Structure and function of nucleic
acids
Understand the structure and function of nucleic acids in order to
describe gene expression and the process of protein synthesis
Unit 11: Genetics and Genetic Engineering
P1/P2 – Structure and function of DNA and RNA
The structure and function of DNA
A nucleotide is a collection of nucleic acids. The two main types of nucleic acids
are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA is found and
replicated within the nucleus. The nucleus contains the nucleolus, and long
strings of chromatin where DNA is found. DNA stores the information needed to
make larger molecules called proteins. A nucleotide is composed of three types
of molecules, a phosphate group ( P 034 −¿ ), a pentose sugar and an organic or a
base that contains nitrogen, which are all linked together by condensation
reactions. DNA consists of two long strands of nucleotides that twist around each
other to form a ‘double helix’, a shape similar to a twisted ladder. The nitrogen-
containing base in a DNA nucleotide can be made up out of one of four different
types of molecules, Adenine (A), Guanine (G), Cytosine (C) and Thymine (T).
Adenine and Guanine are both double-ringed molecules known as purines.
Cytosine and Thymine are single-ringed molecules known as pyrimidines.
Pyrimidines are smaller than purines as they have a single ring structure while
purines have two rings. The bases pair up in a unique way, named
complementary base-pairing. The pairing rule determines which molecules pairs
with which. In this case, Adenine always pairs with Thymine and Cytosine always
pairs with Guanine. ‘Uprights’ hold the bases together vertically, and are made
up of two chains of phosphate and sugar molecules which alternate all the way
down the DNA molecules. These chains of sugar and phosphate molecules run
parallel to each other but in different directions, this gives them the name of
anti-parallel strands. ‘Rungs’ hold the paired molecules together, they are known
as organic bases. To make up the human body, cells have to produce more cells.
To do this, it must undergo cell division. This process causes each DNA molecule
in the parent cell to make a copy of itself so that each new cell can receive the
correct amount of DNA, the chromosomes of the new cells are then formed from
the DNA.
A Nucleotide
, DNA strand
DNA replication
The DNA molecule is shaped like a double helix, which is held together by
hydrogen bonds. During DNA replication, an enzyme called DNA helicase breaks
down the hydrogen bonds between the DNA strands. The DNA double helix
structure begins to uncoil into two separate strands. Sometimes the uncoiling
occurs in different regions, which creates ‘unzipped bubbles’. Each DNA strands
acts as a template for a new complementary strand to be made. After the
uncoiling, an enzyme called primase adds small sections of RNA nucleotides to
the DNA which are called primers. The primers act as a signal to start copying
the DNA. The primers are then later removed by an enzyme called exonuclease
acids
Understand the structure and function of nucleic acids in order to
describe gene expression and the process of protein synthesis
Unit 11: Genetics and Genetic Engineering
P1/P2 – Structure and function of DNA and RNA
The structure and function of DNA
A nucleotide is a collection of nucleic acids. The two main types of nucleic acids
are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA is found and
replicated within the nucleus. The nucleus contains the nucleolus, and long
strings of chromatin where DNA is found. DNA stores the information needed to
make larger molecules called proteins. A nucleotide is composed of three types
of molecules, a phosphate group ( P 034 −¿ ), a pentose sugar and an organic or a
base that contains nitrogen, which are all linked together by condensation
reactions. DNA consists of two long strands of nucleotides that twist around each
other to form a ‘double helix’, a shape similar to a twisted ladder. The nitrogen-
containing base in a DNA nucleotide can be made up out of one of four different
types of molecules, Adenine (A), Guanine (G), Cytosine (C) and Thymine (T).
Adenine and Guanine are both double-ringed molecules known as purines.
Cytosine and Thymine are single-ringed molecules known as pyrimidines.
Pyrimidines are smaller than purines as they have a single ring structure while
purines have two rings. The bases pair up in a unique way, named
complementary base-pairing. The pairing rule determines which molecules pairs
with which. In this case, Adenine always pairs with Thymine and Cytosine always
pairs with Guanine. ‘Uprights’ hold the bases together vertically, and are made
up of two chains of phosphate and sugar molecules which alternate all the way
down the DNA molecules. These chains of sugar and phosphate molecules run
parallel to each other but in different directions, this gives them the name of
anti-parallel strands. ‘Rungs’ hold the paired molecules together, they are known
as organic bases. To make up the human body, cells have to produce more cells.
To do this, it must undergo cell division. This process causes each DNA molecule
in the parent cell to make a copy of itself so that each new cell can receive the
correct amount of DNA, the chromosomes of the new cells are then formed from
the DNA.
A Nucleotide
, DNA strand
DNA replication
The DNA molecule is shaped like a double helix, which is held together by
hydrogen bonds. During DNA replication, an enzyme called DNA helicase breaks
down the hydrogen bonds between the DNA strands. The DNA double helix
structure begins to uncoil into two separate strands. Sometimes the uncoiling
occurs in different regions, which creates ‘unzipped bubbles’. Each DNA strands
acts as a template for a new complementary strand to be made. After the
uncoiling, an enzyme called primase adds small sections of RNA nucleotides to
the DNA which are called primers. The primers act as a signal to start copying
the DNA. The primers are then later removed by an enzyme called exonuclease
