Download Ch. 16 Molecular Basis of Genetics

CH. 16 STUDY GUIDE : DNA STRUCTURE AND REPLICATION
KEY TERMS
James D. Watson
Francis H.C. Crick
DNA
RNA
transformation
bacteriophage
purine
adenine
guanine
pyrimidine
thymine
cytosine
nucleotide structure
sugar
nitrogenous base
phosphate
carbons 1'-5'
hydrogen bonds
double helix
antiparallel strands
semiconservative replication
helicases
topoisomerases
RNA primer
primase
DNA polymerase
leading strand
lagging strand
Okazaki fragments
DNA ligase
proofreading
excision repair
WORD ROOTS
helic - = a spiral (helicase: an enzyme that untwists the double helix of DNA at
the replication forks)
liga - = bound or tied (DNA ligase: a linking enzyme for DNA replication)
-phage = to eat (bacteriophages: viruses that infect bacteria)
semi - = half (semiconservative model: type of DNA replication in which the
replicated double helix consists of one old strand, derived from the old molecule,
and one newly made strand)
telos - = an end (telomere: the protective structure at each end of a eukaryotic
chromosome)
trans - = across (transformation: a phenomenon in which external DNA is
assimilated by a cell)
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QUESTIONS
1. Draw a nucleotide, point out the phosphate, sugar and the base. Indicate
whether the base is a purine of pyrimidine and whether the nucleotide is from
DNA or RNA.
2. Name the four nitrogenous found in DNA, and indicate which are the purines
and pyrimidines (Hint: Look for the terms with”y” in them.).
3. Draw a diagram of DNA, point out the 5' and 3' ends of each chain. Also point
out an individual nucleotide, and its three components. Indicate how many
hydrogen bonds there are in a C-G pair and an A-T pair.
4. Given a sequence of bases in one strand of DNA, (atcgaacgt) give the
sequence in the complimentary strand.
5. Explain how the Watson-Crick model accounts for the precise replication of
DNA.
6. Describe how repair enzymes act to correct mutations and errors that occur
during replication.
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