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chapter 12 Hagar Farag sec.L53 202104799 - Coggle Diagram
chapter 12 Hagar Farag sec.L53 202104799
Gene expression
function at two levels :
molecular function
organism's trait
activities of proteins determine structure and function of cells
cellular activity determine characteristics
enzymes are one catagory
one gene ecodes RNA molecule
encode functional proteins
hormones
enzymes
encode structural proteins
cell wall
ribosomes
do not encode polypeptide
tRNAs
part of ribosomes
rRNAS
into amino acids
central dogma
transcription
translation
Transcription
DNA is transcribed into an RNA copy
this mRNA specifies the amino acid sequence of a polypeptide
3 stages :
termination
RNA polymerase reaches the terminator.
RNA transcript dissociate from DNA
elongation
RNA polymerase slides along the DNA in an open complex
RNA polymerase synthesizes mRNA
Thymine instead of Uracil in mRNA strand
initiation
the promotor functions as a recognition site for sigma factor
DIRECTION OF TRANSCRIPTION 5' to 3'
DNA TEMPLATE READS 3' to 5'
prokaryotes
mRNAs can be translated immediately
Eukaryotes
mRNAs require processing into mature mRNA before translation
addition of tail and cap
increases stability and lifespan in cytosol
splicing
tRNA , rRNA -> self splicing
Translation
from RNA language ( nucleic acids )
to protein language ( amino acids )
one/more codons - one amino acid
codon = 3 RNA nucleotides
start sodon = AUG
determine reading frame
stop codons = UAA,UAG,UGA
Eukaryotes
7-methylguanosine cap
one TRANSLATION factor : eRF
start codon : kozak's sequences
prokaryotes
ribosomal-binding site
2 TRANSLATIONAL factors : RF1,RF2
start codon: downstream from ribosomal-binding site
tRNA - ANTICODON,ATTACHMENT SITE
Eukaryotes
tRNA methionine
prokaryotes
tRNA formyl-methionine
not identical to coding strand
aminoacyl-tRNA synthase
catalyzes linking amino acids
results in reactions
determine appropriate tRNA
RNA - codon
identical to coding strand
input energy
3 stages
termination
stop codon
release factors
completed polypeptide sequence
ribosomal subunits release
elongation
codon/anticodon recognition
elongation factors
peptide bond is formed
pepridyl transfer reaction
movement of translocation
initiation
requires initiation factors
requires input of energy
Prokaryotes
ribosomal binding sequence
initiator tRNA
Eukaryotes
guanosine 5' cap
start codon variable
ribosomes
Eukaryotes
different kinds
prokaryotes
one kind
large subunit
BINDS TO SMALL SUBUNIT
small subunit
binds to mRNA
3 SITES
E site
A site
p site