Abdur Rahman Benrezzouk
Unit 11 genetic engineering
Task 1
What is the structure of the nucleotide?
Nucleic acids are found in all living organisms whether they are eukaryotic or prokaryotic
cells or akaryotes (eg viruses). Nucleic acids can be DNA (deoxyribonucleic acid) or RNA
(ribonucleic acid) and both of these are polymers made up of single monomer units called
nucleotides.
A nucleotide is made up of three components
i. The phosphate group,
ii. The pentose sugar.
Iii. Base - there are 5 nitrogenous bases to be considered, which are adenine (A), thymine
(T), guanine (G) or cytosine (C). This is true of any DNA strand however, RNA nucleotides
differ in that they don’t contain a thymine base instead they have a uracil base (U).
The phosphate group in a nucleotide is joined to the pentose sugar. There are two types of
pentose sugar. Pentose sugars found in DNA are known as deoxyribose and the pentose
sugars in RNA are known as ribose sugars.
There are 5 different type of bases split into two groups, one group called purines have
bases named adenine and guanine and the other group called pyrimidines which include
thymine, uracil, and cytosine. Purines complementary base pair with pyrimidines depending
on whether complementary base pairing is happening in the DNA strand or mRNA strand.
Hence adenine pairs with thymine if it’s a DNA strand but will pair with uracil if it’s a mRNA
strand whereas cytosine always pairs with guanine whether it’s a DNA strand or mRNA
stand.
In addition to being building blocks for the construction of nucleic acid polymers called
polynucleotides, singular nucleotides play roles in cellular energy stores and provision,
cellular signalling, as a source of phosphate groups used to modulate the activity of proteins
and other signalling molecules, and as enzymatic cofactors.
Main features of DNA and DNA replication
The main features of DNA is that it contains two polymer chains of nucleotides that have
been joined together and twisted much like a ladder that has been twisted. The sides of the
ladder being the phosphate and sugar groups with the rungs of the ladder being the
complementary base pairs. The two backbone chains of deoxyribose sugars and phosphate
, Abdur Rahman Benrezzouk
groups are arranged in the double helix in an anti parallel fashion, in that each strand runs in
opposite directions. The complementary base paired bases (A-T, C-G) from each strand are
joined together by hydrogen bonds.
DNA Replication
DNA replication is the process whereby DNA produces identical copies of itself in order to
allow cell division to take place and pass on a copy of the genetic information. Before a cell
divides it needs to make copies of the DNA it holds in the nucleus and this happens during a
part of the cell cycle which is known as the S phase of interphase.
Interphase is the phase of the cell cycle that most cells spend their time in because they
synthesis vital molcules, grow and where the cell organelles and DNA replicate before
mitotic cell division occurs
This is done by the DNA strand completely unwinding bit by bit, breaking the hydrogen
bonds holding the bases of both strands together. In order for this to happen the enzyme
helicase attaches to the strand and breaks apart the hydrogen bonds which are keeping the
double helix DNA strand intact, once this strand has been broken apart the DNA will unravel
and separate into two strands.
This leaves two strands of exposed bases which act as a template for free nucleotides to
come and complementary base pair with the exposed bases on the original DNA strand. So
base A complementary base pairs wiyh base T and C- to G.
The above process is catalysed by DNA polymerase enzymes. The DNA polymerase will
make its way down the unwound DNA and prompt floating nucleotides in the nucleoplasm
of the nucleus to create the new strand by complementary base pairing. The nucleotides
that have base paired are zipped up by covalent bonds forming between the sugar group of
one nucleotide and the phosphate group of its neighbouring nucleotide. This zipping up of
the newly attached nucleotides to form a polynucleotide strand is catalysed by the enzyme
ligase.
By the end of the DNA replication process there will be two identical molecules of DNA that
are identical to the original or parent molecule of DNA but in each molecule one strand
comes from the parent DNA whereas the other strand is composed of the newly created
one and for this reason this form of replication is known as semi conservative replication.
