TPR MCAT Biological Sciences: Molecular Biology

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  1. 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
  2. fuction of DNA Polymerase
    • Elongate chain adding nucleoties to 3' end only.
    • Has exonuclease activity for proofreading/correcting errors in replication
  3. function of primase?
    • Primase is an RNA-polymerase enzyme
    • It lays the RNA primer that DNA-pol uses to elongate new chain.
  4. 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
  5. functon of topoisomerases
    cut the DNA to relieve tension due to unwinding
  6. function of single strand binding proteins
    Maintain strand separation, and protec separated strands
  7. function of DNA ligase
    DNA ligase joins segments of DNA together, ither Okasaki fragments, or after reparation
  8. 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.
  9. function of telomerases
    enzymes that add the telomere ends to chromosomes
  10. 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
  11. What are Okasaki fragments?
    • Fragments of new DNA, synthesized on lagging strand as replication fork opens.
    • Later joined together by ligase
  12. nonsense codons
    stop codon
  13. missense codon
    code for different aminoacid
  14. conservative mutation
    little change in structure and function of product protein
  15. is RNA single, or double stranded?
    single stranded in ALL living forms, but ds in some known viruses
  16. is RNA monocystronic or polycystronic`
    • monocystronic in Eukariotes (1 gene = 1 protein)
    • polycystronic in Proks
  17. what's the promoter?
    • sequence of codons that singnal the start of transcription
    • includes TATA box, and Start Site
  18. 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
  19. 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
  20. 3 phases of translation
    • 1. initiation
    • 2. elongation
    • 3. termination
  21. Energy expense of translation:
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TPR MCAT Biological Sciences: Molecular Biology
some terminology, enzymes and processes from molec bio for MCAT
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