Lecture 1 Introdution to Molecular Biology.pdf

September 2017 Molecular Biology Molecular biology: The branch of biology that deals with the...

September 2017 Molecular Biology Molecular biology: The branch of biology that deals with the formation, structure, and function of macromolecules MOLECULAR BIOLOGY essential to life, such as nucleic acids and proteins, Lecture 1 It is the field overlaps with other areas, particularly genetics and biochemistry. Eukaryotic Cell Prokaryotic Cell *Eukaryotic cells are found in animals, plants, and fungi Unicellular organisms such as Cell with a true nucleus, where the genetic material is bacteriaa nucleus (no nuclear membrane) and genetic material Without surrounded by a nuclear membrane dispersed throughout cytoplasm Eukaryotic genome is more complex than that of prokaryotes and distributed among multiple Cell contains only one circular DNA molecule contained in the chromosomes cytoplasm Eukaryotic DNA is linear and complexed with proteins DNA is naked (no nucleoprotein) called nucleoprotein such as histones Cell division by simple binary fission. Cell division by mitosis.  The Genome Is all the genetic material in the chromosomes of a specific organism. Encoded in the DNA (for some viruses, RNA). Only, 10% of all human genes have defined functions. Human Genome Human Genome Human Genome Arranged on multiple chromosomes (23 pairs of chromosomes) Twenty two pairs (autosomes). One pair (sex chromosome) (XX) (female) or (XY) (male). Humans have 23 pairs of chromosome in every somatic cell (except mature red blood cells), while germ cells (sperm and eggs) have half the normal number of chromosomes.  The Gene Gene: is a segment within a very long strand of DNA, or in some viruses RNA, which expresses to give protein. Genes are the basic units of heredity. Genes located on chromosome on its specific point called locus. Some chromosome rich in genes as (19-22), while some are poor (4-18) Allele is a gene that present in two locus of homologous chromosomes, if both alleles are identical (homozygous), but if both nonidentical (heterozygous) Each allele inherited from a different parent. Gene Structure Most of the genes consist of short coding sequences or exons are /interrupted by a longer noncoding sequence or introns. Also it contain the upstream sequence 20-30 bp for start codon AUG (methionine) where the RNA polymerase bind to the gene and some transcription factors called promoter. Some genes contain other site for binding of transcription factor and activating the transcription, located either upstream or downstream from gene called enhancer. Operator: is a region to which the repressor or inducer bind to.  Structure of Nucleic Acid DNA Nucleic acid either DNA or RNA is Deoxyribonucleic Acid long chain polymers of small chemical (DNA): is the genetic compound called nucleotides. material of all cellular Nucleotides are ring shaped compounds composed of: Itorganisms is responsible andformost preserving, viruses. copying and 1- Nitrogenous base: classified into: transmitting information a- Purine: double ringed structure (Adenine and within cells and from Guanine). generation to generation. b- Pyrimidine: single ring structures It is a double strand (a –helix) (cytosine, thymine and uracil). that twisted around each other, 2- Sugar and move in opposite direction 3- Phosphate group (antiparallel) and stabilized by hydrogen bonds. O C H-bonds stabilize a double helix N G HN C DNA is a polymer of H2N-C C CH N N 2’-deoxyribonucleotides 5’ end 5’ HO-CH2 NH2 O C 4’ 1’ N CH C 3’ 2’ C CH O O N H H N O H N H O P O CH2 O C C C C C G and C form 3 O O C CH3 N H N C-H C N C H-bonds HN T C G N C C N C CH N H O 2’-deoxyribose sugars O O N H Phosphodiester linkages O P O CH2 NH2 O H O C N N N H O CH3 Directional chain (5’ to 3’) N A H C C C C C CH C 4 Bases HC C A forms 2 H-bonds O C N H N C-H N N N with T purines: adenine & guanine N C C N T O P O CH2 A H O O pyrimidines: cytosine & thymine O 3’ 3’ end O-PO32  3.4 Å per bp minor major groove 34 Å (10 bp) per major turn minor groove groove Type of DNA sequences DNA sequences can be classified into: A) Nuclear DNA B) Mitochondrial DNA which classified into: Circular double strand DNA consist of 37 genes coding for protein responsible for 1- Gene: 2- Extragenic DNA: oxidative phosphorylation. transcriptionally transcriptionally active inactive  2- Extragenic DNA: classified into: a- Tandem repeat: b- Interspersed repeat: which consist of repetitive sequence repeat faraway from each other. beside each other which classified according to the number of nucleotide in repeated sequence into: 1- Satellite 2- Minisatellite 3- Microsatellite consist of large number short number of nucleotide in consist of 2-8 bp repeated of nucleotide in repeated sequences (10-60pb) and sequences. conserved repeated classified into: It is associated with sequences (100- hereditary disorders. 1000bp), which concentrated in a- Telomere b- hypervariable minisatellite centromere. present at end of chromosome for present around centromere and used in protection of them and maintain forensic and paternity test. its integrity. RNA Messenger RNA (mRNA) It is a transcripts of structural genes RNA (ribonucleic acid) is a single stranded. (DNA). Encode all the information necessary for the synthesis of a polypeptide of protein in cytoplasm. The pyrimidine thymine replaced by uracil (U) and ribose sugar replaces The first transcript called primary mRNA which contain both coding (exon) deoxyribose. and noncoding (intron) sequence. The primary mRNA undergoes three processes to give mature mRNA: There are three major classes of1-RNA: Messenger (mRNA) 1- Splicing: removal of noncoding sequence 2- Transfer (tRNA) 2- Capping: addition of 7 methyl-guanosine triphosphate to 5' terminus. 3- Ribosomal 3- Addition of poly (A) tail: involves cleavage of its 3' end and then the (rRNA). addition of about 200 adenine residues. Minor classes of RNA include small nuclear RNA  Transfer RNA/ tRNA It is a single strand RNA that carry correct amino acids to their position along the mRNA template to be added to the growing polypeptide chain. Ribosomal RNA/ rRNA Application of Molecular Biology It is the central component of the Research ribosome. Diagnosis Ribosome is the factory for protein synthesis, composed of ribosomal RNA and ribosomal proteins (known as a ribonucleoprotein or RNP). Transplantation rRNA provides a mechanism for decoding mRNA into amino acids. Paternity Forensic analysis Gene therapy Drug Design