Biology

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tay
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78449
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Biology
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2011-04-10 16:20:16
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pt 2
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  1. Why is DNA so important? What is it responsible for?
  2. Watson & Crick received the Nobel Prize for what amazing discovery?
    3-D model of DNA Double Helix.
  3. How many pairs of chromosomes do humans have? How many total chromosomes do humans have?
    • 23 pairs of chromosomes
    • 46 chromosomes.
  4. At the turn of the century, there was much debate regarding what was the molecule responsible for inheritance. What was the key factor in determining what the genetic material was?
  5. What was learned by Griffith’s experiments working with bacteria? Know the experiment and its importance. What is transformation?
    • Experiment: used mice, injected them with various strains of pathogens. mouse with R cells and the heat- killed S cells.
    • they learned that DNA carries necessary information for bacterial transformation.
    • transformation- tendency for bacteria to take foreign DNA and amke it a part of their own DNA.
  6. In 1944, Avery, McCarty & MacLeod made a major announcement. What was it and why was it so important?
    announced that the transforming substance was DNA.
  7. What is a bacteriophage and what is its importance in molecular genetics research?
    Bacteriaphage- is a virus that infects bacteria.
  8. How do viruses infect bacteria?
    attached to a baerterial cell and forces the virus genetic material inside the cell. later it replicates. use it as a host.
  9. Know the famous Hershey & Chase experiment
    and its importance.
    • How virus works.
    • Experiments established that viral DNA enters bacterial cells and is required for synthesis of new viral particles.
  10. The backbones of DNA are made up of what? What are the nucleotide base pairs in DNA and how do they pair up?
    • they are made of Dexoyribosse and phosphate groups.
    • Adenine, Thymine, Guanine & Cytosine.
  11. Who is Rosalind Franklin and what is her
    contribution to the understanding of the structure of DNA?
    she took x ray diffraction photos of DNA that ultimately led to them figuring out the twisted structure.
  12. What are purines? Pyrimidines? True or false: Purines always pair up with other purines while pyrimidines only pair up with other pyrimidines.
    • Purines- A & G
    • Pyrimidines- T & C

    False.
  13. The specific base pairing that occurs in DNA suggests a copying mechanism for genetic material called what?
  14. What is meant by saying that the two
    DNA backbones are complementary?
    when two chains/ bakcbones run antiparallel or in opposite directions.
  15. What kind of model of replication did Watson and Crick support? Why? What are the other two and why were they eventually dismissed?
  16. In what direction does DNA replication take place? What is an origin of replication?
    At the end of each replication bubble is a replication fork. The DNA strand that is being synthesizedtoward the fork is called what?
    The DNA strand that is being synthesized away from the fork is called what?
  17. What role does RNA primer play in DNA replication? Primase? DNA polymerase? DNA ligase? What is an Okazaki fragment? Helicase? Topoisomerase?
    • RNA primer play in DNA replication?
    • Primase? synthesizes RNA primer (starting point for nucleotide assembly by DNA polymerase)
    • DNA polymerase- assemble nucleotides into a chain, remove primers, and fill resulting gaps.
    • DNA ligase- closes remaining single- chain nicks.
    • Okazaki fragment- arre first formed on lagging stand 100-2000 nucleotides.
    • Helicase- unwinds the DNA (single standed)
    • Topoisomerase- corrects"overwinding" ahead of replication forks by breaking, swiveling and rejoing DNA strands.
  18. True or false: DNA and mRNA can only be synthesized in the 3’ to 5’ direction.

    True or false: When reading a strand of DNA or RNA, you always read in a 5’ to 3’ direction.
    False

    True.
  19. Understand how a leading and a lagging strand
    are synthesized.
  20. What are telomeres and what role do
    they play in aging? In cancer?
    • telomeres- Short, non-coding repetitive DNA sequences.
    • telomerase- is extended time.

    • absence of telmerase activity may be cause of call aging.
    • mosst cancer cells have telomerase to maintain telomere length and resist apoptosis.
  21. What is gene expression? What are its 2 stages?
    In which part of the cell do each occur in eukaryotes? How does gene expression differ in prokaryotes vs. eukaryotes?
    • conversion of the information encoded in a gene first into messenger RNA and then to a protein.
    • two stages: transcription & translation

    • Prokokaryotic: has no barrier between transcription and translation.
    • Eukaryotic: does have a barrier called nuclear envelope.
  22. What are the 3 stages of transcription?
    Initiation- promoters siginal initiation. transcript mediate the binding or RNA polymerase and initation. when finished is called transcription initation complex. Tata box- a promoter.

