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