02 Central Dogma

02 Central Dogma - The Central Dogma and Protein Basics...

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The Central Dogma and Protein Basics HNFE 3025 Fall 2009
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Central Dogma Basic flow of genetic information Information is stored as DNA Flow: DNA mRNA Protein DNA is self-replicating DNA transcribed into RNA mRNA is translated into protein Proteins are the action molecules 2
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DNA Fig. 1-8, p. 8 Transcription / Translation
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DNA Information in DNA is based on the sequence of 4 bases Guanine ( G ), Adenine ( A ), Cytosine ( C ) , Thymine ( T ) Each base is part of a (deoxy)nucleotide – Purine or pyrimidine base + deoxyribose sugar + phosphate. Nucleotides are joined end to end 2 complementary strands are paired A T and G C Base sequences in one strand of DNA is copied (transcribed) into single-stranded RNA molecule RNA base (nucleotide) sequence based on sequence of G , A , C and U (Uricil) 4
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A Very Short DNA Molecule P OH S A T S P P S G C S P P S C G S P P S T A S P P S G C S HO P 5’ end 3’ end 3’ end 5’ end Sugar- phosphate backbone Hydrogen bonds between complementary bases The two chains are: •Antiparallel •Complementary A=T, G=C Held together by hydrogen bonding between complementary bases A deoxynucleotide 5
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Nuclear DNA The bases in DNA (and RNA) are covalently attached to the deoxyribose (ribose) sugars. If you know the base sequence of one strand of DNA, you automatically can determine sequence in the other strand – complementary bases The sugar-phosphate backbone carries a net negative charge due to phosphate groups. Each cell nucleus in our somatic cells(non-sex cells) contains 46 very long double-stranded (ds)DNA molecules. There is one dsDNA molecule per chromosome Before any cell divides by mitosis, chromosomes are duplicated; this means doubling the DNA by a process known as DNA replication. 6
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Nuclear DNA Is found associated with proteins in a complex known as chromatin DNA molecules are very long, so they are highly condensed to fit inside the nucleus The basic unit of DNA structure in the nucleus is the nucleosome A nucleosome has DNA wrapped around a core of histone proteins Histone proteins carry a net positive charge to help balance the net negative charge on the phosphates in the sugar-phosphate backbone of DNA Nucleosomes, are compacted together to form chromatin structures 7
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Nucleosome: basic unit of chromatin Histone core: 2 copies of each of histones H2A, H2B, H3 & H4 8
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9
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Transcription A section of a strand of DNA (template strand) is copied by transcription to make an RNA strand. The RNA strand will be complementary to the DNA strand that is transcribed The other DNA strand (sense strand) will have the same base sequence as the RNA with the exception of U in RNA and T in DNA 10
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Transcription is carefully regulated There are sequences of DNA usually upstream of the start site where proteins known as transcription factors can bind to increase or decrease transcription.
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This note was uploaded on 03/23/2010 for the course HNFE 3025 taught by Professor Mwhulver during the Spring '10 term at Virginia Tech.

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02 Central Dogma - The Central Dogma and Protein Basics...

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