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Genetics > Chapter 13 > Flashcards

Chapter 13 Flashcards

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Biology 101 flashcards
1
Q

Toxin ⍺-Amanitin

A

is a potent inhibitor of RNA polymerase II

  • ⍺-Amanitin binds to RNA polymerase and jams the moving parts
    of the enzyme, interfering with its ability to move along DNA
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2
Q

The Primary
Structure of RNA

A

Single stranded

Ribose sugar

Has uracil rather than thymine

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3
Q

The Secondary Structure of RNA

A

forms by folding

connects by complementary regions

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4
Q

The structures of DNA and RNA compared:Composed of nucleotides

A

Y,N

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5
Q

The structures of DNA and RNA compared: Type of sugar

A

Deoxyribosoe, ribose

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6
Q

The structures of DNA and RNA compared: Presense of 2’OH

A

N,Y

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7
Q

The structures of DNA and RNA compared: Bases

A

A G C T
A G C U

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8
Q

The structures of DNA and RNA compared: Nucleotides joined by
phosphodiester bonds

A

Y,Y

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9
Q

The structures of DNA and RNA compared: Double or single stranded

A

d,s

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10
Q

The structures of DNA and RNA compared: secondary structure

A

double helix, many types

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11
Q

The structures of DNA and RNA compared: stability

A

stable, easily degraded

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12
Q

Ribosomal RNA: rRNA

A

– Make up the ribosome, the site of protein assembly

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13
Q

Messenger RNA: mRNA

A

– Carries coding instructions for a polypeptide chain from
DNA to a ribosome.

– After attaching to ribosome, an mRNA specifies the
sequence of the amino acids in a polypeptide chain and
provides a template.

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14
Q

pre-messenger RNAs
(pre-mRNAs)

A

– Large precursor molecules are the immediate products of transcription
in eukaryotic cells.

– Pre-mRNAs are modified before becoming mRNA and
exiting nucleus for translation into protein

Bacterial cells do not possess pre-mRNAs – in
these cells, transcription takes place concurrently
with translation.

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15
Q

Transfer RNA: tRNA

A

– Serves as the link between the coding sequence of
nucleotides in an mRNA molecule and the amino
acid sequence of a polypeptide chain.

– Each tRNA attaches to one particular type of amino
acid and helps incorporate that into the chain.

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16
Q

Small nuclear RNAs: snRNAs

A

– Found in the nuclei of eukaryotic cells
– Combine with small protein subunits to form small
nuclear ribonucleoproteins (snRNPs, ‘snurps’)
– Some participate in the processing of RNA, converting pre-mRNA into mRNA.

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17
Q

Small nucleolar RNAs: snoRNAs

A

–Take part in the processing of RNA

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18
Q

MicroRNAs: miRNAs

A

Very small and abundant RNA molecules found in the
cytoplasm of eukaryotic cells

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19
Q

– Small interfering RNAs: siRNAs

A

These carry out RNA interference (RNAi)

RNAi - process in which
small RNA molecules help
trigger the degradation of
mRNA or inhibit its translation
into protein.

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20
Q

Piwi-interacting RNAs: piRNAs

A
  • Found in mammalian testes
  • Similar to miRNAs and siRNAs
    – Role in suppressing the expression of transposable elements
    (DNA sequence that can change it’s position) in reproductive
    cells.
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21
Q

Long noncoding RNAS (IncRNAs)

A
  • Found in Eukaryotes
  • Relatively long RNA molecules
  • Provide a variety of functions, including
    regulation of gene expression
22
Q

CRISPR RNAs (crRNAs)

A
  • Assist in the destruction of foreign DNA molecules
  • Found in prokaryotic cells
23
Q

Transcription Is the Synthesis of an RNA
Molecule from a DNA template

A

Unlike DNA replication, where all nucleotides
are copied, only parts of the DNA molecule are
transcribed into RNA.

Transcription is a highly selective process:
individual genes are transcribed only as their products
are needed.

24
Q

Transcription requires three major components:

A
  1. A DNA template
  2. The raw materials (ribonucleotide
    triphosphates) to build a new RNA molecule.
  3. The transcription apparatus (consists of
    proteins necessary for catalyzing synthesis of
    RNA)
25
Q

Template strand (nucleotide strand used for transcription)
vs. Nontemplate strand (not usually transcribed)

A

Thus, within a gene, only one of the nucleotide strands is normally transcribed into RNA

26
Q

Transcription Unit –

A

stretch of DNA that
encodes an RNA molecule and the sequences
needed for its transcription.

Included within a transcription unit are three
critical regions:
* A promoter
* RNA-coding sequence
* Terminator

27
Q

Promoter

A

– DNA sequence that the transcription apparatus
recognizes and binds

28
Q

RNA-coding Sequence –

A

sequence of DNA nucleotides
that is copied into an RNA molecule

29
Q

Terminator

A

– sequence of nucleotides that signals where
transcription ends.

30
Q

The Transcription Apparatus

A

RNA polymerase carries out all the required steps for
transcription.

RNA polymerase actions are enhanced by a number
of accessory proteins that join and leave the
polymerase at different stages.

