07BIS1012013ReplicLect_7

Bis101001spring2013genesandgeneexpressionrlrodriguez

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Unformatted text preview: in a semiconservative fashion. The semiconservative constraints on replication require that DNA be replicated in a semisemidiscontinuous fashion. BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 6 Milestones of Modern Genetics ­ April 25, 2003 — 50th anniversary of the April discovery of DNA BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 7 DNA Composition (everything you need to know) 1. DNA consists of three components: q q q 1. 2. q 2. DNA Structure YouTube Video Deoxyriboses are linked by covalent by phosphodiester bonds between Deoxyriboses the 3’’OH of the sugar and the phosphate group on the 5’ carbon of the the OH adjacent deoxyribose. adjacent The nitrogenous bases are of two types: q 1. The pentose sugar, deoxyribose Phosphate Four nitrogenous bases (A, T, G and C) Purines are double ring structures (A and G). G (guanine) can be Purines distinguished from A (adenine) by the oxygen on the double ring distinguished Pyrimidines are single ring structures (T and C). C can be distinguished from Pyrimidines T by the NH2 on the single ring structure. by In RNA, U substitutes for T and ribose substitutes for dexoribose (ribose In has an OH at both the 3’ and 2’ positions and U lacks the methyl group has and found on T). found In double stranded DNA (or in a DNA/RNA hybrid), strands are In antiparallel — the two ends of the DNA molecule must have opposing antiparallel 5’ PO4 and 3’OH groups. BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 8 The Nitrogenous Bases (p. 228) BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 9 The Nitrogenous Bases (p. 228) DNA RNA BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 10 DNA composition is species specific Chargaff documented that base compositions varied among species. Based on his chemical analysis of many different DNAs, he proposed the Chargaff’s Rules which state that in all species: [ A ] = [ T ] and [ C ] = [ G ] and [ A ] + [ G ] = [ C ] + [ T ]. BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 11 Nucleotides: The Sugars O O - P O O H N O 5’ N N H 1’ 3’ 2’ O O H H N N N N H H C O 4’ 1’ 3’ 2’ OH O O O- O O N O 4’ P H P O 5’ H C - ON N H H P O H O Deoxyribose Ribose BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 12 Nucleotides: The Phosphates OOOOO- P OH O N C H N O O- N N P O O- H C P O O H O H O- N N O H O O O N O H H P P H N H H C H N N H O OH H O O N N P N N N H O H Deoxyadenosine Monophosphate...
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