BLG1501
Assignment 2 Semester 2 2020
University of South Africa
;)
, Question 1[1]
1.1 The prompter of a gene includes the transcription starting point within it, the nucleotide
where RNA polymerase (the enzyme that unzips the double helix DNA strand into two
single DNA templates) begins the synthesis of mRNA and extends a few dozen
nucleotide pairs upstream from the start point. Based on its interactions with proteins,
RNA polymerase binds in a precise location and orientation to the promoter, and in turn
this determines where transcription starts and which of the two strands of the DNA
double helix will be used as the template. Certain sections of a promoter are especially
important for binding RNA polymerase in such a way that it ensures transcription starts
at the right place. In bacteria part of the polymerase self specifically recognises and
binds to the promoter. In eukaryotes, a collection of proteins called transcription factors
mediate the binding of RNA polymerase and the initiation of transcription. Only after
transcription factors are attached to the promoter does RNA polymerase II bind to it, this
process is called transcription initiation complex. A crucial promoter DNA sequence
TATA box forms the initiation complex at a eukaryotic promoter. The interaction between
eukaryotic RNA polymerase II and transcription factors shows the importance of protein-
protein interactions in controlling the eukaryotic transcription. Once appropriate
transcription factors are attached firmly to the promoter DNA and the polymerase is
bound to the DNA in the correct orientation, the polymerase unwinds the double helix
and starts the transcribing of the DNA template at the starting point. As the RNA
polymerase moves along the DNA, it uncoils the double helix, exposing 10-20 DNA
nucleotides at a time to pair with RNA nucleotides. As the RNA continues to move along
the template the enzyme adds nucleotides in 3’ to the end of the growing RNA molecule.
The new RNA molecule peels away from its DNA codon and the double helix of the DNA
reforms. The progress of transcription in eukaryotes are at a rate of about 40
nucleotides per second. One single gene can be transcribed by several molecules of
RNA polymerase following each other. An RNA strand which is growing, trails off from
each polymerase with the length of each new strand reflecting how far along the
template, the enzyme travelled from the start point. What helps to make the encoded
protein in large amounts, is the congregation of many polymerase molecules
simultaneously transcribing a single gene, which increases the amount of mRNA
transcribed from it. Eukaryotes and bacteria differ from each other in the way they
terminate transcription. In bacteria, transcription goes through a termination sequence in
the DNA. The transcribed terminator functions as the terminal signal, which causes the
polymerase to detach from the DNA and release the transcript, that requires no further
modification before translation. In eukaryotes the RNA polymerase II transcribes a
sequence on the DNA called the polyadenylation signal sequence, that specifies a
Assignment 2 Semester 2 2020
University of South Africa
;)
, Question 1[1]
1.1 The prompter of a gene includes the transcription starting point within it, the nucleotide
where RNA polymerase (the enzyme that unzips the double helix DNA strand into two
single DNA templates) begins the synthesis of mRNA and extends a few dozen
nucleotide pairs upstream from the start point. Based on its interactions with proteins,
RNA polymerase binds in a precise location and orientation to the promoter, and in turn
this determines where transcription starts and which of the two strands of the DNA
double helix will be used as the template. Certain sections of a promoter are especially
important for binding RNA polymerase in such a way that it ensures transcription starts
at the right place. In bacteria part of the polymerase self specifically recognises and
binds to the promoter. In eukaryotes, a collection of proteins called transcription factors
mediate the binding of RNA polymerase and the initiation of transcription. Only after
transcription factors are attached to the promoter does RNA polymerase II bind to it, this
process is called transcription initiation complex. A crucial promoter DNA sequence
TATA box forms the initiation complex at a eukaryotic promoter. The interaction between
eukaryotic RNA polymerase II and transcription factors shows the importance of protein-
protein interactions in controlling the eukaryotic transcription. Once appropriate
transcription factors are attached firmly to the promoter DNA and the polymerase is
bound to the DNA in the correct orientation, the polymerase unwinds the double helix
and starts the transcribing of the DNA template at the starting point. As the RNA
polymerase moves along the DNA, it uncoils the double helix, exposing 10-20 DNA
nucleotides at a time to pair with RNA nucleotides. As the RNA continues to move along
the template the enzyme adds nucleotides in 3’ to the end of the growing RNA molecule.
The new RNA molecule peels away from its DNA codon and the double helix of the DNA
reforms. The progress of transcription in eukaryotes are at a rate of about 40
nucleotides per second. One single gene can be transcribed by several molecules of
RNA polymerase following each other. An RNA strand which is growing, trails off from
each polymerase with the length of each new strand reflecting how far along the
template, the enzyme travelled from the start point. What helps to make the encoded
protein in large amounts, is the congregation of many polymerase molecules
simultaneously transcribing a single gene, which increases the amount of mRNA
transcribed from it. Eukaryotes and bacteria differ from each other in the way they
terminate transcription. In bacteria, transcription goes through a termination sequence in
the DNA. The transcribed terminator functions as the terminal signal, which causes the
polymerase to detach from the DNA and release the transcript, that requires no further
modification before translation. In eukaryotes the RNA polymerase II transcribes a
sequence on the DNA called the polyadenylation signal sequence, that specifies a
