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Plant Breeding
New characteristics : Better qualities / Higher quantities
Environmental effects : Variation
Genetic effects : More stable
Genetic improvement :
Hybridization / Selection
Genetic engineering
Plant Molecular Biology
Plant biology and Molecular biology
Recombinant DNA techniques
Plant gene analysis
Isolation / Identification / Characterization
Gene expression /Product analysis
Transformation
Chromosome
Chromosome :
Polynucleotide chain
Nucleosome = DNA + Protein
Heritable property
Eukaryote: coding sequence
non-coding sequence
Nucleotide
Basic units of nucleic acid :DNA / RNA
Nucleotide: base / phosphate
deoxyribose / ribose sugar
Purine : Adenine / Guanine
Pyrimidine : Cytosine / Thymine / Uracil
Bases
Nucleic acid
Sugar-phosphate backbone
5’ --> 3’ phosphodiester bond
Double helix / helix
Complementary bases
AT, AU (2 H bonds)
CG (3 H bonds)
DNA
Unbranched polymer (nanotech: branched?)
4 subunits (dNTPs: dATP, dCTP, dGTP and dTTP)
Genetic information
Other function
Energy carrier
Signaling molecule
Coenzyme
Gene structure
• Structural sequence : Genetic code
• Regulatory sequence : Gene expression control
(promoter, terminator, enhancer)
Prokaryotic gene
Polycistronic mRNA (found in most prokaryotes)
information / code for > 1 protein
uninterrupted stretch of DNA
no intron
copied without alteration
Prokaryotic gene
RNA polymerase
interact loosely with chromosome
slide along DNA chain
bind tightly at promoter
separate at terminator
Prokaryotic gene
Prokaryotic gene
Promoter
Consensus sequence centered at -35 and -10
Prokaryotic gene
Terminator
Specific sequence
Stop signal for RNA polymerase
A run of U residues downstream of
a self complementary hairpin /
stem-loop structure
Prokaryotic gene
Terminator
Eukaryotic gene
mostly
Monocistronic mRNA : code for single protein
Exon / Intron : DNA and primary transcript
RNA processing for mature transcript
5’ capping
RNA splicing
3’ polyadenylation
Eukaryotic gene
intron
RNA processing
stability
membrane transport
translation efficiency
Alternative splicing : > 1 protein
Genetic recombination during evolution
Central Dogma
Transfer of genetic information
Replication
Semiconservative
Local separation
Template reading
3’ --> 5’ direction
dNTPs substrates
DNA polymerase enzyme
RNA primer
Replication
Replication accuracy
Mistake less than 1/109 nct added
Errors result in mutation :
silent mutation
loss of mutation
improved / novel phenotypes
Transcription
At specific regions / From DNA to RNA
Transcription / Transcribe / Transcript
Changes in composition :
properties :
function :
Transcription
Types / Function of RNA
mRNA rRNA and tRNA
snRNA : splicing, telomere maintenance
RNA enzyme / ribozyme : catalytic activity
RNA genome : genetic material (ss / ds)
RNA gene : RNA as final product
Transcription
DNA template
(sense/antisense, +/- , template/coding)
RNA polymerase (I, II, III)
NTPs substrates
Transcription factor
Transcription activating protein
Transcription
Transcription
Active genes:
may be transcribed 1000X
in each cell generation
A transcript:
may be translated for thousands copies
Translation
From polynucleotide to polypeptide
Basic unit: amino acid
Compositions:
mRNA
ribosome
tRNA:amino acid
other proteins
mRNA as template
Genetic code / Codon triplet
64 possible codons
20 amino acids
61 + 3 stop codons (UAA UAG and UGA)
Degeneracy / Degenerate codons
several codons for 1 amino acid
except for Met and Tryp
tRNA as aa carrier
70-90 nt long
Amino acid attaches
to the 3’ CCA
Anticodon on tRNA with
complementary bases
to codon on mRNA
Ribosome
2 subunits
rRNA + 50 rProteins
tRNA-mRNA lineup
in correct order
ss - mRNA / t RNA
ls - peptide bond formation
Translation
Translation direction:
template reading 5’ --> 3’
Tl start signal:
purine-rich sequence
5’ cap
AUG as tl start site
Methionine as first amino acid
Genetic code
Template: mRNA
Amino acid carrier: tRNA
31 tRNA molecules (euka)
for 20 amino acids
several t RNA for 1 aa
Genetic code
31 tRNAs for 61 codons
Some tRNA - mRNA
complete matching
Some tRNA - mRNA
required only first 2 nt
3rd position: mismatch
*Wobble*
Genetic code
Universal codes :
conserved among organisms
with minor exception:
codon usage
preferred codons for some amino acid
due to available tRNA
Translation
Transcription-Translation