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MCAT - Bio/BC > 1B > Flashcards

1B Flashcards

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1
Q

nucleotide vs nucleoside

A 
nucleoTide = base + sugar + phosphate
nucleoside = base + sugar
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2
Q

dna backbone is made of

A

pentose sugar and phosphate group

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3
Q

what are the pyrimidines? purines?

A

purine s= Adenine, thymine (1 ring)

pyrimidine = Cytosine, Uracil, Threonine (2 rings)

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4
Q

how many hydrogen bonds between AT? GC

A

2 in AT

3 in GC

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5
Q

which is stronger? GC or AT

A

GC

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6
Q

define:
denaturation
reannealing
hybridization

A

denature - unwinds the 2 strands (ex. high temp)
reanneal - puts them back together
hybridizayion - a single strand will readily bind another single strand

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7
Q

Dna gyrase is what class of topoisomerase? what does it do?

A 
class 2 topoisomerase
uncolis DNA AHEAD of replication fork
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8
Q

helicase

A

unwinds dna AT replication fork i.e. separates DNA

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9
Q

Single-strand binding protein (SSB)

A

keeps DNA unwound by stopping reannealing

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10
Q

SSBs stabilize ssDNA by

A

binding to it

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11
Q

all biological dna synthesis occurs from what end to what end

A

5’ to 3’

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12
Q

primase

A

lays down short RNA primer on unwound DNA

-the RNA primer is complimentary to DNA

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13
Q

dna polymerase

A

makes DNA that’s complimentary to unwound dna

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14
Q

synthesis that proceeds in direction of replication fork

A

leading strand

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15
Q

synthesis that proceeds in opposite direction of replication fork

A

lagging strand

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16
Q

which strand, leading or lagging, has okazaki fragments

A

lagging

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17
Q

what stitches okazaki fragments together

A

dna ligase

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18
Q

T/F: DNA synthesis is unidirectional

A

false - bidirectional, 2 replication forks form and work in opposite directions

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19
Q

______ has proofreading activity that corrects mistakes

A

dna polymerase

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20
Q

which DNA polymerase removes RNA primers

A

DNA polymerase 1

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21
Q

how many times does replication happen in a cell generation? during what phase(s)

A

once

S phase

22
Q

is dna replication conservative, semi-conservative, or dispersive

A

semi-conservation bc there’s intermediate weights

23
Q

telomerase

A

catalyzes lengthening of telomeres

has molc of RNA that serves as a template for new telomere segments

24
Q

nuclease

A

cuts out unwanted or defective segments of nucleotides in DNA sequence

25
Q

enzyme that relieves the winding strain generated during unwinding of double helix by creating a single strand nick in the DNA

A

topoisomerase

26
Q

holds the replication fork of dna open so it can get ready for synthesis

A

single strand binding protein

27
Q

Prokaryotes or eukaryotes:

has multiple origins of replication

A

eukaryotes have multiple origins

prokaryotes have a single origin for their circular dna

28
Q

what enzyme has 3’ to 5’ exonuclease activity

A

DNA polymerase with it’s proofreading activity bc it will backup and replace the incorrect nucleotide with the right one

29
Q

mismatch repair

A

enzyme recognizes incorrect pairing and cuts out the dna with the mismatch –> polymerase readds the right nucleotides

30
Q

how do repair enzumes during mismatch repair know which strand of DNA to cut

A

it cuts the DNA strand that does NOT have methylations bc it takes some type after replication for new strands to have methylation

31
Q

damaged base gets cut out –> base’s sugar-phosphate backbone gets cut out –> more nucleotides next to base get cut out –> polymerase remakes the cut-out nucleotides

A

base-excision repair

32
Q

nucleotide-excision repair

A

damaged nucleotide gets cut out then polymerase replaces it

33
Q

nick translation

A

polymerase chews off bad nucleotides and replaces them with new nucleotides
-I’m confused about difference to nucleotide exciison repair

34
Q

SOS response in E Coli when there’s too much DNA damage

A

polymerase replicates over the damaged DNA like it’s normal by using damaged dna as template

35
Q

caps on the ends of chromatids which protects DNA from deterioration

A

telomeres

36
Q

which strand of dna is synthesized in a discontinuous fashion

A

lagging strand

37
Q

pieces of newly synthesized dna on the lagging strand

A

okazaki fragments

38
Q

when is genetic material lost from telomeres

A

during the joining of okazaki fragments

39
Q

(EUk or Prokaryotes) have 60S and 40S ribosome subunit

(EUk or Prokaryotes) have 50S and 30S ribosome subunit

A

Euk - 60, 40

Pro- 50, 30

40
Q

noncoding region of dna ____

coding region of dna ___

A 
noncoding = intron
coding = exon
41
Q

reverse transcriptase

A

catalyzes the synthesis of DNA from RNA

42
Q

dna synthesis from polymerase and reverse transcriptase are in what direction

A

5’ to 3’ bc all dna synthesis is through this way

43
Q

what strcture:

  1. site of cellular respiration
  2. cell trashcans
  3. site of translation from mRNA to protein
  4. involves glycosylation
A
  1. mitochondria
  2. lysosomes
  3. ribosomes
  4. golgi apparatus
44
Q

cleave specific sequences of DNA

A

endonuclease

45
Q

how many codons? how many AAs?

A

64 codons
21 Amino acids
so many diff codons may code for the same AA

46
Q

where does translation occur

A

ribosomes

47
Q

where does transcription occur

A

nucleus

48
Q

where are ribosomes abundant?

A

cytosol & rough endoplasmic reticulum

49
Q

tRNA binds to ____ to be used in ____

A

ribosomes to be used in translation

50
Q

translation occurs within the

A

cytosol

51
Q

amino acids are linked by what bonds

A

peptide bonds

52
Q

Covalently linked nucleotides constitute the ______ bonds in DNA.

A

phosphodiester

MCAT - Bio/BC (3 decks)

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