Ch 16 transcirption RNA, and translation note

DNA, RNA, replication, translation, and transcription

Overview

Recall the central dogma of biology:

DNA (genetic information in genes) ! RNA (copies of genes) ! proteins (functional molecules) DNA structure

One monomer unit = deoxyribonucleic acid

•composed of a base, a sugar (deoxy ribose), and a phosphate

•directionality along the backbone ! 5’ (phosphate) to 3’ (OH)

Double-strand pairing:

•complementary base-matching: A-T, C-G

•base-matching achieved by H-bonding and geometry (long vs short nucleotides)

•antiparallel (one strand 5’!3’, the other 3’!5’)

Helical shape

•10.4 nucleotides per turn

•diameter = 2 nm

•both major and minor grooves

•called B-DNA. The helix twist and diameter can also change under dehydrating conditions and methylation to A-DNA and Z-DNA

Base-pairing and strand interactions

•A, G are long (double ring purines)

•C,T are short (single ring pyrimidines)

•need one long and one short nucleotide per pair

•C-G have three hydrogen bonds (slightly stronger matching)

•A-T have two hydrogen bonds (slightly weaker matching)

© M. S. Shell 2009 1/12last modified 10/27/2010

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