Download Lesson02Background

Doug Raiford
Lesson 2
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Material of life
 Heritable traits
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The job of DNA is to produce
proteins
 Involved in virtually every
chemical reaction
▪ Enzymes catalyze reactions
 Structure
▪ muscle, cellulose, etc.
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Every cell has the same DNA
 Yet not all cells perform same
job
Background
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Double stranded
Sequence of nucleotides
 Named for their nitrogenous bases
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Adenine
Guanine
Cytosine
Thymine
Strands are complementary
 Gs with Cs, As with Ts
 Called base-pairs
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3
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Article: molecular structure
of nucleic
“It acids
has not escaped our notice
 Published
Nature
in April
of
thatinthe
specific
pairing
we have
1953
postulated immediately suggests
 http://www.nature.com/nature/dn
a possible copying mechanism
a50/watsoncrick.pdf
for the genetic material.”
 One page
 Possibly the most famous
passage in all of science
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Carbons
numbered
Synthesis
5’ to 3’
Strands are
antiparallel
Reverse
complement
Background
Deoxyribonucleic acid
5
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1
61
121
181
241
301
361
421
481
541
601
Can be represented as a string of characters
aataaatact
tcctatattt
ttagaagcaa
gcacctaaaa
gtacaattag
taccattatt
gactctgtag
tagagatcgc
atgctcaagc
aaatgttcca
taaattcgag
tacaggtatt
atcctcaata
ttcatctccc
ttaagtcgtt
ccataccatt
agcttctggg
agctggctca
gctctttaca
tgtaagcatc
gctcaattca
attcccagta
Background
ccacctgaaa
aaatatgcac
ttttaaaata
tctatgaaat
ccgacaatat
ttggcataag
atattcaaaa
cctattaaat
aatatctagg
aggtcgagat
gtctattggt
ctctttctat
aatagatctc
caaacttgca
ttattttagg
cgacatagga
ggaatacagg
gaataatgtc
acatcatcta
caagctcatt
agtacaccta
gactacatca
gaatgacttt
tactgagaaa
taggattgcc
tgtgaaatta
atattgagta
caaagactta
cctcgataca
aaacaactgc
gactaaaaca
ttaaattaat
atcgggcaac
caagtctata
actttatatt
ataaattaat
tatattaggt
gaacaagatg
aacctattcg
agcatcagaa
atattgttct
gtctctatcg
ttcataccta
accaccatgg
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DNA strand: chromosome
Genome: all chromosomes combined
Background
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Gene is a sub-region of DNA
As mentioned: job of a gene is to produce protein
 Each gene is associated with a particular protein
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Two step process
 Transcription
 Translation
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Central dogma
transcription
translation
DNA  RNA  Protein
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RNA polymerase
 Protein complex
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Free-floating nucleotides
stitches together
Result is single strand of RNA
 Messenger RNA
 mRNA
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Exact copy
Hence transcription
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Strand of amino acids
20 common aa’s
Folds into shape
Shape dictates function
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mRNA: 4 nucleotide alphabet
Protein: 20 amino acid alphabet
How translate?
 Triplet nucleotides “code” for amino acid
 Codon
atg  Methionine
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64 combinations of 3 nucleotides
But only 20 amino acids
Some amino acids are coded for by multiple
codons
CTA
CTC
CTG
CTT
TTA
TTG
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Leucine
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Ribosome
 Protein and RNA
complex
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AAs delivered by
Transfer RNA
(tRNA)
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Translation
DNA Replication
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Central dogma
transcription translation
DNA  RNA  Protein
RNA Polymerase
Ribosome
Free-floating nt’s
tRNAs
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Use the cell’s own machinery for replicating
DNA
Polymerase chain reaction (PCR)
 Free-floating nucleotides
 DNA Polymerase
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Amplifies a single or
small number of strands
into millions
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Instead of free floating
ATP, CTP, TTP, and GTP
 Small percentage is
dideoxy variant
 Stops transcription if
encounters one of these
 All fragments end with
A, C, T, or G depending
on test tube
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Dye-labeled chain terminators: can do all in
one chamber
Capillary electrophoresis instead of gel
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Sequence termination techniques
 Only 700-900 base-pairs at a time
 Very time consuming and labor intensive
Slow: human genome
would take 8,000 years
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Breakup into
random sized
fragments
Determine
sequences of
fragments
Reassemble
algorithmically
High-throughput
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Look for regions of overlap
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How the polymerase knows where to attach
The term expression: phenotypical expression
Now equated to protein production rate
RNA
polymerase
Promoter Region
Coding region
Start Codon
‘ATG’ = Methionine
Background
Terminator Region
Stop Codon: non coding
‘TAA’, ‘TAG’,
or ‘TGA’
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Background
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