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Biology 107 > LECTURE 21 > Flashcards

LECTURE 21 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Before RNA pol ll can bind to the DNA strand,

A

Several transcription factors midst bind to DNA first

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2
Q

Transcription initiation complex is made of

A

RNA pol ll and transcription factors

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3
Q

Promoter sequence specifies the

A

Orientation of RNA pol binding (which strand is the template and the direction of transcription)

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4
Q

Three stages of transcription

A

1) initiation
2) elongation
3) termination

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5
Q

Initiation

A

DNA strands unwind, polymerase initiates RNA synthesis at the start point

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6
Q

Elongation

A

RNA pol catalyzes formation of phophsodiester bonds to produce the RNA polymer

  • RNA pol moves down downstream making RNA transcript
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7
Q

Replication bubble is

A

A lot bigger and continues to grow

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8
Q

Transcription bubble

A

Stays the same size and closes up behind itself, does so with out additional enzymes

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9
Q

Termination

A

RNA transcript is released

  • RNA pol detaches from DNA
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10
Q

Ways for termination in bacteria. And what do they require

A

1) intrinsic
2) extrinsic
- requires a terminator sequence

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11
Q

Terminator sequence

A

sequence in the newly transcribed RNA that signals the end.

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12
Q

Intrinsic

A

Stem-loop forms because of GC-rich inverted repeat, this displaces RNA form template

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13
Q

Extrinsic

A

Uses a no step-loop terminator sequence, and requires a protein with helices activity, called rho, which binds to the transcript and, travelling faster then RNA pol, reaches the DNA/RNA duplex and unwinds it, RNA pol falls off.

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14
Q

Termination of transcription in eukaryotes

A

RNA pol ll transcribes a sequence in DNA called polydentalation signal sequence

  • signal sequence is recognized by proteins, cuts the mRNA. RNA pol keeps going
  • RNA exonucleonase eventually removes the trailing RNA and he,ps knock the polymerase off.

RNA pol l is terminated when a protein binds to DNA downstream of coding region, it knocks it off.

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15
Q

In both eukaryotes and prokaryotes, a single gene can be transcribed

A

Simultaneously by several molecules of RNA pol.

  • allows the cells to produce a lot of RNA in a short time.
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16
Q

In eukaryotes, RNA processing after transcription produces a mature

A

Messenger RNA (mature mRNA)

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17
Q

Post-transcriptional modifications

A

Are required to increase the stability of the transcript in the cytoplasm

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18
Q

In eukaryotes, there are THREE post-transcriptional modifications that occur to pre-mRNAs (in nucleus)

A

1) addition of a 5’ cap
2) addition of adenine nucleotides to 3’ end, making poly A-tail. The same enzyme that cut the RNA add the poly A-tail.
3) RNA splicing

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19
Q

Addition of 5’ cap

A

A modified form of a guanine is added to the 5’ end of the RNA polymer via an unusual 5’-5’ phosphate linkage.

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20
Q

addition of adenine nucleotides to 3’ end, making a

A

poly A-tail. The same enzyme that cut the RNA add the poly A-tail

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21
Q

5’ cap and poly-A tail important functions

A

1) facilitates the export of mRNA form nucleus
2) protected RNA form degration by exonucleases
3) helps ribosome attach to 5’ end of mRNA (in cytoplasm)

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22
Q

Introns

A

Large Portions of pre-mRNA are removed

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23
Q

Exons

A

Remaking sections after splicing are pasted together

24
Q

RNA splicing

A

Introns are removed and exons are pasted together.

25
Q

Almost all eukaryote genes have

A

Introns

26
Q

RNA splicing is sometimes carried out by

A

Spliceosomes

27
Q

Spliceoosomes consist of

A

Proteins and several small nuclear ribonucleoproteins (snRNPs) that recognize sites

28
Q

Steps for RNA splicing reaction

A

1 ). SnRNPs and other proteins form a complex = spliceosome

2 ). SnRNA base-pairs with nucleotides at specific sites along the intron.

3 ). The spliceosome cuts the RNA, releasing the intron for rapid degradation, and legatees the exons together

29
Q

Why do eukaryotes have introns?

A

1) some introns contain sequences that help regulate the expression of genes.
2) alternative splicing allows for an increase in diversity of proteins

30
Q

Alternative splicing

A

After transcription to produce many pre-mRNA molecules, each one could be spliced in a different way in the same nucleus, to produce a mixture of mRNAs that have different exons.

This way, the same gene could make 2 different proteins with different functions

31
Q

Is alternative splicing necessary

A

No

32
Q

Translation

A

The process by which the genetic code in mRNA directs the synthesis of proteins form amino acids

33
Q

TRNAs (transfer RNAs) are the adapter molecules that

A

Me diet the transfer of info from nuclei acids to proteins

34
Q

A specific amino acids acid is bonded to tRNA via

  • what’s the amino acid ?
A

Covalent bond

  • Phe
35
Q

tRNA contain multiple

A

Stems and loops due to complementary base pairing

36
Q

Because of hydrogen bonds, tRNA molecules

A

twists and folds into an L shape.

37
Q

The anticodon sequence in tRNA is

A

Complimentary and antiparallel to a codon in the mRNA

38
Q

The base pairing in tRNA gives

A

Specificity to translation

39
Q

Correct matching of tRNA and its associated amino acid is accomplished by

A

Aminoacytl-tRNA synthetases

40
Q

Linking amino acids to tRNA is _______. The reaction is couples to the

A

Endergonic Hydrolysis of ATP

41
Q

Proteins synthesis requires a steady supply of each of the 20 different charged tRNAs. How are they recharged ?

A

They get recharged by their own amino acetyl synthase after they transfer their amino acid to a growing peptide

42
Q

Ribosomes - enzymes of translation

A
  • facilitates the specific coupling of tRNA and mRNA codons during proteins synthesis
  • catalyses formation of peptide bonds
  • complexes made of proteins and rRNAs
43
Q

Ribosomes are made of two major subunits

A

1) large subunits (+ rRNAs)

2) small ribosomal subunit (+rRNA)

44
Q

S = Svedberg unit

A

Measures how fast something sediments (settles) in a liquid

45
Q

Streptomycin

A
  • binds to the small 16S rRNA is the 30S subunit of bacteria ribosome.

Interferes with translation in bacteria.

46
Q

Why doesn’t streptomycin effect eukaryotes

A

Has limited effect on translation of eukaryotes.

47
Q

High doses of streptomycin effects

A

Mitochondrial proteins synthesis

48
Q

Ribosomal large subunits has three binding sites for tRNA molecules:

A

1) A site (aminoacyl-tRNA binding site)
2) P site (peptideyl-tRNA binding site)
3) E site (exit site)

49
Q

A site (aminoacyl-tRNA binding site)

A

Aminoacytl tRNA enters here

50
Q

P site (peptideyl-tRNA binding site)

A

Holds the tRNA attached to the growing peptide chain

51
Q

E site (exit site)

A

Discharged tRNA leave the ribosomes form this site.

52
Q

The small subunits binds to the

A

mRNA

53
Q

Small subunits recognized the mRNA using its

A

rRNA to make initial complementary base pairing

54
Q

Shine-dalgarno sequence is located on

A

mRNA

55
Q

Shine-Dalgarno

A

This is recognized by the ribosome small subunit, using the 16S rRNA (S-D sequence is present in prokaryotes, not eukaryotes)

Biology 107 (21 decks)

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