11.2 notes dna structure. what is dna? deoxyribonucleic acid = dna deoxyribonucleic acid = dna...

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11.2 Notes 11.2 Notes DNA STRUCTURE DNA STRUCTURE

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  • 11.2 NotesDNA STRUCTURE

  • What is DNA?Deoxyribonucleic acid = DNAHeritable genetic informationInformation passed down to you from parentsGenome: the complete set of genetic material from your parentsHuman Genome Project: Scientists tackling the challenge of sequencing the entire human genome (2000)

  • NucleotidesNucleotides ARE the building blocks (monomers) of nucleic acids (polymers).DNA IS a kind of nucleic acidEach nucleotide is made up of:A ring-shaped sugar called deoxyriboseA phosphate group A nitrogenous base (a single or double ring of carbon and nitrogen atoms)

  • There are FOUR types of nucleotides found in DNAThey only differ by their nitrogenous bases or ring structure.Thymine (T) single ring=PyrimadineCytosine (C) single ring=PyrimadineAdenine (A) double ring=PurineGuanine (G) double ring=Purine

    HINT: CUT PY (cut pie) = (Cytosine, Uracil, Thymine = PYrimidine!

  • How do the nucleotides pair?Cytosine and Guanine pair with 3 hydrogen bondsThymine and Adenine pair with 2 hydrogen bondsA=T and C=G

  • Quick QuizIf Guanine always pairs with Cytosine & Adenine always pairs with Thymine...then they are always found in set or equal amounts.If one strand of DNA has 20% Guanines, how many Cytosines?And Adenines? And Thymines?20%G + 20%C = 40% G&C ; that leaves 60%... 30% A and 30% T

  • Formation of the DNA strandEach nucleotide (A,T,G,C) is joined together by covalent bondsThe phosphate group on one nucleotide will join with the sugar group of another nucleotideNucleotides will be strung together by sugar-phosphate-sugar-phosphate forming what is known as a backbone.

  • The nitrogenous base pairs are lined up along the backbone.They meet in the middle of the Sugar-Phosphate backbone.Are like rungs on a ladder.

  • The Backbone and Base Pairs

  • A one ring structure pairs with a two ring structure.Must be a purine+ a pyrimidine Must have three rings TOTAL to make a rung of the DNA ladder

  • 1952: X-Ray EvidenceRosalind Franklin and Wilkins Using X-ray crystallography she was able to take a picture of DNAX shaped pattern = DNA twisted around itself like a tightly coiled springX shape pattern had to be a helix so DNA was an Alpha Helicase.

  • 1953: Watson & CrickThey were able to take all information from the work of scientists before themProposed a 3-D model of the DNA molecule capable of:copying itself accuratelybeing translated into a living organismIt was a double helix!

  • Complimentary Bases PairsTwo strands on the double helix. Run in opposite directions of each other. (youll see this in the activity today!!)The 2 strands are held together by base pairs that are complimentary to each other. A pairs with TG pairs with C.These combinations on both strings of DNA can be passed down from generation to generation on chromosomes.

  • Each cell of yours, whether blood cell or brain cell has 3 billion nucleotides, or 6 feet of DNA.DNA supercoils around histones (proteins) to form chromosomes remember where theyre located?? In the nucleus!How does all that DNA fit into one cell?