snurps? describe how cells modify rna after transcription
TRANSCRIPT
Snurps?
describe how cells modify RNA after transcription
Promoter• DNA sequence where
RNA polymerase initiates transcription
describe how cells modify RNA after transcription
Trasnscription• Transcription factors +
RNA polymerase2=• Transcription initiation
complex
describe how cells modify RNA after transcription
Why is it called the TATA BOX?
describe how cells modify RNA after transcription
Termination• Transcription occurs until
Polymerase II reaches polyadenylation signal (AAUAAA)
describe how cells modify RNA after transcription
RNA processing• 5’Cap and poly-A-tail• Pre mRNA
describe how cells modify RNA after transcription
• Predict what needs to happen to this molecule.
• Average length of transcription is 27,000 base pairs. Average protein coded by 1,200 bp.
Splicing
describe how cells modify RNA after transcription
Introns• Cut out of the pre-
mRNA• Will be used later
describe how cells modify RNA after transcription
Exons• “exit nucleus” as
finished mRNA
describe how cells modify RNA after transcription
What do snRNPs do?
describe how cells modify RNA after transcription
snurps• Recognize splice sites• RNA and protein
molecules• snRNPs join with
eachother to build Spliceosomedescribe how cells modify RNA after transcription
What properties allow RNA to function as enzymes?
describe how cells modify RNA after transcription
What properties allow RNA to function as enzymes?
• Single stranded• Bases match up with each other• Some bases contain functional groups that
may participate in catalysis• Hydrogen bonding adds to specificty to its
catalytic abilitydescribe how cells modify RNA after transcription
Ribozymes• Introns become self
splicing ribozymes
What are Ribosomes?
Ribosomes• rRNA• Transcribed from DNA rRNA
• 3 molecules (bacteria)• 4 molecules (eukaryotes)• 2 sub Units
Describe how RNA is translated into proteins
• Psite- holds tRNA• Asite- holds next tRNA
holding next amino acid
• Esite- exiting tRNA
Describe how RNA is translated into proteins
Fig. 17-17
3355U
UA
ACGMet
GTP GDPInitiatortRNA
mRNA5 3Start codon
mRNA binding siteSmallribosomalsubunit
5
P site
Translation initiation complex
3
E A
Met
Largeribosomalsubunit
Video 1
Video 2
Fig. 17-18-1Amino endof polypeptide
mRNA
5
3E
Psite
Asite
Fig. 17-18-2Amino endof polypeptide
mRNA
5
3E
Psite
Asite
GTP
GDP
E
P A
Fig. 17-18-3Amino endof polypeptide
mRNA
5
3E
Psite
Asite
GTP
GDP
E
P A
E
P A
Fig. 17-18-4Amino endof polypeptide
mRNA
5
3E
Psite
Asite
GTP
GDP
E
P A
E
P A
GDPGTP
Ribosome ready fornext aminoacyl tRNA
E
P A
Predict which end of the mRNA moves through the ribosome first.
Describe how RNA is translated into proteins
Poly Ribosomes• Why?
Describe how RNA is translated into proteins
Where does polypeptide synthesis always begin?
Describe how RNA is translated into proteins
Where does polypeptide synthesis end?
• Option 1: cytosol• Option 2: Endoplasmic reticulum (marked by
signal peptide)
Describe how RNA is translated into proteins
• The ribosome recognizes these molecules at a complex called signal-recognizing particle (SRP)
Write your summary and Q’s