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Biology 230 > Chapter 7 > Flashcards

Chapter 7 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What do mRNAs code for?

A

proteins

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2
Q

RNAs that form the core of a ribosome

A

rRNAs

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3
Q

regulate gene expression

A

miRNAs

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4
Q

the process by which the information encoded in a DNA sequence is translated into a product that has some effect on a cell or organism

A

gene expression

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5
Q

start/stop sites of transcription

A

promoter / terminator

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6
Q

Is the promoter region transcribed? Terminator?

A

no / yes

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7
Q

RNA polymerase always moves in this direction

A

3’ ——> 5’

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8
Q

Initiation of transcription in bacteria:

A
  • sigma factor binds to promoter
  • RNA synthesis is initiated
  • sigma subunit dissociates
  • chain elongation continues until terminator sequence
  • RNA polymerase halts and releases the DNA and RNA transcript
  • polymerase reassociates with the sigma factor
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9
Q

accessory proteins in eukaryotes that assemble on the promoter where they position the RNA polymerase and pull apart the DNA double helix, allowing RNA polymerase to begin transcription

A

general transcription factors

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10
Q

How the transcription factors assemble:

A
  1. ) TFIID binds to TATA box causing a distortion in the DNA
  2. ) TFIID enables the binding of TFIIB
  3. ) more transcription factors and RNA polymerase II bind
  4. ) TFIIH uses ATP to pull apart DNA at the transcription start site
  5. ) TFIIH also phosphorylates RNA polymerase II
  6. ) RNA polymerase is released from complex
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11
Q

post-transcription professing

A

5’ cap
poly A tail
splicing

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12
Q

Is the poly A tail transcribed?

A

no

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13
Q

Purposes of modifications after transcription:

A
  • marks transcript as mRNA
  • facilitates exports to cytoplasm
  • increases stability of mRNA
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14
Q

Where does post-transcription modifications occur?

A

nucleus

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15
Q

DMD gene (dystrophin)

A
  • 78 introns
  • occupies 2,000,000 base pairs on chromosome X
  • mRNA is 14,00 nucleotides long
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16
Q

process of removing introns and stitching exons together

A

RNA splicing

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17
Q

When does splicing occur?

A

after capping

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18
Q

What structure does the intron form when it is cut out?

A

lariat structure

19
Q

How does the lariat structure form?

A
  1. ) branch point adenine in the intron sequence attacks the 5’ splice site and cuts the sugar-phosphate backbone of the RNA
  2. ) the cut 5’ end of the intron becomes covalently linked to the 2’-OH group of the ribose of the A nucleotide
  3. ) the free 3’-OH end of the exon sequence reacts with the start of the next exon sequence, joining the two together
20
Q

carries out RNA splicing

A

snRNAs

21
Q

snRNAs are packaged with proteins to form?

A

snRNPs (U1, U2, U4, U5, U6)

22
Q

the large assembly of RNA and protein molecules that carries out RNA splicing in the nucleus

A

spliceosome

23
Q

form the core of the spliceosome

A

snRNPs

24
Q

mediate the transport of RNA out of the nucleus

A

nuclear pore complexes

25
Q

mRNA lifetime is longer in eukaryotes or prokaryotes?

A

eukaryotes

26
Q

serves as an adaptor that “reads” a codon in mRNA and adds the correct amino acid to the growing polypeptide chain

A

tRNA

27
Q

a set of three consecutive nucleotides that bind to the complementary codon in an mRNA molecule

A

anticodon

28
Q

What does wobble mean?

A

some tRNAs require base-pairing only at the first two positions of the codon and can tolerate a mismatch at the third position

29
Q

covalently couple each amino acid to it’s appropriate set of tRNA molecules

A

aminoacyl-tRNA synthetases

30
Q

What is the large subunit of a ribosome composed of?

A

small proteins and rRNAs

31
Q

function of large subunit? small subunit?

A
  • large subunit— catalyzes peptide binds

* small subunit— matches mRNA codons to tRNAs

32
Q

RNA molecules that posses catalytic activity

A

ribozymes

33
Q

start and stop sites of translation

A 
start codon (AUG) 
stop codon (UGA, UAG, UAA)
34
Q

always carries that amino acid Met

A

initiator tRNA

35
Q

mRNA that codes for several different proteins, each of which is translated from the same mRNA molecule (only in prokaryotes)

A

polycistronic

36
Q

Do stop codons code for an amino acid?

A

no

37
Q

What stops translation?

A

release factor enters A site, peptidyl transferase catalyzes the addition of water instead of an amino acid, polypeptide chain is released

38
Q

many ribosomes working simultaneously on a single mRNA molecule

A

polyribosomes

39
Q

specialized pathways that break down proteins

A

proteolysis

40
Q

the enzyme that degrades proteins

A

professes

41
Q

large proteins machines in eukaryotes that break down proteins

A

proteasomes

42
Q

Where are proteasomes found?

A

cytosol and nucleus

43
Q

How do proteasomes select which proteins should be degraded?

A

proteins marked with ubiquitin

44
Q

Post-translational modifications:

A
  • covalent modifications (phosphorylation)
  • the binding of small-molecule cofactors
  • association with other protein subunits

Biology 230 (2 decks)

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