Biochem Lecture 14-15

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Biochem Lecture 14-15
2011-08-28 18:49:02
Biochemistry Hebert

Flash cards from medical school biochemistry
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  1. What are three diseases that involve DNA repair
    • Xeroderma pigmantosa --> Pyrimadine dimer problems
    • Ataxia telangiectosia --> ATM problems
    • HNPCC (Lynch Syndrome)
  2. What are the parts of Interphase?
    G1, S, and G2
  3. Name two Tumor Suppressor Genes
    p53 and RB
  4. Which phase involved the condensing of chromosomes?
  5. Which chromosomes are Acrocentric?
    13, 14, 15, 21, and 22 are the acrocentric chromosomes. These chromosomes give rise to ribosomal RNA
  6. When does crossing over occur?
    Prophase of meiosis I
  7. What is the consequence of nondisjunction?
    anueploidy – The chromosomes pair and don’t split
  8. How many copies of mtDNA are there per mitochondrion?
    between 2 and 10
  9. What does mtDNA code for?
    13 protein coding genes (for proteins involved with ATP synthesis), 2 genes for ribosomal RNA, and 22 tRNA genes
  10. Where did your mitochondria come from?
    all from mother, and do not follow Mendelian inheritance patterns
  11. Which has greater gene density, E. coli or Humans?
    E. Coli, by about 100X
  12. List the types of DNA and their prevalence
    repetitive (50%), heterochromatin (8%), regulatory (17%), Intronic (23.5%), Coding (1.5%)
  13. What allows for the start of the origin of replication
    DNaA, which melts the DNA at the origin of replication, allowing for polymerases to gain access
  14. What do the 3' and 5' mean?
    3' = hydroxyl group, 5' = phosphate group
  15. what stabalizes unwound ssDNA?
    ssDNABP (single strand DNA binding proteins)stick the the unwound strands
  16. What unwinds DNA?
    DNA Helicase
  17. What are the types of topoisomerases and what do they accomplish?
    • Type I DNA Topoisomerases- cut one DNA strand to relax supercoils then seal the nick
    • Type 2 DNA Topoisomerases- cut Both strands, allow the supercoil to relax, then seal the nick
  18. What are two drugs that target topoisomerases?
    • Etopside is an anticancer agent that targets human topoisomerase II
    • Quinolones target bacterial DNA gyrase, which is a type II topoisomerase
  19. What removes RNA primers in Prokaryotes and in Eukaryotes
    • Prokaryotes - DNA polymerase I
    • Eukaryotes - RNaseH and FEN1
  20. What are the key eukaryotic DNA polymerases?
    • Pol alpha - primase activity that adds a short piece of DNA to RNA primer
    • Pol delta - elongates strand and has 3' to 5' exonuclease activity
    • Pol epsilon - fills in the gap after the primer is removed
  21. What is a way to block DNA elongation?
    Nucleoside anologs with modified sugars are used for anti-cancer (cytarabine) or antiviral (zidovudine -AZT) treatment because they block DNA elongation.
  22. Four functions of telomeres
    • 1) Ensure that Genes are fully replicated
    • 2) Protect the end of chromosomes by having repetitive AGGGTT
    • 3) Shorten with Age (when gene replication is compromised, cell stops dividing
    • 4) Do not shorten in cancer cells or stem cells because these cells express telomerase
  23. What is telomerase
    • an enzyme comprised of protein and a short piece of RNA (thus a ribonucleotide)
    • has reverse transcriptase activity
    • maintains telomere length
    • expression of telomerase in primary cell lines results in their imortalization
  24. What are the 5 classes of histones?
    H2A, H2B, H3 and H4 form the nucleosome core, while H1 binds DNA between nucleosome beads (the linker histone)
  25. How do histones impact gene expression?
    the histones can be modified, (acetylated, methylated, and phosphorylated) especially on N-terminal tails which alters gene expression
  26. How is DNA packed into a chromosomal structure?
    It is first wound around histones, forming nucleosome beads, then packed more tightly into a 30nm fiber, and eventually into the final chromosomal structure
  27. which direction does DNA polymerase read the parental strand and synthesize new DNA?
    • Reads parental strand from 3' to 5'
    • synthesized new DNA from 5' to 3'
  28. What does DNA polymerase III accomplish?
    • catalyzes chain elongation (5' to 3' polymerase activity)
    • proofreading (3' to 5' exonuclease activity)
  29. What does DNA polymerase I do?
    • looks for nick between 3' end of new DNA and 5' end of RNA primer
    • Removes RNA primer (5' to 3' exonuclease)
    • fills in gaps accurately (5' to 3' polymerase, 3' to 5' exonuclease)