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Introduction To Molecular Biology By Salwa Hassan Teama (M.D)
Molecular Biology • Molecular biology;thestudy of biology at the molecular level. • Molecular biology;thestudy of gene structure and functions at the molecular levelto understand the molecular basis of hereditary, genetic variation, and the expression patterns of genes. • The Molecular biologyfield overlaps with other areas, particularly genetics and biochemistry.
The genome of an organism is the totality of genetic information and is encoded in the DNA (or, for some viruses, RNA). The Genome commons.wikimedia.org/wiki/Image:Genome.jpg
Genome Database • The database is organized in six major organism groups: • Eukaryotes,Bacteria, Archaea, Viruses, Viroids andPlasmids.
Three Domain of Life All living things are grouped into three domain: • Eukaryotes; • Prokaryotes and • Archaea.
The cellis the smallest living unit, the basic structural and functional unit of all living things. Some organisms, such as most bacteria, are unicellular (consist of a single cell). Other organisms, such as humans, aremulticellular. The Cell
Cellsare stacked together to make up structures, tissues and organs. Most cells have got the same information and resources and the same basic material. Cells can take many shapes depending on their function. Function of cells Secretion (Produce enzymes). Store sugars or fat. Brain cells for memory and intelligence. Muscle cells to contract. Skin cell to perform a protective coating. Defense, such as white blood cells. The Cell
Eukaryotic Cell • Eukaryotesare generally more advanced than prokaryotes. There are many unicellular organisms which are eukaryotic, but all cells in multicellular organisms are eukaryotic. • Eukaryoticcells are found in animals; plants; fungi and protists cell.
Cell with a true nucleus, where the genetic material is surrounded by a membrane; Eukaryoticgenome is more complex than that of prokaryotes and distributed among multiple chromosomes; EukaryoticDNAis linear; EukaryoticDNAis complexed with proteins called "histones; Numerous membrane-bound organelles; Complex internal structure; Cell division by mitosis. Eukaryotic Cell
Unicellular organisms, found in all environments. These include bacteria and archaea. Without a nucleus; no nuclear membrane (genetic material dispersed throughout cytoplasm; No membrane-bound organelles; Cell contains only one circular DNA molecule contained in the cytoplasm; DNA is naked (no histone); Simple internal structure; and Cell division by simple binary fission. Prokaryotic Cell
Archaeaare prokaryotes; organisms without nucleus but some aspect of their molecular biology are more similar to those of eukaryotes. Archaea
Eukaryotic Cell Cycle :defined as the sequence of events that occurs during the lifetime of a cell and is traditionally divided into four phases: G1 = Growth and preparation of the chromosomes for replication S = Synthesis of DNA G2 = Preparation for mitosis M = Mitosis Eukaryotic Cell Cycle
Central Dogma of Molecular Biology • The flow of genetic information as follows: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPROTSYn.html
Deoxyribonucleic Acid (DNA),the genetic material of all cellular organisms and most viruses, the gigantic molecule which is used to encode genetic information for all life on Earth. Deoxyribonucleic Acid (DNA)
http://genome.gsc.riken.go.jp/hgmis/graphics/slides/01-0085jpg.htmlU.S. Department of Energy Human Genome Program, http://www.ornl.gov/hgmis.
Thread like structure. Located in the cell nucleus. The storage place for all genetic information. The number of chromosomes varies from one species to another. The Chromosome
In normal human cell DNA contained in the nucleus, arranged in 23 pairs of chromosomes ; 22 pairs of chromosomes (autosomes) ; the 23 chromosome pair determines the sex of individual and is composed of either two (x) chromosomes (female) or an (x) and (y) chromosome (male). The Chromosome
The basic units ofinheritance;itis a segment within a very long strand of DNA with specific instruction for the production of one specific protein. Genes located on chromosome on it's place or locus. The Gene
DNA andRNA are long chain polymers of small compound called nucleotides. Each nucleotide is composed of a base; sugar (ribose in RNA or deoxyribose in DNA) and a phosphate group. The phosphate joins the sugars in a DNA or RNA chain through their 5` and 3` hydroxyl group by phosphodiester bonds. General Structure of Nucleic Acid
The structure of DNA was described by British Scientists Watson and Crick as long double helix shaped with its sugar phosphate backbone on the outside and its bases on inside;the two strand of helix run in opposite direction and are anti-parallel to each other. The DNA double helix is stabilized by hydrogen bonds between the bases. • This structure explains how genes engage in replication, carrying information and acquiring mutation. • The G+Ccontent of a natural DNA can vary from 22-73% and this can have a strong effect on the physical properties of DNA, particularly its melting temperature.
