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Topic 7 Cont’d. Transcription and Translation. Transcription Basics. DNA vs. RNA. Transcription Basics cont’d. Directionality: read 3’-5’; made 5’-3’ Promoter & TATA boxes Nucleoside triphosphates Contains the sense strand and antisense strand

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Topic 7 Cont’d

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Topic 7 cont d

Topic 7 Cont’d

Transcription and Translation


Transcription basics

Transcription Basics

  • DNA vs. RNA


Transcription basics cont d

Transcription Basics cont’d

  • Directionality: read 3’-5’; made 5’-3’

  • Promoter & TATA boxes

  • Nucleoside triphosphates

  • Contains the sense strand and antisense strand

  • Sense strand = always 5’-3’ and is the same as the mRNA that is produced except T for U

  • Antisense strand = always 3’-5’ and is the strand that forms the template and is transcribed.


Animation sites

Animation sites

  • http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/transcription.swf

  • http://vcell.ndsu.nodak.edu/animations/transcription/first.htm


Translation

Translation

The process of polypeptide/protein production using mRNA as a guide

Requires:

mRNA transcript

tRNA

tRNA activating enzymes

ribosomes

genetic code…..


The genetic code

The Genetic COde


The genetic code cont d

The Genetic Code cont’d

  • It’s a triplet code (codon) = 3 bases code for 1 amino acid

  • There are 64 different codons

  • Duplication = degeneracy = possible for 2 or more codons to code for the same amino acid

  • Code is essential universal (find me 2 exceptions by next class for 1 point e.c. each)


Amino acids

Amino Acids


Topic 7 cont d

tRNA

  • All tRNAs have base-paired ds sections that become loops

  • Triplet bases complementary to mRNA codons…called anticodons

  • A 3’-5’ CCA terminal end for amino acid attachment

  • The above permit 3 distinct binding attachment of the tRNA to the ribosome


Trna cont d

tRNA cont’d


Trna a s f example

tRNA a S = F example

  • The base sequence of tRNa molecules vary = some variable features in its structure

  • An extra small loop is sometimes present

  • The bp sections are sometimes helical

  • Results in:

  • A distinctive 3-d shape

  • Distinctive chemical properties

  • ALLOWS THE CORRECT AA TO BE ATTACHED TO THE 3’ END BY A tRNA ACTIVATING ENZYME (aminoacyl-tRNA sythetase)

  • There are 20 different tRNA activating enzymes – one for each of the 20 diff. AA


Ribosome basics

Ribosome Basics

  • Composed of protein and rRNA

  • Consist of 2 subunits (small and large)

  • Possess 3 binding sites for tRNA (2 tRNAs can bind at the same time)

  • Possess a binding site for mRNA

  • Free vs. Bound (RER)

  • 80S in Euks vs. 70S in Proks & Euk. organelles


Ribosome 2 site version

Ribosome (2 site version)


Translation step 1 initiation

Translation Step 1 - Initiation


Polysomes movie time

Polysomes & Movie Time

  • http://vcell.ndsu.nodak.edu/animations/translation/movie.htm


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