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DNA. Deoxyribonucleic acid. DNA is a nucleic acid. A nucleic acid is a polymer of nucleotides A nucleotide is made from a phosphate, sugar and base. www.chemsoc.org. Phosphate. From phosphoric acid http://bio.winona.edu/berg/ChemStructures/Phospha2.gif. Sugar.
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DNA Deoxyribonucleic acid
DNA is a nucleic acid • A nucleic acid is a polymer of nucleotides • A nucleotide is made from a phosphate, sugar and base. • www.chemsoc.org
Phosphate • From phosphoric acid • http://bio.winona.edu/berg/ChemStructures/Phospha2.gif
Sugar • Deoxyribose in DNA (Ribose in RNA) • http://www.mun.ca/biology/scarr/Deoxyribose_vs_Ribose.gif
Base • http://138.192.68.68/bio/Courses/biochem2/GeneIntro/GeneIntroResources/DNABases.gif
Purines • http://ghs.gresham.k12.or.us/science/ps/sci/ibbio/chem/notes/chpt14/purine.gif
Pyrimidines • http://ghs.gresham.k12.or.us/science/ps/sci/ibbio/chem/notes/chpt14/pyrimidine.gif
Nucleotide • Condensation between the phosphate and sugar (at C5) and between the sugar (at C1) and base • http://distancelearning.ksi.edu/demo/bio378/DNA_files/image002.gif
Dinucleotide • Two nucelotides join by condensation • http://pages.towson.edu/jdrawn/Chapter_1_Intro_to_Bioinfo_files/image005.jpg • Condensation gives phosphodiester bridge
Polynucleotide • Up to 5 x 106 nucleotides long • http://seqcore.brcf.med.umich.edu/doc/educ/dnapr/oligo.gif • 5’ end • 3’ end
DNA double helix • The bases of the DNA nucleic acid form H bonds to bases of a second molecule of DNA
A is the same amount as T • G is the same amount as C • Amount of purines equals the amount of pyrimidines • A always bonds to T • G always bonds to C
A bonds to T with two hydrogen bonds • G bonds to C with three hydrogen bonds. • http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/BasePairing.gif
The two nucleic acids wind into a double helix, with H bonds between polar groups of sugars keeping the shape of the helix. • (diagram from Bioligical Sciences, green, Stout & Taylor)
The two strands are ANTIPARALLEL • i.e. they are parallel, but run in opposite directions.
Arrangement of DNA in chromosomes http://www.biology.emory.edu/research/Lucchesi/multimedia/images/insert2.jpg
Histones in nucleosome • DNA is wrapped around a group of 8 histone proteins and held together by another histone molecule • http://employees.csbsju.edu/hjakubowski/classes/ch331/dna/nucleosome.gif
Nucleosomes: • Help in supercoiling of DNA • Help to regulate transcription
3’ end 5’ end Sugar-phosphatebackbone Base pair (joined byhydrogen bonding) Old strands Nucleotideabout to be added to a new strand 3’ end A 5’ end Newstrands 3’ end 3’ end 5’ end Figure 5.27 • The DNA double helix • Consists of two antiparallel nucleotide strands DNA Replication Animation http://www.johnkyrk.com/DNAreplication.html DNA Replication fork Adding Nucleotides