There are four different types ofnucleotidesfound in DNA,differing only in thenitrogenous base: Ais for adenine; Gis for guanine;Cis for cytosine andTis for thymine. • These bases are classified based on their chemical structuresinto two groups:adenine and guanineare double ringed structuretermedpurine, thymine and cytosineare single ring structures termed pyrimidine. • The bases pair in a specific way: AdenineAwith thymineT (two hydrogen bonds)and guanineGwith cytosineC (three hydrogen bonds). • Within the structure of DNA, the number ofthymineis always equal to the number of adenine and the number ofcytosineis always equal toguanine. • In contrast to DNA; RNA is a single stranded, the pyrimidine base uracil (U) replaces thymine and ribose sugar replaces deoxyribose.
Eukaryotic genes:DNA molecules complexed with other proteins especially basic proteins called histones, to form a substance known aschromatin.A human cell contains about 2 meters of DNA.DNA in body could stretch to the sun and back almost 100 times. So it is tightly packed. Genomic DNA organization
Eukaryotic chromatinis folded in several ways. The first order of folding involves structures called nucleosomes, which have a core of histones, around which the DNAwinds ( four pairs of histones H2A, H2B,H3 and H4 in a wedge shaped disc, around it wrapped a stretch of 147 bp of DNA). Eukaryotic Chromatin
DNA Replication:The DNA (all gene) duplication; the transfer the genetic information from a parent to a daughter cell ; the DNAbase sequence are precisely copied. Replicationproceeds in a semiconservative manner, each strand of the DNA helix serves as a template for the synthesis of complementary DNA strands. This lead to the formation of two complete copies of the DNA molecule, each consisting of one strand derived from the parent DNA molecule and one newly synthesized complementary strand. DNA Replication
Mitochondria is a membrane-enclosed organelle found in most eukaryotic cells.These organelles range from 1–10 micrometers (μm) in size. Mitochondria generate most of the cell's supply of adenosinetriphosphate (ATP). Mitochondria are involved in a range of other processes, such as signaling,cellular differentiation,cell death, as well as the control of the cell cycle and cell growth. Mitochondria have been implicated in several human diseases, including mental disorders,cardiac dysfunction,[and may play a role in the aging process. Mitochondria has its own DNA. Mitochondrial DNA
Mitochondrial DNA • Mitochondrial DNA contains 37 genes, all of which are essential for normal mitochondrial function. Thirteen of these genes provide instructions for making enzymes involved in oxidative phosphorylation. • Oxidative phosphorylation is a process that uses oxygen and simple sugars to create adenosine triphosphate (ATP), the cell's main energy source. • The remaining genes provide instructions for making molecules called transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs). • Mitochondrial genesare among the estimated 20,000 to 25,000 total genes in the human genome.
Function of The DNA • Deoxyribonucleic Acid (DNA),the gigantic molecule which is used toencode genetic information for all life on Earth. • The chemical basis ofhereditaryand genetic variationare related to DNA. • DNAdirects the synthesis ofRNAwhich in turndirectsprotein synthesis.
The Genetic Code • The purine and pyrmidine bases of the DNA molecule are the letters or alphabet of the genetic code. All information contained in DNA represented by four letters: A,T,C,G. • Three nucleotides of DNA (1st, 2nd and 3rd) form triplet codons. A group of codons constitute the genetic code, that can be translated into amino acid of proteins. • RNA Codon tRNA Amino Acids
The sequence of codons in the mRNA defines the primary structure of the final protein. Since there are 64 possible codons, most amino acids have more than one possible codon. Out of the 64 possible 3-base codons, 61 specify amino acids; the other three are stop signals (UAG, UAA, or UGA). The Genetic Code
The RNA • Three major classes of RNA: messenger (mRNA), transfer (tRNA) and ribosomal (rRNA). Minor classes of RNA include small nuclear RNA ; small nucleolar RNA;………..
The concentration of purine and pyrimidine bases do not necessarily equal one another in RNA because RNA is single stranded. However, the single strand of RNA is capable of folding back on itself like a hairpin and acquiring double strand structure. The RNA
mRNAmolecules represent transcripts of structural genes that encode all the information necessary for the synthesis of a single type polypeptide of protein. mRNA; intermediate carrier of genetic information; deliver genetic information to the cytoplasm where protein synthesis take place. The mRNAalso contains regions that are not translated: in eukaryotes this includes the5' untranslated region, 3' untranslated region, 5' capand poly-A tail. Messenger RNA
All tRNAs share a common secondary structure represented by a coverleaf. They have four-paired stems defining three stem loops (the D loop, anticodon loop, and T loop) and the acceptor stem to which amino acids are added in the charging step. RNA molecules that carry amino acids to the growing polypeptide. Transfer RNA(tRNA)
Ribosomal RNA (rRNA) Ribosomal RNA (rRNA)is the central component of the ribosome, the function of the rRNA is to provide a mechanism for decoding mRNA into amino acids and to interact with the tRNAs during translation by providing peptidyl transferase activity.
