Presentation on theme: "Nucleotides Specification:"— Presentation transcript:
1 Nucleotides Specification: State that deoxyribonucleic acid (DNA) is a polynucleotide, usually double stranded, made up of nucleotides containing the bases adenine (A), thymine (T), cytosine (C) and guanine (G);State that ribonucleic acid (RNA) is a polynucleotide, usually single stranded, made up of nucleotides containing the bases adenine (A), uracil (U), cytosine (C) and guanine (G);
2 Polynucleotides Nucelic acids come in two forms: DNA and RNA They hold all the information to make proteins which is what all living things are made up ofAlmost all of the DNA in a eukaryotic cell is found in the nucleusRNA is found in 3 different forms
3 MonomersThe monomer of all nucleic acids (DNA and RNA) is called a nucleotideEach single nucleotide is made up of; one phosphate group, one sugar molecule, one organic nitrogenous baseAll three sub-units are joined by covalent bondsPBaseS
4 NucleotidesThere are five different nucleotides called A, T, C, G and UThe phosphate group in all nucleotides is the sameThe sugar molecule is a 5 carbon sugar; either deoxyribose in DNA or Ribose in RNAThe 5 possible bases are adenine; A, Thymine; T, Guanine; G, Cytosine; C, and Uracil; U
5 Joining nucleotides together A condensation reaction occurs between the phosphate group of one nucleotide and the sugar of another nucleotideRepeating the bonding gives a long chain of nucleotidesThis forms the ‘backbone’ of the molecule
7 Nucleotides to Nucleic Acids Chains of nucleic acids bond together to make nucleic acidsOnly nucleic acids carrying the same sugar (ribose or deoxyribose) can be binded togetherThis makes nucleic acids either RNA or DNA
8 Too Much Nucleic AcidUric acid is produced when excess purines (Adenine and Guanine) are broken down in the liverIt is excreted in urineSome people have too much uric acid in the blood which is turned into crystals that are deposited at the joints making them swollen (this is called gout)
9 TaskUsing Cambridge Biology p , outline the structure of DNA- you must include the key words in bold in the paragraphsWhen finished, complete the DNA modelling task titled ‘Have Your DNA and Eat It’Then complete the questions on the printed slide- they will be peer assessed next lesson!
10 Questions Outline how DNA replicates Define the term anti-parallel Write down the complimentary strand sequence for DNA and RNA- ATTAGGCTATIf a DNA is 20% Thymine, what percentage of each of the other types would it contain?What type of disease can result from DNA copying going wrong?
11 QuestionsOutline how DNA replicates semiconservatively- the double helix is untwisted, the hydrogen bonds between the bases are broken apart and ‘unzip’ to expose the bases, free DNA nucleotides are hydrogen bonded onto the exposed bases according to the base pairing rule A-T G-C, covalent bonds are formed between the phosphate of one nucleotide and the sugar of the next to seal the backboneDefine the term anti-parallel prallel, but with chains running in opposite directionsWrite down the complimentary strand sequence for DNA and RNA- ATTAGGCTAT DNA TAATCCGATA RNA UAAUCCGAUAIf a DNA is 20% Thymine, what percentage of each of the other types would it contain? 20% Adenine, 30% Cytosine, 30% GuanineWhat type of disease can result from DNA copying going wrong? Cancer may occur if DNA is not copied properly
13 DNA- Information Storage DNA is a long chain polymer of nucleotide monomersThe polymer is called a polynucleotideA DNA molecule forms when two polynucleotide molecules come together forming a ladder like structure
14 Hydrogen Bonding and Base Pairing The two DNA strands run parallel to each otherThe term anti-parallel is used because the strands run in opposite directions to one anotherThe chains are always the same distance apart because bases pair up in a specific way.When a purine appears on one side, a pyrimidine appears on the otherAdenine always pairs with thymine, and guanine always pairs with cytosineAs the strands come together, hydrogen bonds form between the basesThe base pairing is described as complimentary
15 Double HelixIn a complete DNA molecule, the anti-parallel chains twist, like twisting a rope ladder, to form the final structure known as a double helix
16 Making CopiesDNA replication takes place during interphase of the cell cycleIt is the process that creates identical sister chromatids
17 Making Copies In order to make a new copy of a DNA molecule: The double helix is untwistedHydrogen bonds between the bases are broken apart to ‘unzip’ the DNA and expose the basesFree DNA nucleotides are hydrogen bonded onto the exposed bases according to the base pairing rules (A-T and C-G)Covalent bonds are formed between the phosphate of one nucleotide and the sugar of the next to seal the backbone.