31
Q

Eukaryotic RNA Polymerases

A

Most Eukaryotic cells possess three distinct types of RNA
polymerase, each responsible for transcribing a different
class of RNA

RNA polymerase I – transcribes rRNA

RNA polymerase II – transcribes pre-mRNAs, snoRNAs,
some miRNAs, and some snRNAs

RNA polymerase III – transcribes other small RNA
molecules (tRNAs, small rRNAs, some miRNAs, and
some snRNAs

32
Q

Bacterial Transcription
Initiation

A

– transcription apparatus assembles on the
promoter and begins synthesis of RNA

33
Q

Bacterial Transcription
Elongation

A

– DNA is threaded through RNA polymerase
and the polymerase unwinds the DNA, adding new
nucleotides(to the 3’ end of the growing strand

34
Q

Bacterial Transcription
Termination

A

– recognition of the end of transcription and
separation of the RNA molecule from the DNA template

35
Q

Initiation comprises all necessary steps to
begin RNA synthesis:

A

1.Promoter recognition

2.Formation of a transcription bubble

3.Creation of the first bonds between rNTPs

4.Escape of the transcription apparatus from
the promoter

36
Q

Consensus sequences

A

sequences that possess
considerable similarity.

Consensus sequences usually imply an important function!

37
Q

Almost all bacterial promoters have –10 consensus
sequence (~10 bp upstream of the start site) sometimes
called the

A

Pribnow box:
– 5’ TATAAT 3’
– 3’ ATATTA 5’

Also common: –35 consensus sequence:
TTGACA

38
Q

Initiation

A

– Initial RNA synthesis: no primer is required.
– The location of the consensus sequence
determines the position of the start site.

39
Q

Elongation

A

– RNA elongation is carried out by RNA polymerase.
– RNA polymerase does have the ability to do some
backtracking and proofreading as well

40
Q

Termination

A

– Transcription stops after the terminator region
has been transcribed.

41
Q

There are two types of terminators:

A
  • Rho-dependent: requires
    an ancillary protein
    rho factor (⍴)
    It detaches due to helicase unzipping, want DNA and RNA to seperate
  • Rho-independent:: also
    referred to as intrinsic
    terminators, are able to
    cause termination
    without rho.
    Hairpin structure
    formed by inverted
    repeats, followed by a
    string of uracils
42
Q

Which of the following phrases does not
describe a function of the promoter?

A

Signals where transcription ends

43
Q

Eukaryotic Transcription and Bacterial
Transcription Differences

A

Eukaryotic cells possess three different RNA Polymerases
– Each recognizes a different promotor

  • Promoter recognition and initiation are also different!
    – Many accessory proteins take part in the binding of eukaryotic
    RNA polymerases to DNA templates
    – Different types of promoters require different proteins!
  • Chromatin structure in eukaryotes needs to be modified before
    transcription can begin. A more open configuration is required for
    the machinery access to begin transcription!
44
Q

Termination: The three RNA polymerases use different
mechanisms for termination

A

– RNA polymerase I: Requires a terminator factor similar to rho
factor (unlike rho, this termination factor binds to a DNA
sequence downstream of the terminator)
– RNA polymerase II: Does not occur at specific sequences
(will look at more detail in Ch. 14)
– RNA polymerase III: Ends transcription after transcribing a
terminator sequence that produces a string of uracil
nucleotides in the RNA molecule.
Recent research suggests that secondary structures
(hairpin, etc) are necessary

45
Q

Eukaryotic Transcription and Bacterial
Transcription Differences Initiation:

A

– Transcription in eukaryotes is initiated through the
assembly of the transcription machinery on the promoter

46
Q

Eukaryotic RNA Polymerases

A

Most Eukaryotic cells possess three distinct types of RNA
polymerase, each responsible for transcribing a different
class of RNA.

RNA polymerase I – transcribes rRNA

RNA polymerase II – transcribes pre-mRNAs, snoRNAs,
some miRNAs, and some snRNAs

RNA polymerase III – transcribes other small RNA
molecules (tRNAs, small rRNAs, some miRNAs, and
some snRNAs)

47
Q

Polymerase I and III Promoters

A

RNA polymerase I and RNA polymerase III each
recognize promoters that are distinct from those
recognized by RNA polymerase II.

Promoters for small rRNA and tRNA genes,
transcribed by RNA polymerase III, contain
internal promoters that are downstream of the
start site and are transcribed into the RNA

48
Q

Regulatory promoter

A

: located immediately upstream of the core
promoter.

Variety of different consensus sequences may be found in the
regulatory promoters.

49
Q

enhancers

A

Transcription activator proteins may also regulate transcription by
binding to more distant sequences

50
Q

Eukaryotic Promoters

A

Promoters recognized by RNA polymerase II – which transcribes
the genes that encode proteins.

– Core promoter is located immediately upstream of the gene,
(the site where basal transcription apparatus binds).

– TATA box TATAAAA – one of the most common promoter
sequences ( –25 to –30 bp), bound by transcription factors

51
Q

Transcriptional activator
proteins

A

– another class
of accessory proteins,
bind specific DNA
sequences and bring
about higher levels of
transcriptions by
stimulating assembly of
basal transcription
apparatus at the start site.

TATA box gets it started and box helps assemble apparatus

52
Q

One class of accessory
proteins comprises
general transcription
factors, which along with
RNA polymerase form the

A

basal transcription
apparatus

group of proteins that assemble near transcription start site
and initiates minimal
levels of transcription.

Genetics (19 decks)

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