Chapter 10- Transcription and Translation Flashcards
Genetic Code Characteristics
Degenerate
Unambiguous
Non-overlapping, non-punctuated
Nearly Universal
Gene
Sequence of DNA that makes a functional product (Protein or RNA)
Common Promoter Element
TATA Box- Helps DNA polymerase bind
What percent of DNA encodes transcription factors?
8%
Cis Regulatory Elements
Enhancers
Insulators
Silencers
Enhancers
Facilitate RNA polymerase binding
Insulator
Sequence between enhancer and promoter that limits non-target gene transcription
Silencers
Repress gene expression by limiting RNA polymerase binding
Activators
Bind to enhancers
Repressors
Bind to silencers
Elongation
RNA polymerase reads template and adds bases in 5’ to 3’ direction
Termination
DNA sequence prompts RNA polymerase unbinding
Post-Transcription Processing Mechanisms
Spicling
5’ Capping
Poly-A Tail
Splicing
Exons connected while introns spliced out
Completed by spliceosome
Directed by consensus-RNA motif
Many mRNA can be made by single gene with alternative splicing
5’ capping
Methylated guanine added to 5’ end of mRNA to facilitate splicing and ribosome binding
Poly-A tail
100-250 adenines added to 3’ end of mRNA to increase stability
Genetic Basis of Prostate Cancer
Chromosome 8, region 8q24 mutation
MYC gene- proto-oncogene
Mutations in PVT1 (normal enhanced product) make enhancer interact with MYC gene to cause tumor growth
tRNA
75-80 bases that contain anticodon and amino acid binding region
Aminoacyl tRNA Synthetase
Catalyzed addition of amino acid to tRNA
One enzyme per amino acid
Translation initiation
Leader mRNA binds to small ribosome to line up start codon (AUG- methionine) to initiation complex
Translation Elongation
Large ribosome binds
tRNA binds to mRNA codons
rRNA ribozyme catalyzes peptide bond
Translation Termination
When ribosome reads stop codon, polypeptide is released and ribosome dissociates
Wobble Effect
3rd position of mRNA codon and 1st position of tRNA anticodon are non-specific
Charcot-Marie-Tooth Disease (CMT)
Defects in glycyl tRNA synthetase (GARS)
Glycine is unable to be added during translation
Dominant mutation
Progressive degeneration of distal neurons
Muscle weakness, atrophy, decreased motor skills
Post-translational modifications
Cleavage
Formation of quaternary structures
Signal sequences removed
Addition of chemical groups
Ubiquitin
Tag for misfolded or excess proteins to mark for degradation by proteasome
Prions
PrPc is normal brain protein
PrPsc is scrapie version, misfolded that accumulates and resists degradation
PrPsc contact with PrPc causes propagation of misfolding
Causes death of neuron and eventually organism
Prion diseases
Transmissible spongiform encephalopathies (TSEs)
Humans- Kuru
Muscle weakness, atrophy, loss of smooth muscle function, and death
