crassirostris
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Transcript crassirostris
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