Transcription Flashcards

(36 cards)

1
Q

Central Dogma (fundamental law

A

the mechanism whereby inherited
information is used to create “actual
objects”, namely enzymes and structural
proteins.

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2
Q

Prokaryotic genes are composed of three sequence regions

A

1.Promoter region
2.RNA coding sequence
3.Terminator region

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3
Q

The region 5’ of the promoter sequence is called

A

d upstream sequences

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4
Q

The region 3’ of the terminator sequence is called

A

downstream sequence

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5
Q

Transcription is

A

e first stage in gene
expression and the principal step at which
it is controlled.

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5
Q

RNA polymerase is characterized by:

A

▪Search DNA for initiation site,
▪It unwinds a short stretch of double helical DNA to produce a single stranded DNA template,
▪It selects the correct ribonucleotide
and catalyzes the formation of a
phosphodiester bond,
▪It detects termination signals where
transcript ends.

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6
Q

Transcription initiation

A

RNA polymerase binds to the DNA of the
gene at a region called the promoter

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7
Q

A promoter contains

A

DNA sequences that let RNA polymerase, or its helper proteins attach to the DNA.

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8
Q

Promoters in bacteria (initiation) contains two important DNA sequences

A

the -10 and -35 elements.

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9
Q

Promoters in eukaryotes (initiation)

A

helper proteins called basal (general)
transcription factors bind to the promoter first.

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10
Q

Many eukaryotic promoters have a sequence called a

A

TATA box (25-30 nucleotides)

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11
Q

Role of TATA box (25-30 nucleotides),

A

much like that of the -10 element in bacteria.

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12
Q

tata box also contains lots of As and Ts, which make it

A

easy to pull the strands of DNA apart

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13
Q

The eukaryotic cell contains three types of distinct RNA polymerases

A

(A) RNA polymerase Ι transcribe genes that yield rRNAs.
(B) RNA polymerase ΙΙ transcribes protein-coding genes and results in the synthesis of mRNAs.
(C) RNA polymerase ΙΙΙ transcribe genes that yield tRNAs.
All of these three are complex multi-subunits enzymes
consisting of 8-14 subunits each.

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14
Q

RNA polymerase (RNAP) directs the
sequential binding of ribonucleotides

A

to the growing RNA chain in the 5’ - 3’ direction.

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14
Q

During elongation, RNA polymerase “walks”
along one strand of DNA

A

known as the TEMPLATE STRAND, in the 3’ to 5’ direction.

14
Q

For each nucleotide in the template, RNA
polymerase

A

ADDS A MATCHING (complementary) RNA nucleotide to the 3’ end of the RNA strand.

15
Q

The RNA transcript is nearly identical to the
non-template, or coding, strand of DNA.
However,

A

RNA strands have the base uracil
(U) in place of thymine (T), as well as a
slightly different sugar in the nucleotide

16
Q

The process of ending transcription

A

is called termination

17
Q

Termination happens once

A

the polymerase transcribes a sequence of DNA known as terminator

18
Q

Terminators work in conjunction with RNA polymerase to

A

to loosen the association between RNA product and DNA template, so that RNA dissociate from RNA polymerase and DNA

19
Q

Termination in bacteria

A

Rho-dependent termination (Extrinsic),
Rho-independent termination (Intrinsic),

20
Q

In Rho-dependent termination (Extrinsic), the
RNA contains

A

a binding site for a protein called
Rho factor

21
Q

A hairpin slows down polymerase allowing a
trailing protein called rho

A

to catch up and DISLODGE the polymerase from the template.

22
Rho-independent termination, As the RNA polymerase approaches the end of the gene being transcribed
it hits a region RICH IN C and G nucleotides.
23
Termination in eukaryotes
Polyadenylation-dependent termination: Polyadenylation-independent termination
24
Polyadenylation-dependent termination: Begins when a
polyadenylation signal (AAUAAA) appears in the RNA transcript.
25
polyadenylation signal (AAUAAA)
is a sequence of nucleotides that marks where an RNA transcript should end
26
The polyadenylation signal is recognized by
an enzyme that cuts the RNA transcript nearby (Mostly occurring event
27
Polyadenylation-independent termination: The presence of specific termination sequences (RICH IN URACIL NUCEORTIDE)
is a hallmark of polyadenylation-independent termination.
28
recognition of these sequences by
RNA polymerase triggers the termination of transcription, leading to the release of the RNA transcript
29
Transcription is the
first step in gene expression
30
Transcription involves
copying a gene's DNA sequence to make an RNA molecule.
31
WHAT IS THE SIMILARITY BETWEEN TRANSCRIPTION & REPLICATION?
Similarities: transcription and replication both use DNA as the template for copying
32
WHAT IS A CRITICAL DIFFERENCE BETWEEN REPLICATION AND TRANSCRIPTION?
In transcription, a new molecule of mRNA is made from the template DNA by using the enzyme RNA polymerase. In DNA replication, a new molecule of DNA is made from the template DNA by using the enzyme DNA polymerase
33
**Transcription factors (TFs) are regulatory proteins whose function is to activate (or more rarely, to inhibit) transcription of DNA by binding to specific DNA sequences.