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MCAT bio > molecular genetics > Flashcards

molecular genetics Flashcards

1
Q

central dogma

A

DNA –> RNA –> protein
- transcription and translation

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2
Q

hershey-chase experiment

A

radiolabeled sulfur and phosphorus to distinguish where genetic info was (protein vs nucleic acids)
- result was radiolabeled phoshporus which is in dna not protein

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3
Q

reverse transcriptase

A

allows dna to be transcribed from rna
- retroviruses
- special kind of dna polymerase that operates with rna template

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4
Q

codon

A

3 dna nucleotides that code for an amino acid
4^3 = 64 combinations

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5
Q

degeneracy

A

multiple codons can make the same amino acid
- increase resistance to error

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6
Q

wobble position

A

provide protection against mutation in the final nucleotide of a codon. most codons are defined by the first two nucleotides

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7
Q

stop codons

A

UGA, UAG, UAA

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8
Q

start codon

A

AUG (met)

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9
Q

watson and crick model of dna

A

dna is a double helix of antiparallel strands with a sugar phsophate backbone
- complimentary basepairing
- interior stabilized by h bonds between bases and hydrophobic interactions between stacked bases

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10
Q

base stacking

A

arrangement of nucleotide nitrogenous bases that allow for hydrophobic interactions`

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11
Q

compliementary dna strands

A

are complimentary and antiparallel (be aware of directionality when looking at question wording)

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12
Q

how is dna organized in eukaryotes

A

linear chromosomes in the nucleus

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13
Q

autosomes

A

22 chromosomes in humans that are somatic cells and have two copies each. 1 maternal and 1 paternal

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14
Q

sex chromosomes

A

two each
female XX
male XY

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15
Q

how is the massive content of dna squeezed into chromosomes

A

histones and chromatin

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16
Q

histones

A

proteins that are wound around dna with subproteins: h1 h2A h2B H3 H4
core: two dimers ofh2a and h2b and a tetramer of h4 and h3
h1: linking unit

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17
Q

nucleosomes

A

dna-histone complex
- beads on a string

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18
Q

chromatin

A

structure formed by nucleosomes (dna and histones)

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19
Q

euchromatin

A

loose configuration that allows dna to be easily transcribed
- during interphase (allows for transcription)

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20
Q

heterochromatin

A

tighly coiled dense form of chromatin that is visible during CELL DIVISION

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21
Q

how do histones and dna interact

A

charge driven interactions
- histones are positive and dna is negative

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22
Q

acetylation of histones

A

reduce their positive charge, and loosen binding on dna allowing for an increase in dna transcription

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23
Q

semiconservative replication

A

dna replication where end product is 1 original strand and one new strand

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24
Q

meselson-stahl experiment

A

experiment that distinguished between old and new dna
they grew radioactive N in e. coli and traced it
- found that dna is semi-conservative

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25
Q

orgin of replication

A

start of dna replication
- one place in prok
- multiple in euk

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26
Q

helicase

A

unwinds dna for transcription
- seperates the strands

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27
Q

single stranded binding proteins

A

keep the strands seperated

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28
Q

primase

A

short rna primer with a free 3’ oh that is used to start dna synthesis

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29
Q

dna polymerase

A

reads dna from 3-5 and synthesizes from 5-3

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30
Q

dna gyrase/ topoisomerase

A

alliviates supercoiling created by helicase

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31
Q

ligase

A

links okazaki fragments on the lagging strand

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32
Q

DNA polymerase direction

A

can only add in the 5’ to 3’ direction and read in the 3’ to 5’

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33
Q

lagging strand

A

made into short sequences by dna polymerase that must be ligated together by ligase

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34
Q

dna polymerase 1

A

prokaryotic dna polymerase that assists with okazaki fragments
- removes rna primer through excision repair

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35
Q

dna polymerase 2

A

primary eukaryotic dna polymerase involved with repair

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36
Q

dna polymerase 3

A

primary eukaryotic polymerase for dna replication

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37
Q

dna polymerase alpha

A

initiates synthesis in replication in both strands

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38
Q

dna polymerase delta

A

takes over from dna polymerase alpha amd adds dna after the rna primer is removed

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39
Q

dna polymerase epsilon

A

extension of leading strand and dna repair

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40
Q

dna polymerase beta

A

dna repair

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41
Q

dna polymerase gamma

A

replicates miDNA

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42
Q

telomerase

A

extends telomeres at the end of eukaryotic chromosomes

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43
Q

what are telomeres

A

repeating sequences at the end of the chromosome that cope with the fact that dna polymerase can’t replicate the end of a chromosome

44
Q

what kind of cells is telomerase active in

A

stem and cancer (not somatic)

45
Q

transcription

A

transcribe dna to rna in the nucleus. results in mrna

46
Q

rna polymerase

A

enzyme that synthesizes pre-mrna during transcription
- synthesizes in the 5’ to 3’ direction

47
Q

promotor region

A

where rna polymerase binds to dna to begin transcription with the assitance of transcription factors

48
Q

TATA box

A

most important promotor in eukaryotes

49
Q

template strand for rna synthesis

A

antisense strand

50
Q

sense strand

A

the non - template strand that corresponds to the codons on the mRNA molecule

51
Q

requirements for dna polymerase

A
  1. always need a template
  2. they add in the 5-3 ‘ direction
  3. they cannot start from scratch (need primer)
52
Q

rna polymerase 2

A

default rna polymerase that synthesizes hn RNA (precursor to mRNA)

53
Q

hnRNA (heterogeneous nuclear)

A

precursor to mRNA that must undergo post-transcriptional modification
1. poly a tail
2. 5’ cap
3. splicing

54
Q

RNA polymerase 1

A

synthesizes ribosomal rna in nucleolous

55
Q

rna polymerase 3

A

synthesizes trna and rRNA

56
Q

does post transcriptional modification of rna occur in prokaryotes?

