Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
DNA repair protein XRCC4 wikipedia , lookup
Homologous recombination wikipedia , lookup
Zinc finger nuclease wikipedia , lookup
DNA sequencing wikipedia , lookup
DNA profiling wikipedia , lookup
DNA replication wikipedia , lookup
Microsatellite wikipedia , lookup
DNA polymerase wikipedia , lookup
United Kingdom National DNA Database wikipedia , lookup
Nucleic acids Objectives • State that DNA is a polynucleotide usually double stranded, made up of nucleotides • State that RNA is a polynucleotide usually single stranded, made up of nucleotides Two types of nucleic acids • DNA (deoxyribonucleic acid) • RNA (ribonucleic acid) polymers • DNA and RNA are polynucleotides • They are made up of many monomers called nucleotides Nucleotide structure A phosphate group B sugar molecule (specify) C organic nitrogenous base (not just base) Nucleotides Phosphate Base Sugar A Nucleoside = sugar + base The sugar component • In DNA – Deoxyribose • In RNA – Ribose The phosphate component is always the same in DNA and RNA But there are 5 possible different organic nitrogenous bases The organic nitrogenous bases Purines Purines have 2 rings A adenine G guanine Pyrimidines C cytosine T thymine U uracil Formation of nucleotides Each component of a nucleotide is joined together by a covalent bond •Each polymer strand is a polynucleotide •Nucleotides are joined by phospho diester bonds to form a ‘sugarphosphate backbone’ •Chains of nucleotides joined together form nucleic acids •only nucleotides containing the same sugar can join together Homework • Find out how nucleotides may be involved in Gout • Interactive ICT DNA code activity on Finding the structure: pieces of the puzzle – Finding the structure only. This will be needed as background for the starter in the next lesson. THE DOUBLE HELIX Objectives • Describe how a DNA molecule is formed by H bonds between complementary base pairs forming 2 antiparallel DNA strands • Explain how DNA twists to form a double helix DNA is a double helix DNA is double stranded A DNA molecule forms when 2 polynucleotide chains bond together Q. What do you notice about the two polynucleotide strands? A. They run in opposite directions (antiparallel) Anti-parallel strands Base-pairing The two strands of DNA are held together by the base pairs. Q. What type of bond holds them together? A. Hydrogen bonds Q. Why do the bases always pair; A to T and C to G? A. Complementary shape, a pyrimidine will always pair with a purine Adenine and Thymine; Guanine and Cytosine have a ratio of 1 to 1. Answer…. • 24% is Adenine • Thymine must also be 24% • Total 48% Answer…. • 52% left for the other two bases • 26% each So how do they join? ‘A Tea for 2’ Adenine joins with Thymine by 2 hydrogen bonds …and the other base pair Cytosine joins with Guanine by 3 hydrogen bonds Which are weak or strong bonds? • What is the significance of the weak bonds?