Transcription Flashcards

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
Q

Rho-independent termination, As the RNA polymerase approaches the end of the gene being transcribed

A

it hits a region RICH IN C and G nucleotides.

23
Q

Termination in eukaryotes

A

Polyadenylation-dependent termination:
Polyadenylation-independent termination

24
Q

Polyadenylation-dependent termination: Begins when a

A

polyadenylation signal (AAUAAA) appears in the RNA transcript.

25
Q

polyadenylation signal (AAUAAA)

A

is a sequence of nucleotides that marks where an RNA transcript should end

26
Q

The polyadenylation signal is recognized by

A

an enzyme that cuts the RNA transcript nearby (Mostly occurring event

27
Q

Polyadenylation-independent termination: The presence of specific termination sequences (RICH IN URACIL NUCEORTIDE)

A

is a hallmark of polyadenylation-independent termination.

28
Q

recognition of these sequences by

A

RNA polymerase triggers the termination of transcription, leading to the release of the RNA transcript

29
Q

Transcription is the

A

first step in gene expression

30
Q

Transcription involves

A

copying a gene’s DNA sequence to make an RNA molecule.

31
Q

WHAT IS THE SIMILARITY BETWEEN TRANSCRIPTION & REPLICATION?

A

Similarities: transcription and replication both use DNA as the template for copying

32
Q

WHAT IS A CRITICAL DIFFERENCE BETWEEN REPLICATION AND TRANSCRIPTION?

A

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
Q

**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.

A