Download Lect.5 - Department of Engineering and Physics

Biomolecular Principles:
Nucleic Acids and DNA
Mohamed Bingabr, Ph.D.
Associate Professor
Department of Engineering and Physics
University of Central Oklahoma
Deoxyribonucleic acid (DNA)
DNA Contains all the instructions for producing
every molecule currently in the cell (protein).
Human DNA extended 9 cm
storage of genetic information.
Origin of most diseases
DNA Structure
Nucleotides
Nucleic Acids
DNA
Nucleotide
Provide a mechanism for storage of genetic information.
Adenine Base (A)
Thymine Base (T)
Cytosine Base (C)
Guanine Base (G)
Nucleotides Bonding (1)
The phosphate linked to carbon 5
is coupled to carbon 3 through the
hydroxyl (53’).
Nucleotides Bonding (2)
Hydrogen bonding between bases.
Deoxyribonucleic acid (DNA)
DNA Fingerprinting (1)
Technique: Restriction fragment length polymorphism
(RFLP)
1) Restriction enzymes cut the long DNA strands into
small fragments. Enzyme EcoRI cuts the DNA at
every site that contains the sequence GAATTC.
DNA Fingerprinting (2)
2) Sort the fragment according to size using gel
electrophoresis
3) Press the gel against filter paper to create a replica
of the gel.
4) Soak the filter paper in a solution of radioactive
DNA probe.
DNA Fingerprinting (3)
1) Radioactive DNA will hybridize with the DNA
samples.
2) Radioactive bands can be photographed with x-ray
film, making a picture of the DNA fingerprint.
Chromosomes
• DNA is folded and
packaged into
chromosomes to fit
inside the nucleus.
• DNA is packaged with
proteins called
histones to form a
material called
chromatin.
Chromosomes
• Human cell contain 46 chromosomes arranged in 23
pairs.
• The paired chromosomes are called homologous
chromosomes: one is inherited from each parent.
• Genes are located on chromosomes.
Transcription and Translation
How is the sequence of nucleotide bases in a gene
used to synthesize a protein?
DNA Replication Machinery (1)
• Direction of replication 5’ to 3’
• DNA Helicase: unwinds the double helix
• Single-Stranded DNA Binding: keep DNA from
winding
DNA Replication Machinery (2)
• DNA polymerase: synthesis the DNA strand
• DNA ligase: join the Okazaki fragments
• Topoisomerase: prevents the twisting of the
chromosome
Lack of one protein prevent polymerization
DNA Transcription of a Gene
Promoter codon
Termination codon
mRNA Translation: Protein
Synthesis
The organelles ribosomes is a machine that is composed of
proteins and package of nuclec acids called ribosomal RNAs
Genetic Code (1)
• Genetic Code: The sequence in which the A, C, G,
and T organic bases appear on a strand.
• Gene: determines the instruction for linking amino
acids to form protein.
• Every three bases is a code (triplet) for one amino
acid.
• GAA is the code for the amino acid Glutamate
• AUG is the start codon and the code for the amino
acid methionine
• 3 billion organic bases encode 30,000 human genes
Genetic Code (2)
Control of Gene Expression
• All human cells contain the same genetic information
• Cells express only a fraction of the genes
• Different types of cells express different genes
• Example: Only certain cells of the pancreas express
the gene for insulin.
How is gene expression controlled in individual cells?
Regulation of Gene expression (1)
1. DNA Level: Transcription factors can bind to the
promotor regions to enhance or inhibit transcription
(steroid hormone)
Regulation of Gene expression (2)
2. RNA Level: Transcription of unstable mRNA that
degraded
Regulation of Gene expression (3)
3. Protein Level: Protein can be inactivated until they
are needed.
Application of Gene Expression
• Block expression of specific gene to study its function.
• Gene Therapy: block gene from excessive production
of protein.
Recombinant DNA Technology
• Techniques to transfer genetic information from one
organism to another.
• Molecular cloning: making a copy of a gene
Cloning of DNA Using Bacteria
• Bacteria used to clone
foreign segments of
DNA
• Same enzyme used to
cut the plasmid and
the foreign DNA.
• Transformation by
mechanical or
chemical technique
• Transfection: Inserting
plasmid to animal cell.
• Transduction: Inserting
gene to animal cell by
viral method.
Applications of Recombinant DNA 1
Genetically modified organisms
-Golden rice: produce provitamin A
and iron
-More resistance to environmental
damage and viral infection.
Applications of Recombinant DNA 2
Animal Models of Human Diseases
Alter the DNA to produce similar human diseases
- to study the efficacy of potential therapeutics to
human disease.
- to study the function of
unknown gene or protein
Gene Therapy and Viral Vectors
Retrovirus are single-strand RNA viruses that infect
animal cells and use the host transcription and
translation machinery to produce viral proteins (HIV).
DNA Disorder
Currently about 4,000 genetic disorders are known,
with more being discovered.
InterGenetic Inc in Oklahoma: OncoVue Breast Cancer Risk Test
http://www.intergenetics.com/intergenetics/index.html
Disorder
Mutation
Chromosome
22q11.2 deletion syndrome
Angelman syndrome
Down syndrome
Hemophilia
Color blindness
D
DCP
C
P
P
22q
15
21
X
X
P - Point mutation, or any insertion/deletion entirely inside one gene
D - Deletion of a gene or genes
C - Whole chromosome extra, missing, or both - see chromosomal aberrations
T - Trinucleotide repeat disorders - gene is extended in length
Cellular Physiological Lifestyle
Animation of Inner Cell Life with Music:
http://www.studiodaily.com/main/searchlist/6850.html
Animation of Inner Cell Life with Explanation:
http://multimedia.mcb.harvard.edu/media.html
Homework (due March 3)
There are different type of genetic disease. Write a
paper (2 - 3 pages) about a disease that is due to one
defected gene.
The paper should talk about:
- Symptoms of the disease
-The defected gene and its function
-The protein produced by the gene.
- The cause of the defected gene (inherited or viral)
-Possible cure for the disease
-Other interesting things about the disease