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Biology > 8. DNA+ Protein synthesis > Flashcards

8. DNA+ Protein synthesis Flashcards

1
Q

how many genes are found in mitochondrial DNA?

A

37

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2
Q

which enzymes twist and close the ends of a double-twisted DNA?

A

topoisomerase I and topoisomerase II

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3
Q

how is prokaryotic DNA put inside since they have no histones?

A

through supercoils

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4
Q
A

DNA-polymerase III (poly III)

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5
Q

the function of nucleases

A

enzymes that clave (split/divide) phosphodiester bonds in a nucleic acid

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6
Q

the function of endonucleases

A

cleave internal phosphodiester bonds

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7
Q

the function of exonucleases

A

remove nucleotides from the 5’ or the 3’ end

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8
Q

does helicase require ATP?

A

yes

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9
Q

what is the replicative helicase in E. coli called?

A

dnaB protein

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10
Q

which RNA is unstable?

A

mRNA

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11
Q

role of topoisomerase

A

untwists the helix form of DNA

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12
Q

role of helicase

A

recognizes the origin of replication and breaks hydrogen bonds by using ATP

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13
Q

what is the point where replication starts called?

A

replication fork

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14
Q

leading strand

A

3’ to 5’

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15
Q

lagging strand

A

5’ to 3’

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16
Q

SSB proteins

A

single-stranded binding proteins

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17
Q

role of SSB proteins

A

bind to the untwisted strands to keep them separated

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18
Q

in which phase are chromosomes most dense and in the shortest form?

A

metaphase, where chromatin is fully condensed

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19
Q

which form of chromatin is more dense and compacted?

A

heterochromatin

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20
Q

where are TELOMERS found?

A

at the ends of eukaryotic chromosomal DNA

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21
Q

what are telomeres?

A

special nucleotide sequences, with noncoding genes

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22
Q

functions of telomeres

A
  1. act as a buffer zone to postpone (not prevent) gene erosion at the ends of the DNA
  2. prevent the STAGGERED ENDS of daughter DNA molecules from activating transduction pathways, which can lead to the cell’s self-destruction
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23
Q

which enzyme keeps DNA from supercoiling during replication?

A

topoisomerase

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24
Q

At which end does PRIMASE synthesize PRIMERS?

A

at the 3’ end

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25
Q

which enzyme takes away primers?

A

exonuclease

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26
Q

In which direction does DNA-polymerase III run?

A

always 5’ to 3’

(moves along the old template strand in the 3’ to 5’ direction)

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27
Q

role of DNA ligase?

A

joins together Okazaki fragments of the lagging strand

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28
Q

which enzyme replaces RNA nucleotides of the primers with DNA nucleotides?

A

DNA polymerase I

29
Q

which type of polymerases do prokaryotic cells contain?

A

DNA polymerase I
DNA polymerase III

30
Q

which type of polymerases do eukaryotic cells contain?

A

DNA polymerase I
DNA polymerase III
alpha polymerase
delta polymerase
epsilon polymerase

31
Q

stems

A

base-paired portions in RNA molecules

32
Q

loops

A

unpaired portions in RNA molecules

33
Q

which DNA strand is transcribed?

A

3’-5’

34
Q

which enzyme unwinds DNA and transcribes the material to RNA?

A

RNA polymerase II

35
Q

what is the condition that must be fulfilled so that RNA polymerase II can start its work?

A

A transcription factor must attach to the promoter

36
Q

TATA box

A

important promoter DNA sequence

37
Q

what is used in prokaryotes instead of a transcription factor?

A

a SIGMA factor

38
Q

in what direction does mRNA elongate?

A

in the 5’-3’ direction

39
Q

termination (transcription) in eukaryotes

A

RNA polymerase II transcribes a sequence on the DNA called POLYADENYLATION SIGNAL SEQUENCE that signals a polyadenylation sequence in the pre-RNA.

Then, proteins bind to it and cut free the mRNA free from RNA polymerase II

40
Q

polyadenylation sequence of the mRNA is:

A

AAUAAA

41
Q

termination (transcription) in prokaryotes

A
  1. transcription proceeds through a terminator sequence on the DNA
  2. The transcribed terminator serves as a signal causing RNA-polymerase to detach from DNA.
  3. The second step can be Rho-dependent or Rho-independent
42
Q

what is added in the 5’ end of the RNA?

A

methylated guanine

43
Q

functions of the 5’ capping?

A
  1. protects mRNA from ribonucleases in the cytoplasm
  2. recognises ribosomal units
  3. helps mRNA attach to the large subunit
44
Q

what is added in the 3’ end of the RNA?

A

poly (A) tail

45
Q

functions of the 3’ tailing?

A
  1. stabilizes mRNA
  2. interacts with proteins in the nuclear membrane to allow exit of mRNA from the nucleus
46
Q

which molecule does the splicing of pre-mRNA?

A

SPLICEOSOME

47
Q

what does spliceosome consist of?

A

snRNA and a large complex of proteins

48
Q

the nucleotide sequence of the tRNA where the aa binds?

A

CCA

49
Q

where does the specificity of a codon recognition lie?

A

in the tRNA, not the aa

50
Q

which enzyme catalyzes the attachment of the aa to the tRNA?

A

aminoacyl- tRNA synthetase

51
Q

aminoacylation

A

the process which attaches aa to the tRNA and requires ATP

52
Q

is base-pairing between tRNA and mRNA complementary?

A

no

53
Q

in which site does the first tRNA go?

A

the P site

54
Q

in which site does the first release factor bind to the STOP codon (RF1)?

A

the A site

55
Q

what does RF1 do to the peptide chain?

A

instead of an aa, it adds 1 molecule of water which breaks the bond between the tRNA in the P site and the completed polypeptide, which then leaves through the tunnel of the ribosomal large subunit.

56
Q

silent mutations

A

changes in the base of the codon, but the new codon still codes for the same aa

57
Q

missense mutations

A

changes in the base of the codon, which results in a different aa
may have little effect

58
Q

nonsense mutations

A

changes a normal codon to a STOP codon

59
Q

which enzymes cut bonds between aa?

A

proteases

60
Q

proteolysis

A

destruction of unfunctional proteins, carried out by PROTEASOMES

61
Q

where are proteasomes found?

A

in the nucleus and the cytosol

62
Q

promoter

A

a site where RNA-polymerase can bind to DNA and begin transcription

63
Q

Operator

A

on/off switch that controls whether RNA-polymerase has access to transcribe a gene or not

64
Q

repressor

A

a specific protein produced by a regulatory gene, which binds to the operator

65
Q

is the binding of the repressor to the operator reversible?

A

yes

66
Q

allosteric proteins

A

has 2 shapes, one active and one inactive

67
Q

what changes do histones undergo to make the genes accessible by enzymes?

A

acetylation- COCH3
methylation- CH3
phosphorylation- (PO3)2-

68
Q

are transcription factors general or specific?

A

there are two types
general and
specific

Biology (13 decks)

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