18 Making CopiesThis continues all the way along the molecule until two new DNA molecules (double helices) are formed, each is an exact replica of the original DNA molecule because of the base pairing rules.This process is known as semi-conservative replication.Each new DNA molecule consists of one conserved strand plus one newly built strand
19 How is the Structure of DNA related to its function? The sequence of bases acts as information storage in the form of codes to build proteinsThe molecules are long to store more informationThe base pairing means that complementary strands of information can be replicatedThe double helix gives the molecule stabilityHydrogen bonds allow for easy unzipping for copying and reading information
20 Reading the Instructions RNAContains the sugar riboseHas uracil instead of thymineUsually single strandedExists in 3 forms
21 Base Pairing of RNAContains the purines adenine and guanin and the pyrimidines cytosine and uracilBase pairing of A-U and G-C occur
22 Three forms of RNAmRNA: messenger RNA is made as a strand that is complimentary to one strand of the DNA molecule (the template strand) it is therefore a copy of the other DNA strand as it contains the opposite bases plus UracilrRNA: is ribosomal RNA and is found in ribosomes- it decodes mRNA into amino acidstRNA: transfer RNA carries amino acids to the ribosomes where they are bonded together to form polypeptidesTask: Now complete the Protein Synthesis sentence sort
24 Sentence Sort: What are the instructions for? The sequence of bases on DNA make up codes for particular proteins- they code for the sequence of amino acidsThe sequence coding for a particular protein (a gene) can be exposed by splitting the hydrogen bonds in the particular area of the DNA moleculeRNA nucleotides from a complementary strand (mRNA) which is a copy of the DNA coding strand (or gene)The mRNA peels away from the DNA and leaves the nucleus through a nuclear poreThe mRNA attaches to a ribosomeThe tRNA molecules bring amino acids to the ribosome in the correct order, according to the base sequence of the mRNAThe amino acids are joined by peptide bonds to give a protein with a specific primary structure which can then give rise to the secondary and tertiary shape of the protein
25 TaskComplete a windows movie explaining the steps involved in protein synthesisSuccess Criteria:No more than one minuteInclude scientific information and diagramsExplain simply the terms transcription and translation
26 QuestionsExplain why the MRNA strand produced in the nucleus is complementary to the template strand, and a copy of the coding strandIf a DNA template strand code reads ATTCGCGTTAAT, what would the complementary MRNA strand read?Suggest why MRNA is less stable than DNA, and explain why this is a necessary feature of MRNAMake a table to compare and contrast the structure of DNA with that of RNA
27 QuestionsExplain why the MRNA strand produced in the nucleus is complementary to the template strand, and a copy of the coding strand complementary RNA nucleotides are lined up against each base on the template strand, producing a complementary strand. As base pairing rules apply, this lining up will be the same as it appears on the coding strand- apart from U in RNA replacing T in DNAIf a DNA template strand code reads ATTCGCGTTAAT, what would the complementary MRNA strand read? UAAGCGCAAUUASuggest why MRNA is less stable than DNA, and explain why this is a necessary feature of MRNA RNA is single stranded and so less stable, as nucleotide bases are exposed and not paired. It also contains uracil instead of thymine, which may contribute to the lower stability of the molecule. mRNA results in the production of proteins. If the cell is to control protein production, the disintegration of mRNA stops too much of a certain protein being made, and so allows for regulation of the protein levels in a cellMake a table to compare and contrast the structure of DNA with that of RNA
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