Molecular Biology Lecture 1 PDF

Molecular biology Introduction and brief history lecture1 Definition of molecular biology It is the science deals with macromolecules and to understand the five basic behaviors patterns(growth , division , specialization ,movement and interaction)in terms of the fine molecules responsible for t...

Molecular biology Introduction and brief history lecture1 Definition of molecular biology It is the science deals with macromolecules and to understand the five basic behaviors patterns(growth , division , specialization ,movement and interaction)in terms of the fine molecules responsible for them including (DNA ,RNA and Protein) Molecular Biology is the branch of biology that deals with the molecular basis of biological activity. It focuses on the interactions between various systems of a cell, including the interrelationship of DNA, RNA, and protein synthesis and how these interactions are regulated Warren Weaver(1938):was the first biologist used the term molecular biology as new branch of science Basics of Molecular Biology Molecular biology involves understanding the molecular mechanisms by which genetic information encoded in DNA is able to result in the processes of life. This includes: Structure and function of nucleic acids (DNA and RNA) Protein synthesis Gene regulation Definition of molecular biology Brife historical development Freidrich Miescher (1869) : was a Swiss physician and biologist. He was the first researcher who isolate and identify nucleic acid. It was a phosphate-rich chemicals, which he called nuclein (now nucleic acids), from the nuclei of white blood cells without knowing it responsibility about inheritance. so he knew much of the nucleic acid chemistry but their function remained unknown till a century later. However, his discovery played an important part in the identification of nucleic acids as the carriers of inheritance  Frederick Griffith(1928): demonstrates a heritable“transforming principle” that transmits the ability of bacteriato cause pneumonia in mice. Griffith´s experiment to identify the genetic material(bacterial model) Griffith's experiment, reported in 1928-29 by Frederick Griffith(british scientist) was one of the first experiments suggesting that bacteria are capable of transferring genetic information through a process known as transformation but he didnt realized the nature of the genetic materials Griffith used two strains of pneumococcus (Streptococcus pneumoniae)which is gr+ bacteria infect mice – a type S (smooth) and type R (rough) strain. The S strain covers itself with a polysaccharide capsule that protects it from the host's immune system, resulting in the death of the host, while the R strain doesn't have that protective capsule and is defeated by the host's immune system. Griffith´s experiment to identify the genetic material(bacterial model)  Avery–MacLeod–McCarty It was reported in 1944 ( as first described by Griffith's experiment in 1928) by Oswald Avery, Colin MacLeod, and Maclyn McCarty, to proof that DNA is the substance that causes bacterial transformation The physical analysis revealed that the Incubation the extract with Trypsin (proteas) or RNase didn’t stop transformation process and only DNase cause complete inhibition to the process thus they realize that the genetic material is the DNA rather than RNA or the protein The final process called Transformation  Hershey–Chase experiments to prove that the DNA IS the genetic material using virus. (phage) model Alfred Hershey and Martha Chase (1952)confirming that DNA was the genetic material (first demonstrated in 1944) using T2 phage virus The phage consists of a protein shell(capsule) containing its genetic material(DNA). The phage infects a bacterium by attaching to its outer membrane by tail fiber then injecting its genetic material leaving its empty shell attached to the bacterium.  They depend on the differences between protein &DNA chemical structure (DNA contains :C, H,O,N and P while protein :C,H.O.N,S) In their first set of experiments, Hershey and Chase labeled the DNA of phages with radioactive Phosphorus- P32 (the element phosphorus is present in DNA but not present in any of the 20 amino acids from which proteins are made). They allowed the phages to infect E. coli, and through several elegant experiments were able to observe the transfer of P32 labeled phage DNA into the cytoplasm of the bacterium In their second set of experiments, they labeled the phages with radioactive Sulfur-35 (Sulfur is present in the amino acids cysteine and methionine, but not in DNA). Following infection of E. coli they then sheared the viral protein shells off of infected cells using a high-speed blender and separated the cells and viral coats by using a centrifuge. After separation, the radioactive S35 tracer was observed in the protein shells, but not in the infected bacteria, supporting the hypothesis that the genetic material which infects the bacteria was DNA and not protein. Another important findings in molecular biology science Rosalind franklin& Maurice Wilkins 1950 (using X-ray crystallographic equipment to determine the 3 dimensional structure of the DNA or protein, James Watson (USA) &Francis Crick (1953) discovered DNA molecule structure depending on franklin Wilkins X-ray model.they won the 1962 Nobel Prize in Medicine for their discovery of the structure of DNA. They determined that DNA was double- stranded and took the shape of a twisted ladder or double helix. They also proved that complementary bases paired up with each other in the double strand of DNA. Adenine always pairs with thymine and guanine always pairs with cytosine. This was one of the most significant scientific discoveries of the 20th century Francis Crick in 1958 established the theory of central dogma of molecular biology that is to say the genetic information follow from DNA→RNA→PROTEIN -= Central Dogma of Molecular Biology The Central Dogma of molecular biology explains the flow of genetic information within a biological system. It is often summarized as: DNA-> RNA-> Protein 2. DNA replication 3. Transcription (DNA to RNA) 4. Translation (RNA to Protein)  Frederick Sanger1977 (95years) :is a British biochemist who was twice awarded the Nobel Prize for Chemistry, the only person to have been so. In 1958 he was awarded a Nobel prize in chemistry "for his work on the structure of proteins, especially that of insulin". In 1980, Walter Gilbertand Sanger shared half of the chemistry prize "for their contributions concerning the determination of base sequences in nucleic acids". 1980 Maxam–Gilbert sequencing is a method of DNA sequencing developed by Allan Maxam and Walter Gilbert in 1976–1977. This method is based on nucleobase-specific partial chemical modification of DNA and subsequent cleavage of the DNA backbone at sites adjacent to the modified nucleotides. 1983 Kary Mullis American chemist start synthesis a desired DNA sequence and to copy it using polymerase chain reaction ( PCR),  Kary mullis receiving his Nobel price Frederick Sanger United Kingdom James Watson (USA) &Francis Crick (1953) Terms in molecular biology the genome of an organism is its complete set of DNA. All the genetic information in an organism is referred collectively as a “genome”. Genomes vary widely in size: the smallest known genome for a free-living organism such as Mycoplasma genitalium) contains about 600,000 DNA base pairs, while human and mouse genomes have some 3 billion. The cxzof the human genome are not all in one continuous strand of DNA. the human genome is divided into of DNA, called chromosomes. 23 separate pairs Chromosomes are structures within the cell nucleus that carries genes. A chromosome contains a continuous molecule of DNA which is wrapped around histones. Human has 22 pairs of autosomes and 1 pair of sex chromosome, hence make up to 23 pairs of chromosomes. A gene is a DNA sequence that encodes a protein or an RNA molecule. Each chromosome contains many genes, i.e. the basic physical and functional units of heredity. Each gene exist in the particular position of particular chromosome. In human genome, it is expected that there are 30,000 - 35,000 genes.