Transcription

Question 1

Central Dogma (fundamental law

Answer 1

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

Question 2

Prokaryotic genes are composed of three sequence regions

Answer 2

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

Question 3

The region 5’ of the promoter sequence is called

Answer 3

d upstream sequences

Question 4

The region 3’ of the terminator sequence is called

Answer 4

downstream sequence

Question 5

Transcription is

Answer 5

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

Question 5

RNA polymerase is characterized by:

Answer 5

▪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.

Question 6

Transcription initiation

Answer 6

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

Question 7

A promoter contains

Answer 7

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

Question 8

Promoters in bacteria (initiation) contains two important DNA sequences

Answer 8

the -10 and -35 elements.

Question 9

Promoters in eukaryotes (initiation)

Answer 9

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

Question 10

Many eukaryotic promoters have a sequence called a

Answer 10

TATA box (25-30 nucleotides)

Question 11

Role of TATA box (25-30 nucleotides),

Answer 11

much like that of the -10 element in bacteria.

Question 12

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

Answer 12

easy to pull the strands of DNA apart

Question 13

The eukaryotic cell contains three types of distinct RNA polymerases

Answer 13

(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.

Question 14

RNA polymerase (RNAP) directs the
sequential binding of ribonucleotides

Answer 14

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

Question 14

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

Answer 14

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

Question 14

For each nucleotide in the template, RNA
polymerase

Answer 14

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

Question 15

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

Answer 15

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

Question 16

The process of ending transcription

Answer 16

is called termination

Question 17

Termination happens once

Answer 17

the polymerase transcribes a sequence of DNA known as terminator

Question 18

Terminators work in conjunction with RNA polymerase to

Answer 18

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

Question 19

Termination in bacteria

Answer 19

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

Question 20

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

Answer 20

a binding site for a protein called
Rho factor

Question 21

A hairpin slows down polymerase allowing a
trailing protein called rho

Answer 21

to catch up and DISLODGE the polymerase from the template.

Question 22

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

Answer 22

it hits a region RICH IN C and G nucleotides.

Question 23

Termination in eukaryotes

Answer 23

Polyadenylation-dependent termination:
Polyadenylation-independent termination

Question 24

Polyadenylation-dependent termination: Begins when a

Answer 24

polyadenylation signal (AAUAAA) appears in the RNA transcript.

Question 25

polyadenylation signal (AAUAAA)

Answer 25

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

Question 26

The polyadenylation signal is recognized by

Answer 26

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

Question 27

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

Answer 27

is a hallmark of polyadenylation-independent termination.

Question 28

recognition of these sequences by

Answer 28

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

Question 29

Transcription is the

Answer 29

first step in gene expression

Question 30

Transcription involves

Answer 30

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

Question 31

WHAT IS THE SIMILARITY BETWEEN TRANSCRIPTION & REPLICATION?

Answer 31

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

Question 32

WHAT IS A CRITICAL DIFFERENCE BETWEEN REPLICATION AND TRANSCRIPTION?

Answer 32

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

Question 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.