MS 20454151
Structure and function of nucleic acids
DNA
DNA (deoxyribonucleic acid) is a molecule
containing the genetic code of every living
organism. It is responsible for storing and
replicating genetic information. DNA is stored as
chromosomes in the nucleus of cells. DNA is
made up of two strands called polynucleotide
chains, that form into a double helix
resembling a twisted ladder. DNA is a polymer
composed of nucleotides, and each nucleotide
contains phosphates, deoxyribose sugar
(these form the two vertical strands) and a
nitrogenous base. These nucleotide bases
include, Adenine (A), Cytosine (C), Guanine (G), Thymine (T). Adenine
and thymine always pair with each other, as do cytosine and guanine.
These base pairs contain a hydrogen bond which holds the
polynucleotide units together. Human DNA consists of around 3 billion
bases. DNA has an important property of duplicating itself and the
structure of DNA allows this to be done easily. Each strand in the double
helix can be used as a template for the duplicating the sequence of base
pairs. The sequence of bases determines the genetic code created by the
genome.
RNA
RNA (ribonucleic acid) is a molecule that is present in every living
organism, and it can be found in the nucleolus. It has many functions such
as helping with protein synthesis, carrying genetic information, behaving
as a catalyst in biochemical reactions etc. Structurally, RNA is relatively
similar to DNA the only difference being that it has one strand instead of
two and it contains only one ribose sugar molecule. RNA is made up of the
same nitrogenous bases in DNA excluding Thymine which is replaced by
Uracil. This means that the base pairs are the same as DNA however
adenine pairs with Uracil instead of thymine. RNA is shorter than DNA as it
is taken from a specific section of the DNA. There are various types of
RNA, the main three being mRNA, rRNA and tRNA.
Page 1 | 9
, MS 20454151
Messenger RNA (mRNA): Messenger RNA copies genetic material
through a process called transcription before transferring the genetic
material into ribosomes where protein synthesis takes place. Protein
synthesis facilitates from the code given by the messenger RNA.
Messenger RNA is a single stranded linear molecule composed of
nucleotides.
Transfer RNA (tRNA): transfer RNA is responsible for selecting the
correct amino acids (building blocks for protein) and transporting them to
protein factories (ribosomes). This is a direct response to the coded
instructions previously given by the messenger RNA. This process is called
translation. Transfer RNA is single stranded and has L shaped cloverleaf
shape.
Ribosomal RNA (rRNA): Ribosomal RNA is a component of ribosomes
that plays a vital role in protein production. Ribosomal RNA has a complex
three-dimensional structure split into the large subunit (LSU) and the
small subunit(SSU).
DNA Replication
DNA replication is the process in which the DNA creates multiple copies of
itself. DNA replication is one of the most basic processes that takes place
within a cell, and it is important so that the replicated cells (daughter
cells) that come out of it contain the exact same genetic information as
the parent cell. DNA replication occurs in three major steps: initiation,
elongation and termination.
Initiation: the initiation occurs in two steps. Firstly, an initiator protein will
target origin points within the DNA strand, and it begins unwinding the
DNA double helix. This is then followed by an enzyme known as DNA
helicase attaching to and breaking the hydrogen bonds holding the DNA
strands together further unwinding the two strands. This needs to happen
so that the DNA strands can be used as templates. The separation of the
Page 2 | 9
Structure and function of nucleic acids
DNA
DNA (deoxyribonucleic acid) is a molecule
containing the genetic code of every living
organism. It is responsible for storing and
replicating genetic information. DNA is stored as
chromosomes in the nucleus of cells. DNA is
made up of two strands called polynucleotide
chains, that form into a double helix
resembling a twisted ladder. DNA is a polymer
composed of nucleotides, and each nucleotide
contains phosphates, deoxyribose sugar
(these form the two vertical strands) and a
nitrogenous base. These nucleotide bases
include, Adenine (A), Cytosine (C), Guanine (G), Thymine (T). Adenine
and thymine always pair with each other, as do cytosine and guanine.
These base pairs contain a hydrogen bond which holds the
polynucleotide units together. Human DNA consists of around 3 billion
bases. DNA has an important property of duplicating itself and the
structure of DNA allows this to be done easily. Each strand in the double
helix can be used as a template for the duplicating the sequence of base
pairs. The sequence of bases determines the genetic code created by the
genome.
RNA
RNA (ribonucleic acid) is a molecule that is present in every living
organism, and it can be found in the nucleolus. It has many functions such
as helping with protein synthesis, carrying genetic information, behaving
as a catalyst in biochemical reactions etc. Structurally, RNA is relatively
similar to DNA the only difference being that it has one strand instead of
two and it contains only one ribose sugar molecule. RNA is made up of the
same nitrogenous bases in DNA excluding Thymine which is replaced by
Uracil. This means that the base pairs are the same as DNA however
adenine pairs with Uracil instead of thymine. RNA is shorter than DNA as it
is taken from a specific section of the DNA. There are various types of
RNA, the main three being mRNA, rRNA and tRNA.
Page 1 | 9
, MS 20454151
Messenger RNA (mRNA): Messenger RNA copies genetic material
through a process called transcription before transferring the genetic
material into ribosomes where protein synthesis takes place. Protein
synthesis facilitates from the code given by the messenger RNA.
Messenger RNA is a single stranded linear molecule composed of
nucleotides.
Transfer RNA (tRNA): transfer RNA is responsible for selecting the
correct amino acids (building blocks for protein) and transporting them to
protein factories (ribosomes). This is a direct response to the coded
instructions previously given by the messenger RNA. This process is called
translation. Transfer RNA is single stranded and has L shaped cloverleaf
shape.
Ribosomal RNA (rRNA): Ribosomal RNA is a component of ribosomes
that plays a vital role in protein production. Ribosomal RNA has a complex
three-dimensional structure split into the large subunit (LSU) and the
small subunit(SSU).
DNA Replication
DNA replication is the process in which the DNA creates multiple copies of
itself. DNA replication is one of the most basic processes that takes place
within a cell, and it is important so that the replicated cells (daughter
cells) that come out of it contain the exact same genetic information as
the parent cell. DNA replication occurs in three major steps: initiation,
elongation and termination.
Initiation: the initiation occurs in two steps. Firstly, an initiator protein will
target origin points within the DNA strand, and it begins unwinding the
DNA double helix. This is then followed by an enzyme known as DNA
helicase attaching to and breaking the hydrogen bonds holding the DNA
strands together further unwinding the two strands. This needs to happen
so that the DNA strands can be used as templates. The separation of the
Page 2 | 9
