DNA Deoxyribose Nucleic Acid – is the information code to make an organism and controls the activities of the cell. –Mitosis copies this code so that all the new cells gets the same information. Watson and Crick are the famous scientists that discovered what DNA looked like.

- Cell Division Shape of DNA The DNA molecule is shaped like a twisted ladder also known as a double helix.

The Structure of DNA Nucleotides: a monomer of DNA made up of a 5-carbon sugar (Deoxyribose), phosphate group and a nitrogen Base.

Four nitrogen bases –Adenine (A) –Guanine (G) –Cytosine (C) –Thymine (T) What bonds together? –Adenine = Thymine –Guanine = Cytosine

The backbone of DNA is formed by the sugar and the phosphate groups. The Nitrogen bases stick out from the sides of the backbone making up the steps of the ladder. Backbone Nucleotide Nitrogen Base

Quiz What is the shape of the DNA molecule? What are Chargaff’s Rules? What are two differences between DNA and RNA? What are the three types of RNA? Which scientists came up with the structure of DNA? Where are the following located: mRNA, DNA, Ribosomes?

How Replication Occurs DNA Replication is carried out by a series of enzymes. –These enzymes “unzips” a molecule of DNA and allows for the formation of the new strands –DNA polymerase: is the main enzyme involved because it joins individual nucleotides to produce the DNA molecule, along with “proofreading” the new strand.

Replication of DNA Replication: is the process by which DNA is duplicated. –The DNA ladder breaks or unzips between the nitrogen bases. –Then, the new nitrogen bases pair-up and attach to each half of the ladder. Results in two new DNA strands that are exact copies of the original DNA Molecules

The Role of DNA A single DNA molecule can have thousands of steps or base pairs. Arrangement of these steps form a genetic “code”. –This code determines the kind of gene that forms. –Different genes determine the different traits of an organism.

Genes: are sections of DNA on a chromosome that directs the making if specific protein. –Proteins is what determine our traits or characteristics Proteins are made out of amino acids, which are coded in DNA

Decoding the message First step in decoding the genetic message is to copy part of the nucleotide sequence from DNA to RNA –RNA codes information to a make proteins

RNA Ribose Nucleic Acid, is different from DNA –Different sugar –only has one strand –Has all the same bases but instead of Thymine, it has Uracil

Three types of RNA 1.m-RNA or messenger RNA that decodes the DNA into RNA and takes it out of the nucleus to a ribosome in order to make proteins.

2. r-RNA or Ribosomal RNA makes the Ribosomes where proteins are made 3. t-RNA or transfer RNA transports amino acid to the ribosome in order to make proteins.

Protein Synthesis Protein Synthesis is the process that cells use to produce protein. - it involves 2 distinct phases Transcription – occurs in the nucleus involves the creation of mRNA Translation – occurs in the cytoplasm at a ribosome – the protein recipe is “read” and the correct protein is made

Proteins are chains of amino acids. amino acid + amino acid + amino acid = protein The order of amino acids determines protein shape Shape determines function DNA code consists of the order of amino acids for each protein which comes from genes

Transcription: makes a copy of the DNA into RNA This is necessary because: DNA cannot leave the nucleus!!! Proteins are made on ribosomes in the cytoplasm. mRNA provides the solution Requires RNA Polymerase

RNA Polymerase During transcription RNA polymerase binds to the DNA strands and uses one strand as a template to assemble a strand of mRNA.

mRNA carries the code from DNA to the ribosomes

The Process of Transcription

Genetic Code Proteins are made from long chains of amino acids known as polypeptides.  Each polypeptide contains a combination of any or all the of the 20 different amino acids  “language” of mRNA comes from the “Genetic Code”  It is read in three letter nucleotide combinations known as a codon, which codes for a specific amino acid

Mutations: is any permanent change in a gene or chromosome.