INTRODUCTION TO MOLEULAR BIOLOGY

The first MICROBIOLOGIST and his MICROSCOPE

Anton van Leeuwenhoek - A classical example of serendipity. By wanting better magnifying lens with which to judge the quality of the cloth he was buying Leeuwenhoek discovered bacteria

1869

Friedrich Miescher isolates a substance, nuclein, from white blood cells on soiled bandages. Miescher, a scientist trying to characterize the biochemistry of cells, had identified the substance that would later be recognized to contain DNA.

1929

Phoebus Levene discovers that deoxyribose (a sugar molecule), a phosphate molecule, and four types of nucleic acid "bases" form the molecular building blocks of the structure of DNA. They are called nucleotides. At this time DNA is not recognized as the molecular structure of genes, but is recognized to exist in the nucleus of cells as part of the structure of chromosomes. Levene also recognizes that the fourtypes of nucleotides each contain exactly the same phosphate and sugar molecule, but have a different nucleic acid base.

1952

Maurice Wilkins and Rosalind Franklin obtain X-ray images of DNA crystals, revealing a regular repeating unit of molecular building blocks that correspond to the nucleotide components of DNA.

1952

Erwin Chargaff shows that DNA contains equal amounts of the nitrogenous bases adenine and thymine, and equal amounts of guanine and cytosine, the four nucleotide components of DNA

P PS- T=A- SP PS-G C-SP P S- A=T- SP PS-C G-S

1953

1953

James Watson and Francis Crick deduce the three-dimensional structure of DNA. Relying heavily on X-ray crystallography data and the work of Chargaff , Watson and Crick propose a three-dimensional molecular structure for DNA. Their model makes it possible to understand the function of genes (mutation, carrying hereditary information that directs the synthesis of proteins, and replication) at a molecular level, and makes a convincing argument that genetic information is carried by DNA, not protein.

Watson and Crick propose that the molecular structure of DNA representing genes consists of two strings of nucleotides connected across like a ladder. Each step contains either a G-C pair of letters or an A-T pair, accounting for Chargaff's observation that there is an A for every T and a G for every C in DNA. They also propose that this double-stranded ladder is twisted around itself into a “double helix” in a spiral staircase fashion. The particular sequence of nucleotide pairs up and down the double helix, they reason, constitute the genetic information and changes in the sequence represent mutation.

semi-conservative replication

They also propose that this structure immediately suggests a mechanism for replication: unzipping the two strands from end to end and replacing the missing letters in each pair with the complementary partner (e.g. A with T for one complementary pair, and G with C for the other). This mechanism, named "semi-conservative replication" creates two identical copies of the original molecule, with one strand completely conserved, and the other completely new.

1977

Frederick Sanger, Allan Maxam, and Walter Gilbert independently develop ways to sequence DNA. These methods allow, for the first time, the sequence of letters from fragments of DNA to be read biochemically. This allows scientists to read and translate the genetic information in DNA to determine the protein structure coded by a gene.

Dr Frederick Sanger, OM, CH, CBE, FRS (born 13 August 1918) is an English biochemist and a two times Nobel laureate in chemistry. He is the fourth person in the world to have been awarded two Nobel Prizes (first three were Marie Curie, Linus Pauling and John Bardeen), and the only person to receive both in chemistry.

1985

Kary Mullis invents the polymerase chain reaction (PCR), which amplifies select pieces of DNA. Up until this point, it is necessary to isolate large amounts of DNA from original sources to have enough to analyze biochemically.

Mullis, using adaptations of cellular mechanisms of semi-conservative replication, invents a method for replicating millions of copies of a DNA sequence from as little as a single original copy. This invention is the genetic equivalent of a printing press, allowing any trace amount of DNA to be amplified into enough copies for biochemical analysis and manipulation, this greatly facilitates research, medical testing, and forensic applications of molecular genetics.

MOLECULAR BIOLOGY

Molecular biology has represented a basic component of most basic research sciences that deal with the detection of minute quantities of nucleic acids to understand the molecular basis of heredity, genetic variation, and the expression patterns of genes.

MOLECULAR BIOLOGY

Different molecular techniques deal with molecular mechanisms and structures that are responsible for complex vital processes including cell growth and division, metabolism, differentiation and development.

MOLECULAR BIOLOGY

At the core of molecular biology is the evaluation of how nucleic acids and protein interact

at the molecular level

(DNA/DNA, DNA/RNA, DNA/Protein, and Protein/Protein interaction).

CENTRAL DOGMA OF MOLECULAR BIOLOGY

The central dogma of molecular biology defines that the flow genetic information is as follows:

CENTRAL DOGMA OF MOLECULAR BIOLOGY

DNA

TranscriptionRNA

Translation PROTEIN

TRANSCRIPTION

RNA Modification

Trimming: removing bases from the 5’ and 3’ ends

Capping: adding a methylated G to the 5’ end Necessary for RNA localization to the ribosome

Tailing: addition of A’s to the 3’ end of the mRNA More A’s = more stabile mRNA

Splicing: removing introns prior to mRNA transport to the nucleus

TRANSLATION

CENTRAL DOGMA OF MOLECULAR BIOLOGY

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPROTSYn.html

The genes function being expressed in the

form of protein molecules.

POLYMERASE CHAIN REACTION

Polymerase chain reaction is the most widely used techniques of molecular biology; PCR principle is a very simple practice by which a DNA or cDNA template is amplified many thousand or millions-fold quickly and reliably.

Life in the extremes

MOLECULAR BIOLOGY

Molecular biology allows the laboratory to be predictive in nature, it gives information that the patients may be at risk for disease (future).

Genetic engineering has enabled the cloning of many genes of, agricultural, industrial and medical importance, with the production of hormones and vaccines.

MOLECULAR BIOLOGY

The most recent applied technologies include:

-DNA finger-printing in the social and forensic science.

- Pre and postnatal diagnosis of inherited diseases. - Gene therapy. - Drug design.

Applications of PCR:

Diagnosis and screening of cancer and genetic diseases. Detection of microorganisms and viruses.e.g.

Mycobacteria and HCV, HBV, HIV. Detection of minimal residual diseases in leukaemia and

HLA typing.

Applications of PCR:

Amplification of archival and forensic material. Major role in the human genome project.Single point mutations can be detected by

modified PCR techniques such as PCR-single-strand conformational polymorphisms (PCR-SSCP) analysis.

Identify the level of expression of genes in extremely small samples of material, e.g. tissues or cells from the body by reverse transcription-PCR (RT-PCR).

RECOMBINANT DNA TECHNOLOGY

To analyze the structure, function, regulation and expression patteren of individual genes or families of genes has been facilitated by isolate genes from complex genomes and clone them into expression vectors

(recombinant DNA plasmids or bacteriophages) providing unlimited source of these DNA molecules for further procedure.

SUMMARY

In summary, molecular biology is facilitating research in many field including biochemistry, microbiology, immunology and genetics,…….

Future of Genomics