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Cell Biology - Class 05
The in-depth study of human cells
By: David Botton

Nucleic Acids

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Nucleic Acids


(Nitrogen) Bases




Double Ring





Single Ring

Made from rings of Carbon and Nitrogen

Bases Pair through hydrogen bonds

A complementary with T (double bond)

G complementary with C (triple bond)

bases changed together through pentose sugar


with oxygen


with out oxygen

Base + a Sugar = Nucleoside

e.g. adenosine

throw in 3 phosphor = ATP (aka the universal high energy carrier)

as in cAMP

second messenger

eg. guaninosine

as in GTP

used in proten synthesis

carbohydrate metabolims

secondary messengers

eg. cytosinosine

as in CTP

Base + Sugar + Phosophor = Nucleotide

polynucleotides = multiple Nucleotides = DNA or RNA

phosphor can link to sugars to each other allowing for these nucleotide chains

Nucleotides are acids

AMP, TMP, UMP, GMP = RNA acid composition

dAMP, dTMP, dCMP, dGMP = DNA acid composition


Bases Used

A, G, U, C


differences between DNA and RNA

Double vs Single Stranded

T vs U

dR vs R sugar

chains of nucleoside 5' monophosphates

joined via 3'5' phosphodiester bonds

strands bound through hydrogen bonds to form the double helix are anti-parallel (5'->3' on side, 3' ->5' on other side)


Bases Used

A, G, T, C

Strands of DNA held together by hydrogen bonds between bases

Genetic information stored as sequence of basis along chain

DNA sequences only code how to make proteins

proteins are amino acids chained together

3 bases together code an amino acid

= codon

introns - that do not contain info

exons - contain info for an acid

64 total present in DNA (in any organism)

61 Amino acids

3 Stop codes

degenerate - several codes for same amino acid possible

a sequence of codons to produce a protein is a gene

gene expression - process of creating the protein

6.4 x 109 base pairs

20 - 30 thousand genes

DNA is folded into certain structures (p. 182)


DNA + Proteins (histones)

5 types of histones

H1, H2a, H2b, H3, H4

general mess of DNA when not organized in to chromosomes


core of 4 histones + DNA wrapped around this core


H1's used to create tighter packing together of nucleosomes

nucleofilaments are then coiled/twisted


chromatin sections organized in to recognizable arangements

46 total = 23 pairs

only present during cell division

DNA Replication

process of making copies of DNA

each strand is copied separately = semi-conservatively

ie. unzipped and each side copied

1. DNA aProtein

melts the DNA (splits the hydrogen bonds)

at origin of replication - start of copy alone

requires ATP

2. DNA Helicase

continues break/melt of DNA

requires ATP


Single Stranded Binding Proteins

Prevents DNA strands from reconnecting during replication

covers/binds to open strands

4. Primase (RNA Polymerase)

places section of RNA on to open strand

RNA primer needed before DNA can be made

5. DNA Polymerase III

Creates the complimentary strand of DNA, ie. performs the copy

DNA after primer

6. DNA Polymerase I

removes RNA primers and replaces it with DNA

(c) 2005 All Rights Reserved - David Botton