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Describe the 7 steps of replication in order
- 1. Helicase finds origin of replication, then separates, and unwind the strands.
- 2. Topoisomerases cut unwound DNA relieving tension
- 3. Single Strand Binding Proteins maintain separation and protect single strand DNA
- 4. Primase makes RNA primer
- 5. DNA-Polymerase elongates chain using primer adding ducleotides to 3' end of new chain
- 6. DNA ligase joins Okasaki fragments
- 7. Telomerase adds telomeres
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fuction of DNA Polymerase
- Elongate chain adding nucleoties to 3' end only.
- Has exonuclease activity for proofreading/correcting errors in replication
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function of primase?
- Primase is an RNA-polymerase enzyme
- It lays the RNA primer that DNA-pol uses to elongate new chain.
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Function of Helicase
- Helicase is one of the most important enzymes because:
- It finds the origin of replication, then unwinds the ds-helix, and separates the strands
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functon of topoisomerases
cut the DNA to relieve tension due to unwinding
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function of single strand binding proteins
Maintain strand separation, and protec separated strands
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function of DNA ligase
DNA ligase joins segments of DNA together, ither Okasaki fragments, or after reparation
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function of nucleases
- enzymes that exise damaged or incorrect nucleotides for reparation.
- after nucleases exise bad nucleotides, DNA-pol must come in and fill the gap, and ligase then comes in and seals the job.
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function of telomerases
enzymes that add the telomere ends to chromosomes
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telomeres
nucleotide sequences in DNA, that dont code for anything, and shorted during replication, allowing some play for thing to shorten without cutting coding DNA
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What are Okasaki fragments?
- Fragments of new DNA, synthesized on lagging strand as replication fork opens.
- Later joined together by ligase
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nonsense codons
stop codon
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missense codon
code for different aminoacid
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conservative mutation
little change in structure and function of product protein
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is RNA single, or double stranded?
single stranded in ALL living forms, but ds in some known viruses
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is RNA monocystronic or polycystronic`
- monocystronic in Eukariotes (1 gene = 1 protein)
- polycystronic in Proks
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what's the promoter?
- sequence of codons that singnal the start of transcription
- includes TATA box, and Start Site
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How does transcription initiation complex form?
- 1. Transcription factors bind to TATA box at promoter
- 2. RNA-pol II binds to transcription initiation factors and unwinds DNA
- This is forms transcription initiation complex
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define each step in transcription
- 1. transcription initiation complex forms
- 2 RNA-pol II adds new nucleotides to 3' end of groing pre-mRNA chain
- 3. RNA polymerase transcibes a stop codon
- 4 Pre-mRNA gets modified
- 4.1 5' cap & poly(A) tail
- 4.2 splisosomes cut out introns and join exons
- 5 mRNA is exported to cytoplasm
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3 phases of translation
- 1. initiation
- 2. elongation
- 3. termination
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Energy expense of translation:
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