Transcript Processing Protein Folding RNAi Gene Repair
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Transcription factor recognizes TATA Box and binds to DNA RNA
polymerase bonds to DNA RNA polymerase separates strands and
strings together complementary nucleotides (using U instead of T)
Primary transcript has been created when terminator region is
reached
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Transcription: Creates molecule to carry protein instructions
from DNA Creates exact replica complementary to DNA
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Alteration of ends of transcript: 5 end capped with modified
guanine Keeps RNA from degrading in the cytoplasm Cleavage factors
and stabilizing factors bind to 3 end Poly A polymerase binds and
cleaves 3 end and adds poly A tail made of adenine
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RNA splicing: Nucleotides removed Introns = non-coding regions
Exons = coding regions to be expressed Small nuclear
ribonucleoproteins (snRNPs) = proteins that detect adenine at
branching site Spliceosomes remove the intron and bind the two
exons
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The sequence of amino acids defines a proteins primary
structure.
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Blueprint for each amino acid is characterized by base triplets
Found in the coding region of genes Ribosomes recognize triplets
and create proteins
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Covalent bonds between amino acids help stabilize the protein
Shape and stability also maintained by chemical forces
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Chaperone proteins: Prevent nearby proteins from
inappropriately associating and interfering with proper folding
Surround protein in protective chamber during folding Ex) bacteria:
GroEL and GroES Use ATP Also assist in refolding proteins
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Chaperone proteins protecting folding proteins
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Models of protein folding: Diffusion Collision Model: Nucleus
is formed Secondary structures collide and pack together Nuclear
Condensation Model: Secondary and tertiary structures are made
simultaneously
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RNAi = RNA Interference RNAi is used to: Silence specific genes
Fix gene expression problems in mammals Also known as:
Cosuppression Post Transcriptional Gene Silencing Quelling
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Types of small silencing RNA: Small interfering RNA (siRNA)
Endogeneous: derived from cell Exogeneous: delivered by humans
Micro RNAs (miRNA) PIWI-interacting RNAs (piRNA) RNAi breaks up
mRNA before it is synthesized.
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Allows singling out of genes to determine function.
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Could halt progression of: Cancer HIV Arthritis All other
diseases
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DNA can be damaged by: Radiation (gamma, x-ray, and
ultraviolet) Oxygen radicals from cellular respiration
Environmental chemicals (hydrocarbons) Chemicals used in
chemotherapy
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Four major types of DNA damage: Deamination: amino acid group
lost Mismatched base Backbone break Covalent cross-linkage between
bases Deamination in DNA
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Repairing damaged bases: Direct chemical reversal Excision
repair mechanisms: Base excision repair (BER) Nucleotide excision
repair (NER) Mismatch repair (MMR)
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Chemical Reversal Ex) glycosylase enzymes remove mismatched T
and restore correct C
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Excision repair mechanisms: Base excision repair: DNA
glycosylases identify damaged bases DNA glycosylases remove damaged
bases Deoxyribose phosphate backbone component removed, creating
gap Gap filled with correct nucleotide Break in strand ligated
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Excision repair mechanisms: Nucleotide excision repair: Protein
factors identify damage DNA is unwound Faulty area is cut out and
the bases are removed DNA is synthesized to match that of the
opposite, correct strand DNA ligase adds synthesized DNA
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Excision repair mechanisms: Mismatch repair Corrects mismatches
of normal bases (A&T, C&G) by: Identifying mismatched bases
Cutting mismatched bases