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Genetics > Ch. 13 Transcription > Flashcards

Ch. 13 Transcription Flashcards

1
Q

where can DNA polymerases add dNTPs?

A

only add dNTPs to a free 3’ OH
5’ triphosphate –> 3’ OH on the 5 carbon sugar
a primer is needed to start DNA synthesis

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2
Q

what is the central dogma?

A

DNA (transcription) –> RNA (translation) –> protein

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3
Q

what are the building blocks for DNA?

A

dNTP

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4
Q

what are the building blocks for RNA?

A

NTP (ribonucleic triphosphates)

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5
Q

characteristics of RNA

A

(uracil)
less stable
have extra OH group on 2’ end of 5 carbon-sugar
no primer needed to start synthesis

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6
Q

how are NTPs added by RNA polymerases?

A

added to free 3’ OH

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7
Q

what are some characteristics of DNA replication?

A
  1. high fidelity (polymerases can “proofread” and only add correct nitrogenous base pairs)
  2. complete (entire genome replicated at each cell cycle)
  3. once and only once per cycle (avoid polyploidy)
  4. requires RNA primer to start (need 3’ OH)
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8
Q

characteristics of RNA transcription?

A
  1. somewhat faithful (proofreading present but some errors occur, not as impactful as errors in DNA because RNA is transient)
  2. NOT complete (only a subset of genes transcribed at one time)
  3. occurs predominantly in G1 and G2 phases
  4. no primer required to start
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9
Q

RNA structure

A
  1. ribose sugar
  2. thymine replaced by uracil
  3. primary structure is single stranded (more instability)
  4. can form double stranded secondary structures
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10
Q

what are hairpins/stem loops?

A

single strands of RNA tend to fold in on themselves to form base pairs to be more stable
-formed by hydrogen bonds

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11
Q

what is mRNA?

A

messenger RNA

  • found in nucleus and cytoplasm
  • carries genetic code for proteins
  • found in bacterial and eukaryotic cells
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12
Q

what is rRNA?

A

ribosomal RNA

  • found in the cytoplasm
  • structural and functional components of the ribosome
  • found in bacterial and eukaryotic cells
  • necessary for protein synthesis
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13
Q

what is tRNA?

A

transfer RNA

  • found in cytoplasm
  • helps incorporate amino acids into polypeptide chain
  • found in bacterial and eukaryotic cells
  • necessary for protein synthesis
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14
Q

define “gene”

A

any DNA sequence that is transcribed into an RNA molecule

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15
Q

RNA polymerase 1

A

transcribes:

large rRNAs

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16
Q

RNA polymerase 2

A

transcribes:
pre-mRNA
some snRNAs, snoRNAs, miRNAs

17
Q

what 3 components does transcription require?

A
  1. DNA template
  2. raw materials to build a new RNA molecule (NTPs)
  3. transcription apparatus (containing proteins to catalyze RNA synthesis)
18
Q

RNA is ____ and _____ to the template strand.

A

complementary

antiparallel

19
Q

what is the non template strand?

A

coding strand

20
Q

what is the most abundant type of RNA in our bodies?

A

80% of the cells RNA is ribosomal RNA! (rRNA)

21
Q

can you transcribe form either side of the double stranded DNA?

A

yes!
different RNAs can be transcribed by either side of the DNA (sometimes simultaneously) depending on what genes we wants to transcribe

22
Q

what is the transcriptional unit?

A

entire unit where transcription occurs
upstream (toward promoter)
downstream (toward terminator)
5’ –> 3’

23
Q

what is a promoter?

A

20-200bp
specify which polymerase is going to be used
initial binding site of RNA polymerase

(we do not transcribe the promoter, it is the STAGING GROUND, not the first site of actual transcription)

24
Q

what is the basal transcription apparatus?

A

basic unit that can transcribe

25
Q

what are transcription factors?

A

prepare for RNA polymerase to arrive, helps recruit polymerase to the promoter

26
Q

what is the core promoter?

A

place for RNA polymerase to bind initially, place where we assemble transcriptional apparatus

  • bound by basal transcription apparatus
  • immediately upstream of the gene to be transcribed
  • Catalyze synthesis of RNA**
27
Q

TATA box

A
  • regulatory sequence
  • involved in initiation of transcription
  • occurs 25-30 nucleotides upstream of the transcription start site
28
Q

3 phases of transcription?

A
  1. initiation (recruitment of polymerase to promoter)
  2. elongation (transcription, adding nucleotides)
  3. termination (ending transcription)
29
Q

what are the phases of transcription initiation?

A
  1. TF11D and TBD binds the TATA box and partially unwinds DNA
  2. TF11’S bind
  3. RNA Polymerase 2 is positioned over start site
  4. transcription bubble formed
  5. RNA Polymerase 2 starts transcribing
30
Q

TBP

A

TATA binding protein

-binds to TATA box

31
Q

TF11D

A

transcription factor for RNA polymerase 2

-binds to TATA box

32
Q

steps of elongation?

A

Transcriptions factors left behind

-RNA polymerase 2 moves along the DNA template

33
Q

steps of termination?

A
  1. RNA Polymerase 2 sometimes continues to transcribe past the end of a gene
  2. cleavage of pre-mRNA at a specific site occurs (cleavage site signals to stop)
  3. RAT1 (5’ to 3’ exonuclease) degrades extra RNA
  4. once RAT1 reaches RNA polymerase 2, transcription terminates
34
Q

what does exonuclease do?

A

degrades RNA from the outside

35
Q

what affect does DNA compaction into chromatin and histones have on transcription?

A

tightly packed DNA into chromaTin and histones limits accesS of RNA polymerase to DNA

36
Q

what do chromatin remodeling enzymes do?

A

can slide nucleosomes to increase accessibility of a promoter region to an RNA Polymerase 2

Genetics (21 decks)

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