!!! It is passed from generation to generation. It carries information that controls the functions of our cells. DNA stands for deoxyribonucleic acid  

Every nucleotide has three parts: 3. DNA’s Structure: a) It is a polymer made of nucleotides! Nucleotides: building blocks of the DNA molecule. Every nucleotide has three parts: 1. sugar group 2. phosphate group 3. nitrogenous base  

Question #2: What three parts make up a nucleotide?

Thymine (T) Cytosine (C) Guanine (G) ***The only variation among the nucleotides is what base is attached to each.   b) The four nitrogenous bases in DNA are… Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

c) The shape of a DNA molecule is a double helix c) The shape of a DNA molecule is a double helix. Sugar and phosphate Bases *Bases form the rungs of the ladder. *Sugars and phosphates form the sides of the ladder.

d) Other important information: Chargaff’s Rule: in every DNA double helix the #A = #T and the #C = #G. Example: -A-G-C-A-A-T-C-T-G- -T-C-G-T-T-A-G-A-C-

e) Chargaff’s rule teaches us that… adenine always bonds to thymine. guanine always bond to cytosine.

-A-C-G-T-C-C-G-A-A-T- Question #4: What is the complimentary strand of DNA that would attach to the strand below? -A-C-G-T-C-C-G-A-A-T-

Be able to identify… -the deoxyribose groups -the phosphate groups -the nitrogenous bases -the hydrogen bonds

information for making one particular thing (protein) by the cell. 4. Genes: Sections of DNA that hold the information for making one particular thing (protein) by the cell. Examples of information contained on one gene: *making the enzyme for fat digestion *making the enzyme for starch digestion *protein for eye color etc…..etc…..etc!

5. Chromosomes: Bundles of DNA that are made up of genes that carry information for the entire cell. a) Humans have 46 chromosomes in each cell that hold about 25,000 genes. Human Chromosomes

Question #5: What is a chromosome?

Question #6: Describe this diagram in words. Nucleotides DNA Genes Chromosomes

Human Genome The order of bases on all 23 pairs of human chromosomes. This allows us to know the specific location on a chromosome at which the DNA codes for a specific protein.

DNA Replication DNA Replication – When DNA makes a copy of itself! 2 complete and identical sets of genetic information are produced. The cell does this process before it divides

Step 1: a. Enzymes begin to unzip the. double helix. B Step 1: a. Enzymes begin to unzip the double helix. B. Hydrogen bonds are broken C. This process proceeds in 2 directions at the same time.

Step 2: Each existing strand of the DNA molecule is a template for a new strand. Free-floating nucleotides pair up with exposed bases on each template strand. DNA polymerases bond these nucleotides together to form new strands.

Vocab: DNA polymerases Enzymes that form bonds between nucleotides during replication.

Step 3: 2 identical double-stranded DNA molecules are produced. Each DNA molecule contains an original strand and one new strand.

Replication is fast and accurate In human cells, about 50 nucleotides are added every second to a new strand of DNA at the point of replication. DNA polymerase “proof-reads” DNA sequences and replaces bad nucleotides.