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MCAT Biology > Class 3 > Flashcards

Class 3 Flashcards

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1
Q

What is a nucleotide composed of?

A

Sugar (ribose or deoxyribose)
Base
Phosphate

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2
Q

What is the difference between ribose and deoxyribose?

A

Deoxyribose is missing 2OH

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3
Q

On a nucleotide where does the base attache?

A

At the 1 carbon

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4
Q

On a nucleotide where does the phosphate attach?

A

At OH group 5’ carbon

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5
Q

What is a nucleoside?

A

Sugar and base only, no phosphate

-can specify the number of phosphates (ATP,UDP)

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6
Q

What does the 3’OH attack of a nucleotide?

A 
#1 phosphate and leaving group is pyrophosphate
-forms phosphodiester bond between 2 nucleotides
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7
Q

What way does polymerization happen in a nucleotide?

A

5’ to 3’ synthesis and base sequence.

-the strands are anti parallel and complimentary and held together by H bonds

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8
Q

What is a pyrimidine?

A

CUT (cyclohexane)

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9
Q

What is a purine?

A

GA (cyclohexane with cyclopentane)

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10
Q

What is another word for separation?

A

Denaturing and melting

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11
Q

What is another word for complimentary binding?

A

Hybridization and annealing

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12
Q

What is a genome?

A

All DNA in an organism

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13
Q

What kind of DNA foes prokaryotes have?

A

Have circular DNA in cytosol

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14
Q

What can degrade prokaryote DNA?

A

Endonuclease

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15
Q

How can prokaryotic DNA avoid degradation?

A

Methylate the DNA so the endonuclease doesn’t fit

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16
Q

What does DNA gyrase?

A

Causes super coiling of DNA

-makes endonuclease not able to come in

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17
Q

What does eukaryote DNA look like?

A

Several linear chromosomes in a nucleus and wrap around histone proteins

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18
Q

How does DNA wrap around histone?

A

At pH7 the AAs that are basic will be + the phosphate on DNA is -

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19
Q

What is euchromatin?

A

DNA unwound, active to be transcribed (has more transcription)
-light staining

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20
Q

What is a heterochromatin?

A

Tightly wound, inactive and dark staining (has more histones)

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21
Q

What is a centromere?

A

Where 2 replicated stands of DNA (sisterchromatids) are held together
-also where mitotic spindle attaches (repeated sequence area)

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22
Q

What are telomeres?

A

Ends of linear chromosomes are short sequences repeats TTAGGG and stabilize the ends of the chromosomes

  • degraded over time
  • dont code for anything
  • can base pair with itself to avoid degradation
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23
Q

What is the central dogma?

A

DNA>RNA>Proteins

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24
Q

What are the exceptions to the central dogma?

A

Reverse transcriptase and non coding RNA where they r transcribes into proteins (RNA Final product)

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25
Q

What is the starting codon?

A

AUG = methionine

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26
Q

What is the stop codon?

A

UAA
UGA
UAG
-doesnt code for anything

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27
Q

How many chromosomes does the human genome have?

A

46 chromosomes

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28
Q

What are point mutations?

A

Single base pair change

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29
Q

What are the 3 point mutations?

A

Missense: codon for 1 AA because a new codon for AA
Nonsense: codon for AA becomes a Stop codon
Silent: Codon for AA becomes new codon for some AA

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30
Q

Which silent change is worse?

A

Change in 3rd position is normally silent

2nd Position change almost always a different AA

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31
Q

What is a frameshift mutation?

A

Insertion and deletion changes the reading frame

-dont get this when they occur in multiples of 3

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32
Q

What are sources of mutations?

A 
Polymerase errors
Endogenous Damage
RGS
Physical Damage
Exogenous Damage
Radiation
Chemicals
Transposons
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33
Q

What do Polymerase errors cause?

A

Point mutation
Small repeats
Insertion and deletion

34
Q

What do Endogenous Damage errors cause?

A

Oxidative DNA

Crosslinked basses

35
Q

What do RGS/Physical Damage errors cause?

A

Double or single stranded breaks, lead to polymerase errors

36
Q

What do Exogenous Damage errors cause?

A

UV- pyrimidine dimers (CUT)
Chemicals can lead to physical damage
Polymerase errors
Xray- double stranded breaks

37
Q

What do transposons (jumping genes) errors cause?

A

Insertion/deletion
Inversions
Duplications

38
Q

What do transposons do?

A

Cut and paste enzyme and surrounded by inverted sequence repeat on each side

39
Q

What are the 3 different kinds of transposons?

A

IS element
Complete transposons with genes
Composite transposons
-if put in the middle of a coding region it can no longer be expressed

40
Q

What are the 2 different kinds of chromosome rearrangements?

A

Same direction: Can base pair with themselves and delete a gene be degraded our reinsert somewhere else

Opposite direction: can. base pair with themselves and leads to inversion of gene

-can result in amplification and therefor get more protein

41
Q

What are polymerase errors?

A

Repaired by mismatched repair path (after replication)

-take out incorrect base and replaces with correct one

42
Q

How do polymerase know which strand to repair?

A

daughter strand its not methylated so that’s how they know which copy is right

43
Q

What is endogenous and exogenous damage repaired by?

A

Base excision repair and can happen anytime

-it identifies damaged base, takes tout and replaces it with same base just not damaged

44
Q

What does homology dimated repair?

