Structure & Function of DNA

DNA and RNA are nucleic acids that consist of long chains of nucleotides The nucleotides have three parts; 1.Phosphate 2.Nitrogen Sugar 3.base

DNA forms a double helix

In DNA there are four different nucleotides, each with a different nitrogen base. Adenine always binds with Thymine Guanine always binds with Cytosine This pattern is called complementary base pairing In RNA thymine is replaced by uracil

Complementary base pairing

The process of rewriting the instructions from a DNA molecule to an RNA molecule is called transcription Transcription is based on complementary base pairing

The process of assembling a protein from the instructions in messenger RNA is called translation

Translation is based on the Genetic Code, which is the same for all organisms

Three consecutive nucleotides (nitrogen bases) of a mRNA molecule are called a codon Each codon is the instructions to add one specific amino acid to the protein

The Genetic Code is the list of all possible codons and the amino acid each one codes for There are 20 amino acids and 64 codons

Sickle cell disease is caused by a mutation in only one nucleotide of the DNA

Sickle cell disease (sickle cell anemia) is caused by an abnormal type of hemoglobin called hemoglobin S. Hemoglobin is a protein inside red blood cells that carries oxygen. Hemoglobin S changes the shape of red blood cells, especially when the cells are exposed to low oxygen levels. The red blood cells become shaped like crescents or sickles.

The fragile, sickle-shaped cells deliver less oxygen to the body's tissues. They can also get stuck more easily in small blood vessels, and break into pieces that interrupt healthy blood flow. Sickle cell anemia is inherited from both parents. If you inherit the hemoglobin S gene from one parent and normal hemoglobin (A) from your other parent, you will have sickle cell trait. People with sickle cell trait do not have the symptoms of sickle cell anemia.

Genetic Transformation

Host Organism = Escherichia coli (E. coli) Bacteria contain one large chromosome and one or more small, circular pieces of DNA called plasmids that often contain genes for traits that increase the chance of survival. Bacteria can transfer plasmids back & forth in nature, and share these beneficial genes.

Figure 12.9 Isolate DNA from two sources Cut both DNAs Mix the DNAs and join them together 5 Clone the bacteria Bacteria take up recombinant plasmids 6 Find the clone with gene V 7 Grow bacteria and isolate protein V Bacterial cell Human cell Plasmid DNA DNA fragments Other genes Gene V Recombinant DNA plasmids Recombinant bacteria Bacterial clones Protein V

Genetic Transformation The jellyfish, Aequorea victoria, has a gene that produces a Green Fluorescent Protein or GFP that glows green. GFP has been inserted into a plasmid called pGLO. We will attempt to genetically transform the E. coli so that they will glow green.

pGLO Plasmid The pGLO plasmid contains; 1.Green Fluorescent Protein gene 2.Beta-lactamase gene Beta-lactamase is a protein secreted by bacteria that inactivates ampicillin 3.Previously contained genes that make digestive enzymes to breakdown the sugar arabinose

Genetic Transformation

Gene Regulation System The genes to produce these arabinose-digesting enzymes are only turned on when arabinose is present. When arabinose runs out or is absent the genes are turned off and do not make the enzymes. This is a Gene Regulation System

Gene Regulation System When the pGLO plasmid is produced, the gene for GFP replaces some of the genes for the arabinose-digesting enzymes. So, when arabinose is present the GFP gene is turned on and GFP is produced. When arabinose is absent the GFP gene is turned off and no GFP is produced.