Genetics Chapter 9

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cl165515
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Genetics Chapter 9
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2012-07-16 19:57:29
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Genetics Chapter 9
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  1. Molecular genetics
    the study of DNA and RNA structure and function at the molecular level
  2. Criteria for genetic material
    • information
    • transmission
    • replication
    • variation 
  3. nucleic acid structure
    nucleotide linked together in a linear manner to form a strand of DNA and RNA

    double helix (DNA)

    3D structure of DNA results from folding and bending of the helix
  4. nucleotide
     
    the repeating structural units of nucleic acids
  5. three components of nucleotides
    • phosphate group
    • pentose sugar
    • nitrogenous base 
  6. deoxyribose lacks a ______ group at the __ position when compared to ribose, the sugar of RNA
    • hydroxyl group
    • 2' 
  7. purines
    • adenine
    • guanine  
  8. pyrimidines
    • uracil
    • cytosine
    • thymine 
  9. nucleoside
    • base attached only to a sugar (deoxyribose vs. ribose)
    • i.e. deoxyadenosine, deoxyguanine 
  10. nucleotide
    a nucleoside with one or more phosphate groups covalently attached to the 3' and/or 5' hydroxyl group
  11. examples of a nucleotide
    • adenosine triphosphate (ATP)
    • adenosine diphosphate (ADP)
    • adenosine monphosphate (AMP)
  12. attachment sites of base pairs and phosphate to sugar
    • base is attached to the 1' carbon 
    • one or more phosphate groups attach at the 5' carbon 
  13. phosphodiester linkage
    a linkage between two carbons and a phosphate group through two oxygens
  14. phosphodiesters are formed though______ and form much of the backcone of _____ and _____.
    • dehydration synthesis
    • DNA
    • RNA
  15. DNA and RNA backbone is ____ charged.
    negatively
  16. specific sequence of nitrogenous bases
    • 5' to 3' direction
    • 5'-TAGCGAAT-3' complementary strand would be 5'-ATTGCGTA-3'
  17. nucleotides within a strand are covalently bonded together to prevent___
    shuffling or rearrangement of sequences
  18. Linus Pauling
    • 1950's
    • proposed alpha helix as a secondary structure of some proteins
  19. Edwin Chargaff
    • 1950
    • worked with the chrmical compostion of DNA
    • discovered the amount of A=T and C=G
    • "Chargaff rule"- always an equal amount of A to T and C to G
  20. Rosalind Franklin
    • 1951
    • X-ray diffraction of DNA was consistant with a helical structure
    • diameter too wide to only be single stranded helix
    • suggested DNA was composed of 2 or more strands with 10 bases per turn
    • died of ovarian cancer from the radiation from her work 
  21. Maurice Wilkins
    • assistant was Rosalind Franklin
    • took Franklin's work to Watson and Crick and put the pieces together and were awarded the 1962 Nobel Prize for the discovery of the double helix DNA molecule
  22. key features of DNA helix
    • double stranded
    • 10 base pairs within a complete twist 360o around the backbone
    • stablilized by hydrogen bonding between base pairs  
  23. AT/CG rule (Chargaff's rule)
    • purines (A & G) will always bond with pyrimidines (T & C)
    • keeps width of double helix consistant
    • DNA strands are complementary to each other
    • knowing the sequence on one strand allows us to predict the sequence of its complementary strand 
  24. G & C have ___ hydrogen bonds while A & T have ___ hydrogen bonds.
    • three
    • two 
  25. backbone 
    • sugar and phosphate group
    • outer surface in direct contact with water 
  26. groove
    indentation where the atoms of the bases are in contact with surrounding water 
  27. B DNA
    • right handed twist
    • predominant in living cells
    • wild type
    • 10 base pairs per 360o turn
    • bases tend to be centrally located
    • hydrogen bonds between base pairs occurs perpendicular to central axis  
  28. A- DNA
    • right handed twist
    • 11 base pairs per 360o turn
    • more tightly round
    • hydrogen bonds between base pairs are tilted
    • occurs under low humidity conditions
    • not biologically significant in DNA 
  29. Z DNA
    • left handed twist
    • zigzag appearence to it
    • 12 bases per 360o turn
    • more tilted than A-DNA
    • occurs at high ionic strength (high salt concentration)
    • sequence aternat between purines and pyrimidines
    • at lower ionic strenths methylation of cytosine bases favors Z DNA
    • recently determined to be biologically important 
  30. triplex DNA
    • triple helix
    • synthetic DNA that binds into the major grooves of natural double-stranded DNA in a sequence specific way
    • T in synthetic DNA will bind to an AT pair inthe natural DNA strands
    • used as a way to silence genes like cancer to try to turn it off
  31. associated proteins
    DNA-binding proteins are necessary to help compact chromosomal DNA in order to fit into a living cell 
  32. RNA structure 
    • shorter than DNA
    • one strand of DNA is used as a template to make one complementary copy of single stranded RNA during transcription
    •  

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