A

Repairss DS breaks and uses sister chromatid as template

-happens at the end of G2 or wherever you have sister chromatids

45
Q

What is non homologous end joining ?

A

Np template just cleanse it up and sticks it back together (DS)
-this is mutagenic

46
Q

What is a translocation?

A

Due to faulty DNAP repair (nonhomologous end joining) or abnormal recombination

47
Q

How do you fix pyrimidine dimers?

A

Directly reverse by exposing to white light

48
Q

what can transposons be repaired by?

A

Nothing

49
Q

What are characteristics of DNA Replication?

A

Semiconservative
Replication Happens 5’ to 3’ OH
Needs a primer made from RNA
Requires a template DNA

50
Q

What dopes helices do?

A

Separates the DNA strands

51
Q

What does topoisomerase do?

A

Relaxes supercoiling on either end of the replication bubble

52
Q

What does DNA polymerase do?

A

Replicate DNA and removes primers with DNA

53
Q

What does ligase do?

A

Links Okazaki fragments

54
Q

How many replications are in prokaryotes and eukaryotes?

A

Prokaryotes only have 1 replication

Eukaryotes have more than one

55
Q

What does DNA pol 3 do?

A

High processivity and fast
5’ to 3’ polymerase and 3’ to 5’ exonuclease
Break phosphodiester bond at the end of DNA
Has proofreading abilities
Starts 400 base pairs down of ORI

56
Q

What does DNA pol 1 do?

A

Low processivity and slow
5’ to 3’ and 3’ to 5’ to exonuclease
5’ to 3’ to removes the primer and adds nucleotides to primer
DNA exception pair

57
Q

What does DNA 2 do?

A

5’ to 3’ and 3’ to 5’ exonuclease
Back up for DNA pol 3
Does DNA repair

58
Q

What does DNA pol 4 and 5 do?

A

Error prone 5’ to 3’

DNA repair but fast

59
Q

How many origins and bubbles doo eukaryotes have?

A

Multiple origins and multiple bubbles

60
Q

In eukaryotes how are primers added?

A

RNA primers added to the 3’end of parent strand

-lagging has SS DNA where it is degraded leading to smaller telomeres

61
Q

What are telomerase?

A

Elongated telomeres on parent strand
Carries own RNA template
Has reverse transcriptase activity (RNA>DNA)

62
Q

What are immortal cells?

A

Are resistant to decrease in telomeres and expresses telomerase always
(sperm and cancer cells)

63
Q

What are the characteristics of DNA?

A 
DS
Helix
Thymine
Deoxyribose
One type
64
Q

What are the characteristics of RNA?

A 
SS
3D Shapes 
Uracil
Ribose
Multiple types
65
Q

What is hnRNA?

A

Heterogenous nuclear RNA
Initial unprocessed transcript will become mRNA
-this is only in eukaryotes

66
Q

what are miRNA and siRNA?

A

Complimentary to mRNA and bind mRNA ro make DS mRNA so it cant be translated and regulates translation

67
Q

In transcription what kind of mRNA is being formed?

A

it is complimentary/antisense strand to template and identical lens strand to coding

68
Q

What are the 2 kind of DNA binding proteins?

A

Repressor: bind DNA but make it harder for DNA polymerase to bind activators

Activators: bind to enhancers and help recruit RNA polymerase and help increase transcription

69
Q

What do prokaryotes have that eukaryotes do not?

A

operators

70
Q

What is characteristic of prokaryote transcription/translation/replication?

A

Transcription and translation happen at the same time
No mRNA processing, it can be immediately translated
Polycistronic
1 RNA polymerase

71
Q

What is characteristic of eukaryotes transcription/translation/replication?

A

Transcription and translation dont happen at the same time
MRNA is processed from hnRNA>mRNA then 5’ G cap to get out of nucleus, 3’ poly a tail is stop sit, splicing introns and exons
Monosistronic (1 gene 1 protein)
Multiple RNA polymerases

72
Q

How are AAs attached?

A

at the 3’ end of tRNA

73
Q

What is the anticodon complimentary too?

A

mRNA

-UAC on tRNA to AUG on mRNA

74
Q

What can the 3rd codon normally be?

A

Wobbly, so its more likely to change

-happens when there is a GU or I at the end of the anticodon

75
Q

What is and aminoacyl tRNA?

A

tRNA binds to it AA

-an=minoacyl synthase attache AA to tRNA, have 1 for every tRNA and this costs 2 ATP

76
Q

What is thee difference between ribosomes in prokaryotes and eukaryotes?

A

Prok: 50S large SU, 30S small SU

Eukaryote: 60S large SU, 40S small SU

77
Q

what is the flow to make proteins?

A

A to P to E

78
Q

What are the different sites in the ribosome?

A

A: new AA added
P: Growing protein help
E: Empty tRNA exit

79
Q

Do tRNA’s recognize stop codons?

A

NO tRNA recognizes stop codon and the release factor binds A site and breaks dont between final tRNA and final AA, releasing completed protein

80
Q

What is the equation for determining how much ATP a protein needs to be formed?

A

AA x 4= #ATP needed

81
Q

What are chaperones?

A

Used by tertiary proteins to help[ them fold

82
Q

What are coolant modifications of proteins?

A

Disulphide bridge
Glycosylation
Phosphrylated

MCAT Biology (9 decks)

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