
Watson & Crick

Beedle & Tatum

Processes:
 Transcription (DNA to mRNA)
 Translation (mRNA to protein)

Importance of location
 Eukaryotes
 Prokaryotes

Review

Types of RNA in Gene Expression
 mRNA (messenger)-provides code for protein
 tRNA (transfer)-carries amino acids
 rRNA (ribosomal)-directs translation
 Requires DNA-dependent RNA Polymerase
▪ Core enzyme + sigma factor = holoenzyme
 Three forms in Eukaryotic Nuclei
▪ RNA Pol I –Pre-rRNA
▪ RNA Pol II**--Pre-mRNA
▪ RNA pol III –Pre-tRNA

RNA recognizes region to be transcribed
 Promotor regions
▪ TATA box
▪ CAAT box

Complementary mRNA produced from DNA



Often zones with high GC levels
Loop and release of mRNA
Protection
 5’ capped with 7-methyl G
 3’ tail polyadenylation


Prokaryotic cells translate immediately into
protein
Eukaryotic cells process mRNA before
translation occurs
 Cutting out Introns
 Protecting transcript

Splicing occurs by sequence
 snRNA and snRNP (spliceosomes), and/or
ribozymes (self-splicing enzymes)
 Many different proteins can result from one
transcript

mRNA
 Transcript

tRNA
 Carrier for amino acids

Ribosomes
 Two sub-units of protein with three pieces of RNA

Codons- 3 nucleotide codes for amino acids
 20 amino acides
 64 codons
 3 stop codons (UGA, UAA, UAG)
 1 Start codon (AUG-methionine)

Each codon brings in a tRNA anti-codon that
contributes one amino acid to the protein




Small sub-unit of ribosome binds to mRNA
Methionine “start”
Large sub-unit of ribosome enters
Initiation factors involved

Connection
 Next tRNA enters
 1st tRNA “hands” amino acid to 2nd tRNA, then
leaves
 Ribosome slides to free the next space
 Continuation for length of protein
 Elongation factors involved

Stop Codon is reached
 RF’s bind to stop codon
 Protein is released
 Ribosomal units disassociate

Exploring factors influencing gene expression

Expression and repression of genes

Brooker, R. J. (2011). Concepts of Genetics + Connect Plus Access Card.
McGraw-Hill Science Engineering, New York, NY.

Brooker, R. J., (2012). Genetics: analysis and principles. 4th Ed. McGrawHill Higher Education, New York, NY.

King, M. D. (2013). The Medical Biochemistry Page. Retrieved from:
http://themedicalbiochemistrypage.org/home.html.

McClean, P. E. (2013). Transcription. Retrieved from:
http://www.ndsu.edu/pubweb/~mcclean/plsc731/transcript/transcript1.ht
m

Unknown (2013). Three types of RNA polymerase in eukaryotic nuclei.
Retrieved from: http://mcb.berkeley.edu/courses/mcb110/ZHOU/lec.57.euk_trxn_apparatus.pdf







Cap & Tail
http://classconnection.s3.amazonaws.com/681/flashcards/894681/jpg/co
ding1330783434942.jpg
RNA Elongation
http://limbiclab.files.wordpress.com/2012/12/limbic_lab_dna_transcripti
on_diagram1.png
RNA Initiation http://9e.devbio.com/images/ch05/0503fig1.gif
Processing
http://www.genomebc.ca/glossary/Alternative%20Splicing%20(colourful
)_Image.gif
Translation Initiation
http://kvhs.nbed.nb.ca/gallant/biology/translation_initiation.jpg
Translation Elongation
http://kvhs.nbed.nb.ca/gallant/biology/translation_elongation.jpg
Translation Termination
http://utminers.utep.edu/rwebb/assets/images/17.17_Termination_of_tra
nsla.jpg