    Elongation- Polymerase untwists the helix. transcripton progesses 60 nucleotides/ sec.

    • Termination:
    • pro- polymerase stops transcription at the end of the terminator.
    • euk- polymeerase continues transcription after the pre- mRNA is cutt off. polymerase falls off.
  23. What are the 3 stages of translation?
    initiation- ribosome assembled with m RNA molecule and initiator methionine-tRNA.

    elongation- amino acids linked to tRNAs added one at a time to growing polypeptide chain.

    termination- new polypeptide released from ribosome; ribosomal subunits separate from m RNA.
  24. What are the 4 nucleotides used in DNA replication? How do they pair up?
    What are the 4 nucleotides used in RNA synthesis? How do they pair up?
    • DNA- A, T, G, C
    • RNA- U, A, C, G
  25. True or false: During translation, DNA gives its genetic message to RNA which is then processed
    further to make mRNA.
  26. How do genes dictate phenotypes?
  27. Describe Beadle and Tatum’s famous experiment and its significance. How was their hypothesis later modified?
    • mutation affecting biochemical pathways.
    • neurospora- bread mold.
    • led to the one gene- one enzymes hypotheis.
    • later- one gene- one poly pepide chain hypothesis.
  28. Cells are governed by a cellular chain
    of command, also known as the “flow of genetic information”. What is it?
    Central Dogma- a flow chart.
  29. In eukaryotes, what separates transcription from translation?
    Nuclear Envelope.
  30. How many bases correspond to an amino acid? Are the amino acids based on the codons? Or the anticodons? Where are codons found? Where are anticodons
    found?
    • amino acids are based on the codons.
    • Codons are found on messenger RNA, while anticodons (complementary to codons) are found on transfer RNA.
  31. In which organelle does translation
    occur? In what part of the cell does
    translation occur? What is the result of
    translation?
    the ribosome.

    the end result is that it made a new polytide chain.
  32. In which direction do you read a codon?
    What is the genetic code?
    Is it universal?
    Is it possible to transplant genetic code
    from a firefly into a tobacco plant resulting in a glowing plant?
    • 5'-3'
    • triplet code- a series of nonoverlapping, three-nucleotide words.
    • yes.
  33. Know the following parts of transcription and what they do: RNA polymerase, promoter, terminator,
    transcription unit, template strand, transcription factors, transcription initiation complex, TATA box. What is meant by “downstream”?
    downstream- stars at 3' end.
  34. What is an Intron? Exon? What is the functional and evolutionary significance of an intron?
    • Intron- noncoding regions.
    • exons- the other regions because the are expressed.
  35. True or false: each molecule of tRNA is identical since they all carry amino acids to the ribosomes.
  36. What modifications are made to the pre-mRNA before it can make its journey to the ribosome for translation? (Be sure and understand: 5’cap, poly-A tail, RNA splicing). Give 3 reasons why the
    RNA needs to be modified before it can be called the mRNA.
    modification- the seem to facilitate the export of mRNA out of nucleus. protect mRNA from hydrolytic enzymes. Help ribosomes attact to 5' end.
  37. True or false: each molecule of tRNA is identical since they all carry amino acids to the ribosomes.
  38. Describe the process of translation. What role does the ribosome play? The mRNA? The tRNA? What is the
    result of translation?
  39. What is a polyribosome? What is a free ribosome,
    what does it do and where is it found?
    What is a bound ribosome, what does it do and where is it found?
    • Free ribosome- floating in the cytosol. make cytosolic proteins.
    • Bound ribosome- are attached to the rough ER.
  40. True or false: ribosomes are not identical since some are found floating freely in the cytoplasm while others are stationary on the ER.
    FALSE.
  41. Define mutation.
    What is a point-mutation? Give an example of a well-known disorder
    caused by a point mutation. Name 2 types of point mutations.
    MUTATION- A change in or the process of changing, e.g. nature, form or quality.

    • point mutation- A mutation in DNA or RNA molecule involving a change of only one nucleotide base.
    • (base substitution)

    missense mutation and nonsense mutation.
  42. What do missense mutations generally result in?
    What do nonsense mutations general result in?
    • missense- a different amino acid.
    • nonsense- a stop codon.
  43. What is a frameshift mutation? Why is it often devastating to the organism?
    • one or two nucleotide pairs are inserted into or deleted from the molecule...
    • this will mutate an organism.
  44. True or false: a gene is a region of DNA whose final product is either a polypeptide or an RNA molecule.

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