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▪
? Transfer of genetic information    How

▪
Flow of genetic information in one direction
▪ DNA?RNA (Transcription)? (Translation)  Protein

▪
Nucleotide: sugar + phosphate + bases

▪
Bases: Adenine   thymine   guanine cytosine

▪
Nucleotide-Nucleotide? phosphodiester bond

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Monotner
-Arnino aci d
CH3
Nucleotide
Fatty acid
Alanine
OH
NH2
Polypeptide
' DNA strand
Fat e
Starch
Monosacchari de
CH20H
OH
OH
Cellular Structure
Intermediate filarnent
Adipose cells fat droplets
Starch grains in a Chloroplast
Starch grains

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Cytop asm
Cell wall
Ribosomes
Nucleoid
Plasmid
0.5 pm
Cytoplasmic
membrarL

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▪
DNA Structure: DNA is a polymer of nucleotides

▪
Nucleotide: sugar + phosphate + nitrogenous bases

▪
Nucleotide-Nucleotide? phosphodiester bond
▪ DNA
1- double strand
2- doublhelix

3-  running from 5’ to 3’
4- supercoiled

5- carry the main genetic information in the 
    form of genes

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DNA
RNA
3'
AAA CAATTAGTCGTA G AA
AAA CAATTAGTCGTA GA A
REPLICATION
3' AAA CAA T TA G TC GTA GA A
TRANSCRIPTION OF
BOTTOM OF STRAND
TRANSLATION
Protein H2N- Phe
a
Asn
•s
eu -COOK

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▪ ⇒ Gene is a segment of DNA that specifies a protein 
▪     (via mRNA)
▪    E. coli contains about 4000 genes
▪   Genome: sum of all genes
▪   What are the differences between DNA and RNA?
▪  RNA: carry genetic information for protein synthesis, 
▪            from DNA in the form of codon

▪  - Codon: triplet bases    how many codon in bacteria

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▪
DNA is not arranged in one supercoil but in several

▪
supercoiled domains that are stabilized by special proteins

▪ Topoisomerase I? removes supercoils
▪ Topoisomerase II -?introduces supercoils
▪

▪ Plasmid
▪
Carry only unessential genes

▪ TYPES  OF PLASMIDS
▪
1- Resistance plasmids

▪
3- Plasmids encoding virulence factors

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▪ Major enzymes and proteins  involved in DNA replication
▪ ♦ Topoisomerase I: Removes supercoils

▪ ♦ Helicase: Unwinding of DNA double helix

DNA stablizing proteins: Prevent unwinding of double helix

▪ Primase:  responsible for the formation of primer
▪ ♦
▪  DNA polymerase III: Catalyze the addition of nucleotides  
▪  
▪ DNA polymerase I: Catalyze the hydrlysis of primer
▪  (RNA units) and replaced by DNA unit
▪ DNA ligase : ligation of Okazaki fragments

▪ DNA methylase : methylation of weak points of DNA strand

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▪ RNA = RiboNucleic Acid
▪ Sugar is ribose
single strand
bases: AU    GC

▪ What are the main differences between DNA and RNA

▪ Three major types of RNA are known
▪ mRNA = messenger RNA 
▪               carry the genetic information from DNA in the form
▪                of codons
▪ tRNA = transfer RNA
▪             transfer amino acid to ribosome in protein synthesis
rRNA = ribosomal RNA
▪               it is a structural components of ribosome

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RNA polymerase
(core enzyme)
Promoter
region
Sigma factor
Gene(s) to be transcribed
(light green strand)
31

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▪ Codon-? triplet bases   AUG  GGC    CUA
▪ AUG -> methionine        GGC  for glycine
▪ Number of codon  64            20 amino acids

▪ Codon degeneracy
▪ Most of amino acids are signaled by more than codon
▪ Leucin -? has 6 codons       alanine   has 4 codon

▪ Genetic code
▪ Set of amino acids with the  corresponding codons 
▪ Translation
▪ Process which nitrogenous bases sequences of mRNA

determine the amino acid sequence of protein

BACTERIAL GENETICS oct Lect 6.ppt

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