Prokaryotes vs Eukaryotes

But first it’s QUIZ TIME!! Copier is down – deal with it 1.Write the correct mRNA transcript based on the gene sequence below: GTA GTA GGT 2. Use your codon chart to determine the sequence of amino acids dictated by the gene sequence above.

mRNAAmino Acid AGA arginine GGA glycine AGC serine GCA alanine CAG glutamine 3. Which mRNA would code for both amino acid sequences shown, simply by a shift in the reading frame? …glutamine…glutamine…glutamine …serine… serine… serine A.AGUAGUAGUAGUC. GCUGCUGCUGCU B.AGCAGCAGCAGCD. GCAAGCGCAAGC

Use the amino acid chart from question #3 …glycine…serine…glycine… 4.Which of the following DNA strands would code for the amino acid sequence shown above? A.ACTCCTTCTC. CCGTCGACT B.TCTCCGTCGD. CCTTCGCCT

#5 and #6 5. An incoming tRNA would attach to which site on the ribosome? 6. If the tRNA anticodon is UUU, what amino acid will it bring to the growing peptide chain?

#7 and #8 7.Spliceosomes cut out ______ and splice together ________ which get expressed. 8. Modifications to the ends of the mRNA transcript are required before leaving the nucleus. Which end (3’ or 5’) is modified with a Poly- A tail?

II. RNA modification

5’ cap chemically speaknig

The movie – yes there is a movie naprocessing/movie.htmhttp://vcell.ndsu.nodak.edu/animations/mr naprocessing/movie.htm

Why Cap and Poly- A tail? Protect the messenger! exonucleases – protect but destroy

III Bacteria genetics Binary fission

Prokaryotic variation in genetic make-up Mutations Genetic recombination –Transformation –Transduction –Conjugation

Transformation

Transduction

Conjugation

IV. Control of metabolic pathways A.Two ways 1.Vary the activity of the enzymes (inhibit them or promote their ability) – feedback inhibition pathways 2.Vary the # of enzymes present – regulate enzyme production at the gene expression level

B. Gene regulation in bacteriaGene regulation in bacteria OPERONS! –Need to know that an operon is a section of DNA that contains genes for a protein –Need to know the parts and players

Ex 1 – Lac Operon

Ex 2 Tryptophan operon

A closer look at the parts A) promoter – site on DNA where RNA polymerase can bind and begin transcription B) operator – the “on/off” switch, located between promoter and structural genes C) structural genes – genes that code for a protein

Important players Repressor – a protein that when active will bind to the operator thus blocking transcription Regulatory gene – the DNA sequence that codes for the repressor protein Co-repressor – a molecule that attaches to an inactive repressor and makes it active Inducer – a molecule that attaches to an active repressor and makes it inactive

How they work together Negative regulation Positive regulation

Negative regulation Two examples –Lac operonLac operon –Tryptophan operon – best animation link everTryptophan operon