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

NucleotideProvide a mechanism for storage of genetic information.

Adenine Base (A)

Thymine Base (T)

Guanine Base (G)Cytosine Base (C)

Nucleotides Bonding (1)

The phosphate linked to carbon 5 is coupled to carbon 3 through the hydroxyl (53’).

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 TranslationHow 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 2Animal Models of Human DiseasesAlter 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 VectorsRetrovirus are single-strand RNA viruses that infect animal cells and use the host transcription and translation machinery to produce viral proteins (HIV).

DNA Disorder

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http://www.intergenetics.com/intergenetics/index.html

Disorder Mutation Chromosome22q11.2 deletion syndrome D 22qAngelman syndrome DCP 15Down syndrome C 21Hemophilia P XColor blindness P 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

Currently about 4,000 genetic disorders are known, with more being discovered.

Cellular Physiological LifestyleAnimation 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