Protein synthesis

http://cellbio.utmb.edu/cellbio/ribosome.htm

DNA vs RNA

http://faculty.uca.edu/

~johnc/mbi1440.htm

http://www.algosobre.com.br/biologia/dna-e-rna.html

Types of RNAMessenger RNA (mRNA): copy of DNA

http://www.ncbi.nlm.nih.gov/Class/MLACourse/Modules/MolBioReview/transcription.html

Types of RNA Transfer RNA (tRNA):

Types of RNA

http://www.molecularassembler.com/KSRM/ListFigures.htm

http://www.chm.bris.ac.uk/motm/linezolid/linezolid.htm

http://www.langara.bc.ca/biology/mario/Biol2315notes/biol2315chap11.html

Genetic code

20 a.a. But only 4 RNA bases… If 2 nucleotides, only 16 a.a. (42 = 16) 3 nucleotides is great 43 = 64

http://www.cbs.dtu.dk/staff/dave/roanoke/genetics980320f.htm

Exercices together

Transcribe this DNA into mRNA: ACGGTATTACCGCTA UGCCAUAAUGGCGAU (Answer) Now translate this mRNA into a protein: AUGCAUUGUAUGGGUUAAGCG Met, His, Cys, Met, Gly (stop)

Transcription

Initiation: 1) RNA polymerase binds to DNA at a

promoter region 2) DNA unwounded and template strand

exposed

Transcription

Elongation: 1) mRNA synthesized in 5’ to 3’ using

template strand 2) elongation continues and DNA

already transcribed rewinds into double-helix

Transcription

Termination: RNA synthesis stops; mRNA and RNA

polymerase are released

http://www.dadamo.com/wiki/wiki.pl/Transcription_(DNA_transcription)

Check your understanding

Biology12 Textbook P. 241 # 1, 3-6, 8-11, 13 and 14

Posttranscriptional modifications

In eucaryotic cells 5’ cap is added to the start. It’s a 7-

methyl guanosine which protects the mRNA from digestion by nucleases and phospohotases. See p. 244 fig. 3

Poly-A tail is added by poly-A polymerase to the 3’end. It’s to protect and helps initiate translation.

Posttranscriptional modifications Introns are removed by spliceosomes.

http://faculty.uca.edu/~johnc/rnaprot1440.htm

Check your understanding

Biology12 Textbook P.249 # 1-5, 7-12

Translation: Initiation

Translation: Elongation

About

60 ms/peptide bond!

Translation: Termination

Animation of the whole protein synthesis: http://207.207.4.198/pub/flash/26/transmenu_s.swf

Check your understanding

Bio 12 p.254 # 1-4, 6, 7 and 9 Do Activity 5.4.1 p.269-270

Point mutation : Substitution of one base

Point Mutation :

missense and nonsense Silent

mutation:

Point mutation: insertion and deletion mutation

Check your understanding

Bio 12 p. 263 # 1, 6-8

Control Mechanisms

42 000 genes in humans! Housekeeping genes : always needed

in a cell Transcription factors turn genes on

when required

4 levels of control of gene expression Transcriptional: controls which genes

are transcribed or rate of transcription Posttranscriptional: controls

posttranscription Translational: controls how often and

how fast translation happens Posttranslational: Controls passage

through membrane and rate of activation of proteins and time its remains functional.

Operon control

Operon: cluster of genes under the control of one promoter and one operator in prokaryotic cells

Operator: regulatory sequences of DNA to which a repressor protein binds

The lac operon

http://fig.cox.miami.edu/~cmallery/150/gene/operon.htm

The trp operon

http://fig.cox.miami.edu/~cmallery/150/gene/feedback.htm

Check your understanding

Bio12 p. 258 # 1 – 6.