Structure & Function of DNA
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
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 DNAfrom twosources
1
2
3
4
Cut bothDNAs
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
DNAfragments
Othergenes
Gene V
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.