TRANSCRIPTIONTRANSCRIPTIONTRANSLATIONTRANSLATION

IB BIOLOGY IB BIOLOGY

TOPICS 4, 5TOPICS 4, 5

TRANSCRIPTION OVERVIEWTRANSCRIPTION OVERVIEW

1. 1. InitiationInitiation

RNA polymeraseIIRNA polymeraseII

TATA box TATA box

2.2. ElongationElongation

addition of RNA nucleotidesaddition of RNA nucleotides

5` 5` 3` direction 3` direction

3.3. TerminationTermination

AAUAAAAUAA

prokaryotes vs. eukaryotesprokaryotes vs. eukaryotes

Prokaryotic TranscriptionProkaryotic Transcription

Eukaryotic TranscriptionEukaryotic Transcription

4 types of RNA4 types of RNA

MESSENGER (mRNA) MESSENGER (mRNA) Single strandedSingle strandedTemplate for aa sequencing during Template for aa sequencing during

translationtranslationCodonCodon: 3 consecutive bases coding: 3 consecutive bases coding for a specific aafor a specific aa (64 possible codons for 20 aa)(64 possible codons for 20 aa)

Transfer (tRNA)Transfer (tRNA)

Sequence of Sequence of anticodonsanticodons

Link with aa and transfer them to Link with aa and transfer them to mRNA transcriptmRNA transcript

Ribosomal (rRNA)Ribosomal (rRNA)

building blocks of ribosomesbuilding blocks of ribosomes

Small nuclear RNA (snRNA)Small nuclear RNA (snRNA)

utilized in eukaryotic mRNA utilized in eukaryotic mRNA processingprocessing

TRANSLATION OVERVIEWTRANSLATION OVERVIEW

http://www.stolaf.edu/people/giannini/biological%20anamations.html

TranslationTranslation

The process of forming peptide bonds The process of forming peptide bonds between amino acids in a sequence defined between amino acids in a sequence defined by mRNA is called by mRNA is called translationtranslation. .

Involves:Involves: ((ii)  )  chargingcharging of the tRNA with the specific of the tRNA with the specific

amino acids andamino acids and ((iiii)  )  synthesissynthesis of of polypeptide chainpolypeptide chain by the by the

ribosomes. ribosomes.

tRNAtRNA

Anticodon Anticodon

      The middle loop that The middle loop that sticks out from the sticks out from the opposite end of the opposite end of the tRNA contains tRNA contains a triplet a triplet of bases of bases complementarycomplementary to the to the bases of the mRNA.  bases of the mRNA.  This triplet is referred This triplet is referred to as an to as an anticodonanticodon.  . 

Ribosomes page 63 Ribosomes page 63

Ribosomes are huge nucleic acid-protein Ribosomes are huge nucleic acid-protein complexes, each made of complexes, each made of two subunitstwo subunits (small and large) that come together only (small and large) that come together only during protein synthesis.  Otherwise they during protein synthesis.  Otherwise they float separately in the cytoplasm. float separately in the cytoplasm.

The Translation ProcessThe Translation Process

Translation consists of:Translation consists of:– initiationinitiation– elongationelongation– termination termination

Ribosome moves along the mRNA towards Ribosome moves along the mRNA towards the 3’ end. The start codon is nearer to the the 3’ end. The start codon is nearer to the 5’ end than the stop codon. 5’ end than the stop codon.

AnimationsAnimations

An overview of the subjectAn overview of the subject

Transcription and TranslationTranscription and Translation

Translation; the SequenceTranslation; the Sequence http://carbon.cudenver.edu/~bstith/http://carbon.cudenver.edu/~bstith/

transla.MOVtransla.MOV

Look over the gene expression in Look over the gene expression in eukaryotes page 61. eukaryotes page 61.

Regulation of transcriptionRegulation of transcription

AnimationsAnimations

Lac operon The lac OperonLac operon The lac Operon

Tryp operon Tutorial 13.2 The tryp OperonTryp operon Tutorial 13.2 The tryp Operon