Ribosomes ; Factory for protein synthesis; are composed of ribosomal RNA and ribosomal proteins (known as a Ribonucleoproteinor RNP). They translate messenger RNA (mRNA) to build polypeptide chains using amino acids delivered by transfer RNA (tRNA). Ribosomes
Ribosomes • Eukaryotic ribosomesare larger.They consist of two subunits; a 60S subunit holds (three rRNAs 5S,5.8S, 28S and about 40 proteins) and a 40S subunit contains (an18S rRNA and about 30 proteins) , which come together to form an 80S particle compared with prokaryotic 70S ribosome
Most mRNA are translated by more than one ribosome at a time; the result, a structure in which many ribosomes translate an mRNA in tandem, is called a polysomes. Polysomes
The Protein • Proteinsare the basic building materials of a cell, made by cell itself; the final product of most genes. • Proteinsare chain like polymers of a few or many thousands of amino acids. Amino acids are represented by codons, which are 3-nucleotide RNA sequences. Amino acids joined together by peptide bonds (polypeptide).Proteins can be composed of one or more polypeptide chains. • Proteins have many functions: provide structure that help cells integrity and shape (e.g. collagen in bone); serve as enzymes and hormones; bind and carry substance and control of activities of genes….
Four levels of a protein's structure: • Primary structure:Formed by joining the amino acid sequence into a polypeptide. • Secondary structure:Different conformation that can be taken by the polypeptide: alpha helix and strands of beta sheet. • Tertiary structure :Result from folding the secondary structure components of the polypeptide into three-dimensional configuration. • Quaternary structure :complex of several protein molecules or polypeptide chains, usually called protein subunits, which function as part of the larger assembly or protein complex.
Gene Expression • Gene expressionprocess by which a gene product (an RNA or polypeptide ) is made. • Intranscription steps,RNA polymerase make a copy of information in the gene (complementary RNA) (mRNA) complementary to one strands of DNA. • In translation step,ribosomes read a messenger RNA and make protein according to its instruction. Thus any change in gene sequence may lead to change in the protein product.
Transcriptional,prevent transcription, prevent mRNA from being synthesized. Posttranscriptional,control mRNA after it has been produced. Translational,prevent translation; involve protein factors needed for translation. Posttranslational,after the protein has been produced. Types of control in Eukaryotes
Mutation • Mutationincludeboth gross alteration of chromosome and more subtle alteration to specific gene sequence. • Gross chromosomal aberrations include: large deletions; addition and translocation (reciprocal and nonreciprocal). • Mutation in a gene's DNA sequence can alter the amino acid sequence of the protein encoded by the gene. Point mutations are the result of the substitution of a single base. Frame-shift mutations occur when the reading frame of the gene is shifted by addition or deletion of one or more bases.
Mutations can have harmful, beneficial, neutral, or uncertain effects on health and may be inherited asautosomal dominant, autosomal recessive,or X-linked traits.Mutations that cause serious disability early in life are usually rare because of their adverse effect on life expectancy and reproduction. Mutation
Common Tools in Molecular Biology • Nucleic acid fractionation • Polymerase chain reaction • Probes, Hybridization • Vector, Molecular cloning • Nucleic acid enzymes • Microarray • DNA sequencing • Electrophoretic separation of nucleic acid • Detection of genes: • *DNA: Southern blotting; inSitu hybridization; FISH Technique • *RNA: Northern blotting • *Protein: Western blotting, immunohistochemistry
Human Genome Project Goals • Identify all the approximately 20,000-25,000 genes in human DNA, • Determine the sequences of the 3 billion chemical base pairs that make up human DNA, store this information in databases, • Improve tools for data analysis, transfer related technologies to the private sector, and • Address the ethical, legal, and social issues (ELSI) that may arise from the project.
Molecular Biology : Uses • Various methods in molecular biology diagnose the different human diseases; diagnosis of an infectious agent, in malignancy, the presence of the genetic disease and in transplantation, paternity and forensic analysis. The Most Recent Applied Technologies • Genetic engineering • DNA finger-printing in the social and forensic science. • Pre and postnatal diagnosis of inherited diseases. • Gene therapy. • Drug Design.