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Students or teachers? LICEO SCIENTIFICO “GIUSEPPE NOVELLO” INDIRIZZO LINGUISTICO CLASSE 3^M DNA CHEMICAL COMPOSITION DNA is made up of Nucleotides, that are really important for living organisms, as they are the structural components or building blocks of DNA and RNA and they control all hereditary characteristics . DNA CHEMICAL COMPOSITION Each nucleotide contains a molecule of sugar,a phosphate group and an organic base. The sugar and the phosphate group are identical in each nucleotide, instead the organic bases are different. NUCLEOTIDE’S SUGAR The 5-carbon sugars ribose and deoxyribose are important components of nucleotides and are found in RNA and DNA. The sugars found in nucleic acids are pentose sugars and it has five carbon atoms. OH PHOSPHATE GROUP Nucleotides can have one, two, or three phosphate groups. Nucleotides with two or three phosphate groups are good energy donors. Phosphate groups can also be joined to other molecules, such as sugar. NITROGENOUS BASE Nucleotides in DNA contain four different nitrogenous bases: Thymine(T), Cytosine(C), Adenine(A) and Guanine(G). There are two groups of bases: Pyrimidines: Cytosine and Thymine that have a single six-member ring. Purines: Guanine and Adenine which have a double ring made up of a five-atom ring attached by one side to a six-atom ring. These bases are the part of DNA that stores information. DNA’S STRUCTURE DOUBLE HELIX Nucleotides are attached together to form two long strands that spiral to create a structure called a double helix. THE COMPLEMENTARY OF BASES The 'rungs' of the DNA ladder are each made of two bases, one base coming from each leg. The bases connect in the middle: 'A' only pairs with 'T', and 'C'only pairs with 'G'. The bases are held together by hydrogen bonds. DNA FUNCTIONS Bring information for the proteins Transmit genetic information BRING INFORMATION FOR THE PROTEINS The disposition of the 4 bases (adenine, thymine, guanine and cytosine) constitutes the genetic information, that can be read through the genetic code, which avoids the translation into amino acids. This process is possible just if there is a molecule of RNA. TRANSMIT GENETIC INFORMATION The genetic information is duplicated before the cell division, by way of DNA replication, that prevents the loss of information. The genetic information is trasmitted by the chromosomes. CHROMOSOMES • A chromosome is a packaged and organized structure containing most of the DNA of a living organism. • Each chromosomes is situated in a particularly part of the cell, called nucleus. The number of chromosomes varies from species to species: In the human body there are 46 chromosomes RNA’s functions Ribonucleic acid (RNA) is a molecule implicated in various biological roles in coding, decoding, regulation, and expression of genes. RNA’s structure In RNA, the sugar is ribose instead of deoxyribose. • In RNA, we can find uracil instead of thymine. • The RNA does not form a double helix but has the structure of a simple chain . • The three-dimensional structure of RNA is far more different than that of the DNA . • Fate clic per modificare il formato del testo della struttura Secondo livello struttura Terzo livello struttura Quarto livello struttura Quinto livello DNA EXTRACTION FROM A KIWI Ingredients: • Kiwi • Dishwashing liquid • Salt • Water • Ice • Cold alchool • Pineapple Fate clic per modificare il formato del testo della struttura Secondo livello struttura Terzo livello struttura Quarto livello struttura Quinto livello PROCESS 1 Put alchool in ice (the colder the ethanol is, the greater the amount of DNA that is percipitated) PROCESS 2 Prepare an extraction solution with -3g of salt -10ml of dishwashing liquid -90ml of water PROCESS 3 Shake slowly to dissolve salt, without making bubbles PROCESS 4 Peel the kiwi fruit and chop it into small chunks, mash them and put the pulp in a becker PROCESS 5 Put the becker into hot water (60°C) for 15 minutes PROCESS 6 After 15 minutes, you have to cool and to filter it by a special paper PROCESS 7 Gently, pour the cold alcohol along the wall of the tube, with the aim of forming a phase above the filtrate PROCESS 8 After a few minutes at the interface between the two phases it will form a gelatinous mass: the kiwi’s DNA Fate clic per modificare il formato del testo della struttura Secondo livello struttura Terzo livello struttura Quarto livello struttura Quinto livello WHAT HAPPENED? The cells are composed by robust cell walls, cell membranes and within the nucleus they contain DNA and a large number of proteins The high temperature destroys the cell walls exposing the cell membranes The dishwashing liquid dissolves cell membranes The salt condenses the DNA, however given that it is not soluble in alcohol, it appears as a gelatinous substance at the interface.