Unit 11 genetic engineering
Task 1
What is the structure of the nucleotide?
Nucleic acids are found in all living organisms whether they are eukaryotic or prokaryotic
cells or akaryotes (eg viruses). Nucleic acids can be DNA (deoxyribonucleic acid) or RNA
(ribonucleic acid) and both of these are polymers made up of single monomer units called
nucleotides.
A nucleotide is made up of three components
i. The phosphate group,
ii. The pentose sugar.
Iii. Base - there are 5 nitrogenous bases to be considered, which are adenine (A), thymine
(T), guanine (G) or cytosine (C). This is true of any DNA strand however, RNA nucleotides
differ in that they don’t contain a thymine base instead they have a uracil base (U).
The phosphate group in a nucleotide is joined to the pentose sugar. There are two types of
pentose sugar. Pentose sugars found in DNA are known as deoxyribose and the pentose
sugars in RNA are known as ribose sugars.
There are 5 different type of bases split into two groups, one group called purines have
bases named adenine and guanine and the other group called pyrimidines which include
thymine, uracil, and cytosine. Purines complementary base pair with pyrimidines depending
on whether complementary base pairing is happening in the DNA strand or mRNA strand.
Hence adenine pairs with thymine if it’s a DNA strand but will pair with uracil if it’s a mRNA
strand whereas cytosine always pairs with guanine whether it’s a DNA strand or mRNA
stand.
In addition to being building blocks for the construction of nucleic acid polymers called
polynucleotides, singular nucleotides play roles in cellular energy stores and provision,
cellular signalling, as a source of phosphate groups used to modulate the activity of proteins
and other signalling molecules, and as enzymatic cofactors.
Main features of DNA and DNA replication
The main features of DNA is that it contains two polymer chains of nucleotides that have
been joined together and twisted much like a ladder that has been twisted. The sides of the
ladder being the phosphate and sugar groups with the rungs of the ladder being the
complementary base pairs. The two backbone chains of deoxyribose sugars and phosphate
, Abdur Rahman Benrezzouk
groups are arranged in the double helix in an anti parallel fashion, in that each strand runs in
opposite directions. The complementary base paired bases (A-T, C-G) from each strand are
joined together by hydrogen bonds.
DNA Replication
DNA replication is the process whereby DNA produces identical copies of itself in order to
allow cell division to take place and pass on a copy of the genetic information. Before a cell
divides it needs to make copies of the DNA it holds in the nucleus and this happens during a
part of the cell cycle which is known as the S phase of interphase.
Interphase is the phase of the cell cycle that most cells spend their time in because they
synthesis vital molcules, grow and where the cell organelles and DNA replicate before
mitotic cell division occurs
This is done by the DNA strand completely unwinding bit by bit, breaking the hydrogen
bonds holding the bases of both strands together. In order for this to happen the enzyme
helicase attaches to the strand and breaks apart the hydrogen bonds which are keeping the
double helix DNA strand intact, once this strand has been broken apart the DNA will unravel
and separate into two strands.
This leaves two strands of exposed bases which act as a template for free nucleotides to
come and complementary base pair with the exposed bases on the original DNA strand. So
base A complementary base pairs wiyh base T and C- to G.
The above process is catalysed by DNA polymerase enzymes. The DNA polymerase will
make its way down the unwound DNA and prompt floating nucleotides in the nucleoplasm
of the nucleus to create the new strand by complementary base pairing. The nucleotides
that have base paired are zipped up by covalent bonds forming between the sugar group of
one nucleotide and the phosphate group of its neighbouring nucleotide. This zipping up of
the newly attached nucleotides to form a polynucleotide strand is catalysed by the enzyme
ligase.
By the end of the DNA replication process there will be two identical molecules of DNA that
are identical to the original or parent molecule of DNA but in each molecule one strand
comes from the parent DNA whereas the other strand is composed of the newly created
one and for this reason this form of replication is known as semi conservative replication.
