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16 Cards in this Set
- Front
- Back
define nucleoside
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- sugar plus the nitrogenase base with an OH off of the 5' carbon
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define nucleotide
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- sugar plus the base and hposphate off of the 5' carbon
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What is B DNA?
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- smooth right-handed helix
- major and minor groove - most solvents and proteins work on the major groove by recognizing base pairs |
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What is Z DNA?
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- Left handed helix
- elongated conformation - no major/minor grooves |
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What are teh 3 classes of DNA sequence organization based on sequence repeat?
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1) single-copy DNA sequences
2) moderately reiterated DNA sequences 3) highly reiterated DNA sequences |
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Single copy DNA sequences
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- 60% of human genome made of unique nucleotide sequences
- codes for specific proteins and regulator sequences |
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Moderately reiterated DNA sequences
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- ~30% of human genome
- genes from gene families - histone and rRNA-coding sequences - transposable elements |
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highly reiterated DNA sequences
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-5-10% of genome
- short DNA sequences repeated thousands of times - telomeres, centromeres, ALU |
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DNA polymerase I
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- 5' to 3' activity
- degrade DNA from 3' or 5' end - reverse direction to proofread |
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DNA polymerase III
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- 5' to 3' activity
- reverse direction to remove misincoporated nucleotide (3' exonuclase) for unpaired nucleotides - more more processive than polymerase I |
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Which strand is associated with Okazaki fragments?
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- lagging strand (3' to 5')
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What is primase?
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- DNA polymerase requires a 3' OH primer
- completely new, single-stranded template, primase adds a primer |
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What does helicase do?
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- binds single-stranded DNA in front of replication fork and separate DNA strands via ATP reaction
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What are topoisomerases?
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- untwist supercoiled DNA
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Topoisomerase I
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- catalyses relaxation of supercoiled DNA
- changes DNA linking number by 1 -breaks 1 strand at a time |
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Topoisomerase II
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- catalyzes relaxation of supercoiled DNA
- changes DNA linking number in steps of 2 - breaks 2 strands at a time, 2 points of intersection |