DNA THE MOLECULE OF LIFE WHO? • DNA WAS DISCOVERED IN 1869 BY FREDERICK MIESCHER, BUT FOR ALMOST 100 YEARS ITS STRUCTURE STAYED A MYSTERY. • JAMES WATSON AND FRANCIS CRICK IN 1953 DISCOVERED THE STRUCTURE OF DNA • THEY HAD HELP FROM MAURICE WILKINS AND ROSALIND FRANKLIN (X-RAY CRYSTALLOGRAPHERS) HELPED TO DETERMINE THE DOUBLE HELIX STRUCTURE DNA STANDS FOR: DEOXYRIBONUCLEIC ACID • CONTAINS ALL THE „INSTRUCTION” TO BUILT AN ORGANISM – DIFFERENT FOR EACH TYPE OF ORGANISM ON EARTH • CODED INFORMATION – BASICALLY ALL THE INSTRUCTION TO PUT AN ORGANISM TOGETHER AND MAKE IT WORK • WHAT IS IN YOUR DNA – THAT DETERMINES WHAT INHERITED CHARACTERISTIC YOU HAVE THERE ARE MORE THAN 2M DNA STRANDS IN A SINGLE HUMAN CELL. DNA ROLLS UP WITH THE HELP OF PROTEINS INTO A THICK STRAND. DNA COMBINED WITH PROTEINS IS CALLED CHROMATIN THE MOST PACKED FORM OF CHROMATIN IS CHROMOSOME BEFORE REPLICATION IT CONTAINS ONE DNA MOLECULE) HUMAN KARYOTYPE • KARYOTYPE IS A CHARACTERISTIC OF INDIVIDUALS OF THE SAME SPECIES • THE KARYOTYPE IS THE SET OF ALL CHROMOSOMES THAT ARE LOCATED IN THE CELL NUCLEUS OF EACH SOMATIC CELL THAT HAS THEM. • THE HUMAN KARYOTYPE IS CALLED A SET OF 46 CHROMOSOMES, IN WHICH ALL THE GENES OF A PERSON ARE ENCODED. • THE NORMAL HUMAN KARYOTYPE IS COMPOSED OF 22 PAIRS OF AUTOSOMES AND 1 PAIR OF SEX CHROMOSOMES, WHICH ARE DENOTED BY THE SYMBOLS X AND Y WHERE? LOCATED IN THE NUCLEUS (EUKARYOTES) OR NUCLEOID REGION (PROKARYOTES) SOME DNA IS FOUND IN MITOCHONDRIA AND CHLOROPLASTS TOO DNA IS FOUND IN THE NUCLEUS ANIMAL, PLANT CELLS IN REALLY LONG STRUCTURES CALLED CHROMOSOMES GENE • ONE DNA MOLECULE CONTAINS A VERY LARGE NUMBER OF DIFFERENT GENES (WHICH MAKE UP ONLY 2% OF THE TOTAL DNA, THE OTHER 98% BEING SECTIONS THAT DO NOT ENCODE ANY FEATURES) • GENE IS SMALL SECTION OF DNA FOUND ON A CHROMOSOME • EACH GENE TELLS THE CELLS TO MAKE A PARTICULAR SEQUENCE OF AMINO ACIDS, WHICH ARE PUT PUT TOGETHER TO MAKE SPECIFIC PROTEIN… DNA : • DETERMINES WHAT PROTEINS THE CELL PRODUCES E.G HAEMOGLOBIN, KERATIN • DETERMINES WHAT TYPE OF CELL IT IS EG. SKIN CELL, RED BLOOD CELL REPEATING SEGMENTS • DNA STRANDS ARE POLYMERS MADE UP OF REPEATING UNITS CALLED NUCLEOTIDES (MONOMER) • EACH OF THEM CONTAIN THREE PARTS • SUGAR (RIBOSE) • PHOSPHATE GROUP (PO4) • NITROGEN BASE • DOUBLE STRANDED – HELIX • SUGAR AND PHOSPHATE GROUPS IN NUCLEOTIDES FORM A „BACKBONE” TO THE DNA STRANDS. • CONNECTED BY NITROGEN BASES (ONE OF FOUR DIFFERENT) JOIN TO EACH SUGAR BY HYDROGEN BONDS • EACH BASE LINKS TO A BASE ON THE OPPOSITE STRAND IN THE HELIX NITROGEN BASES ADENINE THYMINE GUANINE CYTOSINE COMPLEMENTARY – PAIR UP A–T G–C • BASES T AND C HAVE A SINGLE-RING STRUCTURE AND ARE CLASSIFIED AS PYRIMIDINES . • BASES A AND G HAVE A DOUBLERING STRUCTURE AND ARE CLASSIFIED AS PURINES. DNA CAN REPLICATE! • DNA REPLICATION IS THE PROCESS BY WHICH A MOLECULE OF DNA IS DUPLICATED. • PROCESS THAT OCCURS DURING CELLULAR DIVISION WHERE TWO IDENTICAL MOLECULES OF DNA ARE CREATED FROM A SINGLE MOLECULE OF DNA • SINGLE MOLECULE CONTAINING TWO STRANDS OF DNA IN DOUBLE HELIX FORMATION IS SEPARATED, WHERE EACH STRAND SERVES AS A TEMPLATE FOR THE NEW DNA MOLECULES • THE RESULT OF REPLICATION ARE TWO IDENTICAL DNA MOLECULES. EACH CONTAINS ONE OLD STRAND AND ONE NEW STRAND.
