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Biomed > biochem 7A - DNA structure, replication, and repair > Flashcards

biochem 7A - DNA structure, replication, and repair Flashcards

1
Q

what bond links polymers of deoxyribonucleoside monophosphates

A

covalent 3-5 phosphodiester bonds

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2
Q

3-5 phosphodiester bonds are cleaved by what

A

nucleases
(deoxyribonuelases for DNA)
(ribonucleases for RNA)

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3
Q

strands of DNA are held together by what type of bonds

A

H-bonds

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4
Q

AT how many H bonds

A

2H bonds

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5
Q

GC how many H bonds

A

3H bonds

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6
Q

when would a DNA strand have higher melting temp

A

more GC base pairs

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7
Q

hands of DNA

A

A (right handed)
B (right handed)
Z (left handed)

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8
Q

in prokaryotic DNA syntehsis, what base pairing is it almost exclusively that faciliate melting

A

AT base pairs

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9
Q

DnaA protein

A

binds to origina and causes the AT rich regions to melt

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10
Q

DNA helicase

A

undwinds the double helix

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11
Q

ssDNA-binding proteins

A

keeps the strands apart and protect DNA from nucleases that degrade ssDNA

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12
Q

topoisomerase 1

A

cut and rejoin one strand of double helix to remove supercoils

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13
Q

topoisomerase II

A

cuts and rejoins both

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14
Q

what direction does DNA polymerase read

A

3’ -> 5’

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15
Q

what direction does syntehsis occur

A

5’->3’

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16
Q

RNA primer catalzyed by what

A

primase

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17
Q

RNA primer charactieristics

A

~10 nucleotide w free OH on 3’ end

18
Q

chain elongation in prokaryotic DNA synthesis is catalzyed by what

A

DNA polymerase III

19
Q

how does DNA pol III correct mismatch

A

has 3’-5’ exonuclease

20
Q

RNA is excised and the gap is filled by

A

DNA pol I

21
Q

how does eukaryotic DNA replication differ from prokaryotic

A

-has multple origins of replication
-RNA primers are removed by RNase rather than DNA polymerase

22
Q

G1 phase

A

cell prepares to initiate DNA synthesis, biosynthesis occurs (growth)

23
Q

S phase

A

DNA content doubled (DNA synthesis)

24
Q

G2 phase

A

biosynthesis for mitosis to occur (growth and preparation for mitosis)

25
Q

DNA pol alpha

A

-contains primase
-initiates DNA synthesis

26
Q

DNA pol gamma

A

replicates michondria DNA

27
Q

DNA pol delta

A

elongates okazaki fragments of the lagging strand

28
Q

DNA pol epsilon

A

elongates the leading strand

29
Q

telomeres

A

-consist of several thousand tandem repeats of noncoding AGGGTT
-GT strand longer than its complement leaving a few hundred nucleotides in length at the 3’ end
-complexes of noncoding DNA plus proteins located at the end of linear chromosomes
-maintain structural integrity of the chromosome, preventing attack by nucleases
-allow repair enzymes to distinguish between a true end from a break in dsDNA
-in normal somatic cells, telomeres shorten with each successive division (once they shortened beyond a critical length, cell no longe table to divide and is said to be senescent

30
Q

what cells has telomerase and what does it do

A

stem and cancer cells
maintains telomeric length in the cells

31
Q

reverse transcriptase function

A

enzyme that syntehsizses DNA from RNA

32
Q

are histones basic or acidic

A

basic

33
Q

nucleosomes

A

order DNA in structural units

34
Q

nucleosomes further arranged into what

A

chromosomes

35
Q

DNA damage

A

-hydrolysis
-oxidation
-methylation
-UV light
-ionizing radiation

36
Q

UV light leads to the formation of what

A

pyrimidine dimers (thymine dimers)

37
Q

Base Excision Repair (BER)

A

removes and replaces individual damaged bases

38
Q

Nucleotide excision repair (NER)

A

-removes and replaces damaged bulky lesions (2-30 nu)
-recognizes physical distortion rather than specific base sequences
(larger area)

39
Q

mismatch repair

A

removes nu that do not form correct base pairs

40
Q

Xeroderma pigmentosum (DNA repair disease)

A

-pyrimidine dimers formed in skin cells exposed to UV light
-defects in excision repair due to a mutant UV-specific endonuclease

41
Q

ataxia telangiectasia

A

-defects in excision repair
-neurodegenerative disease
-poor coordination

Biomed (18 decks)

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