A

no, only eukaryotic rna experiences poly A tail addition, 5’ cap, and spliciing

57
Q

why does prokaryotic rna not undergo post transcriptional modification?

A

transcription and translation occur simultaneously so there is no time for modification

58
Q

3’ poly A tail

A

string of 250 adenine nucleotides to the 3’ end of the hnRNA
- protects mrna from rapid degredation in the cytosol
- speed of mrna degredation depends on length of the poly A tail

59
Q

5’ cap

A

7-methylguanylate triphosphate cap on the 5’ end of the hnRNA
- prevents premature degredation and prepares the RNA complex for export from the nucleus

60
Q

splicing

A

noncoding (introns) are removed and exons (coding sequences) are left in the RNA and ligated together
- exons exit the nucleus
- exons can be alternatively spliced leading to protein variation
-carried out by the spliceosome and protein complexes –> snRNPs

61
Q

alternative splicing

A

various combinations of exons produced by the splicosome that allows for large variation in protein produces

62
Q

small nuclear ribonuclear proteins (snRNPs)

A

spliceosome + small nuclear RNAs and protein complexes

63
Q

translation

A

process where mRNA is translated into a protein via ribosomes

64
Q

where does translation take place

A

cytosol in both eukaryotes and prokaryotes

65
Q

tRNA

A

small RNA molecule with a hairpin structure that translates between codons and amino acids
- contains anticodon

66
Q

anticodon

A

complementary sequence to the mRNA codon

67
Q

aminoacyl tRNA synthetases

A

charge tRNA with its amino acid by attatching the c terminus of the amino acid to the 3’ end of the tRNA molecule
- requires 2 atp to charge a tRNA and power the formation of the peptide bond

68
Q

is protein synthesis endergonic or exergonic

A

endergonic
- energy consuming

69
Q

large subunit of euk ribosome and prok

A

60s and 50s

70
Q

small subunit of euk ribosome and prok

A

40s and 30s

71
Q

overall ribosome for euk and prok

A

70 and 80s

72
Q

function of small ribosomal unit

A

read the RNA

73
Q

initiation

A

initiator trna binds to the start codon aug and the ribosome is assembled

74
Q

initial amino acid in eukaryotes

A

methionine

75
Q

initial amino acid in prokaryotes

A

N-formylmethionine

76
Q

elongation

A

ribosome reads mRNA from 5’ to 3’ and synthesizes the polypeptide from N to C terminus

77
Q

a site

A

contains the next aminoacyl-tRNA complex

78
Q

p site

A

peptide bond is formed between growing peptide and incoming amino acid

79
Q

e site

A

trna is no longer charged and detaches from the mrna

80
Q

termination

A

stop codon (UGA, UAA, UAG) causes release factors to trigger ribosome disassembly and releases the peptide

81
Q

post translational modifications

A
  1. phosphorylation
  2. glycosylation
  3. protein folding
  4. formation of quartenary structure
82
Q

kinases

A

add phosphates

83
Q

phosphotases

A

remove phosphates

84
Q

chaperone proteins

A

assist in protein folding

85
Q

cleavage

A

cleaving prehormones before they can become active

86
Q

point mutation

A

one nucleotide base is wrong

87
Q

silent mutation

A

missense mutation where the amino acid does not change

88
Q

conservative mutation

A

a type of missense mutation where there is a new amino acid with similar properties

89
Q

non-conservative mutation

A

missense mutation where amino acid change is large

90
Q

nonsense mutation

A

premature stop codon

91
Q

frameshift mutation

A

add/delete amino acid and codons downstream are altered

92
Q

chromosomal deletion

A

missing a large part of a chromosome

93
Q

chromosomal duplication

A

adding extra to chromosome

94
Q

inversion

A

segment is reversed , usually harmless

95
Q

translocation

A

genes switch places

96
Q

insertion

A

move between chronosomes

97
Q

transopons

A

non-coding genetic info that can move between chromosomes

98
Q

anueploidy

A

too few or too many sets of chromosomes resulting from nondisjunction during cell division

99
Q

monosomy

A

1 copy of chromosome

100
Q

trisomy

A

3 copies of a chromosome

101
Q

DNA excision repair

A

3’ to 5’ endonculease activity

102
Q

Mutagens

A

Agents that damage dna, usually carcinogens

103
Q

Base excision repair

A

Small scale errors like mismatched pairs

104
Q

Nucleotide excision repair

A

Larger lesions of dna, thymine dimers

105
Q

Which interphase checkpoint protects against anueploidy

A

M phase checkpoint

MCAT bio (12 decks)

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