Jan Das
Unit 11 – Genetics and Genetic Engineering
Assignment A – Structure and Function of Nucleic Acid
P1. The structure and function of DNA & RNA
DNA – Structure and function
The DNA or known as deoxyribonucleic acid, is a molecule that supplies the genetic
instructions that informs organisms on how to grow, survive and reproduce. Every cell has
DNA.
The DNA is made up of millions of nucleotides. These are molecules containing a
deoxyribose sugar, a phosphate and a base. These nucleotides are attached to each other
through phosphodiester bonds to create a ‘sugar-phosphate backbone’. The bond occurs
between the third carbon atom on the deoxyribose sugar of one nucleotide (known as the 3’)
and the fifth carbon atom on the sugar of the next nucleotide (known as the 5’).
Diagram of DNA:
There are two strands of DNA that run in opposite directions (antiparallel) to each other.
These strands are connected to each other along their entire lengths through the bases on
each nucleotide. The DNA consists of 4 different nitrogen bases: Cytosine (C), guanine (G),
adenine (A) and thymine (T). In a normal DNA strand, cytosine pairs with guanine and
adenine pairs with thymine. When these pairs are connected, they create a double helix
shape.
The replication of DNA
DNA replication is the process in which a cell creates its own identical copy of its DNA. This
process is carried out at the beginning of every cell division to ensure that each daughter cell
will inherit an identical copy/ duplicate of the DNA.
, Jan Das
● Initiation
This is the first stage of DNA replication. When the replication of DNA begins, it creates a
replication fork. The DNA helicase is found in the replication complex, where its responsible
for unwinding the double helix revealing the two strands so that they can be used as a
template for replication. It does this by the enzymes using ATP hydrolysis to break the bonds
between the nucleobases and separating the two strands by holding them together.
● Elongation
The second stage of the DNA replication. The DNA primase is another important enzyme for
DNA replication. The DNA primase is responsible for creating a short RNA primer that
initiates and starts the activity of DNA polymerase. Once the DNA polymerase has attached
to the two separated strands of DNA, it can start synthesise new DNA strands to match the
templates. DNA polymerase can only be able to extend/ elongate the primer by adding free
nucleotides to the 3’ end.
● Termination
The process of expanding the new DNA strands continues until there is either no more DNA
template strands left to replicate (i.e. at the end of the chromosome) or two replication forks
merge and stop the process. Once the replication/synthesis of DNA has finished, the newly
synthesised strands are bound and made stable. Two enzymes are needed for stabilising
the lagging strand, the RNAse H removes the RNA primer from the start of each Okazaki
fragment and then the DNA ligase joins the fragments together to form a one complete
strand.
RNA – Structure and function
The RNA known as the ribonucleic acid (similar to DNA) is a molecule that has nucleic acids
which is present in all living cells that functions to act as a messenger carrying genetic
instructions from converting DNA into proteins.
The RNA is made up of a monomeric unit called the nucleotides, which consist one out of
four types of a nitrogenous base, a ribose sugar molecule and a phosphate group. The RNA
is a single strand with nitrogenous bases which are adenine (A), guanine (G), cytosine (C)
and uracil (U).
Diagram of RNA:
Unit 11 – Genetics and Genetic Engineering
Assignment A – Structure and Function of Nucleic Acid
P1. The structure and function of DNA & RNA
DNA – Structure and function
The DNA or known as deoxyribonucleic acid, is a molecule that supplies the genetic
instructions that informs organisms on how to grow, survive and reproduce. Every cell has
DNA.
The DNA is made up of millions of nucleotides. These are molecules containing a
deoxyribose sugar, a phosphate and a base. These nucleotides are attached to each other
through phosphodiester bonds to create a ‘sugar-phosphate backbone’. The bond occurs
between the third carbon atom on the deoxyribose sugar of one nucleotide (known as the 3’)
and the fifth carbon atom on the sugar of the next nucleotide (known as the 5’).
Diagram of DNA:
There are two strands of DNA that run in opposite directions (antiparallel) to each other.
These strands are connected to each other along their entire lengths through the bases on
each nucleotide. The DNA consists of 4 different nitrogen bases: Cytosine (C), guanine (G),
adenine (A) and thymine (T). In a normal DNA strand, cytosine pairs with guanine and
adenine pairs with thymine. When these pairs are connected, they create a double helix
shape.
The replication of DNA
DNA replication is the process in which a cell creates its own identical copy of its DNA. This
process is carried out at the beginning of every cell division to ensure that each daughter cell
will inherit an identical copy/ duplicate of the DNA.
, Jan Das
● Initiation
This is the first stage of DNA replication. When the replication of DNA begins, it creates a
replication fork. The DNA helicase is found in the replication complex, where its responsible
for unwinding the double helix revealing the two strands so that they can be used as a
template for replication. It does this by the enzymes using ATP hydrolysis to break the bonds
between the nucleobases and separating the two strands by holding them together.
● Elongation
The second stage of the DNA replication. The DNA primase is another important enzyme for
DNA replication. The DNA primase is responsible for creating a short RNA primer that
initiates and starts the activity of DNA polymerase. Once the DNA polymerase has attached
to the two separated strands of DNA, it can start synthesise new DNA strands to match the
templates. DNA polymerase can only be able to extend/ elongate the primer by adding free
nucleotides to the 3’ end.
● Termination
The process of expanding the new DNA strands continues until there is either no more DNA
template strands left to replicate (i.e. at the end of the chromosome) or two replication forks
merge and stop the process. Once the replication/synthesis of DNA has finished, the newly
synthesised strands are bound and made stable. Two enzymes are needed for stabilising
the lagging strand, the RNAse H removes the RNA primer from the start of each Okazaki
fragment and then the DNA ligase joins the fragments together to form a one complete
strand.
RNA – Structure and function
The RNA known as the ribonucleic acid (similar to DNA) is a molecule that has nucleic acids
which is present in all living cells that functions to act as a messenger carrying genetic
instructions from converting DNA into proteins.
The RNA is made up of a monomeric unit called the nucleotides, which consist one out of
four types of a nitrogenous base, a ribose sugar molecule and a phosphate group. The RNA
is a single strand with nitrogenous bases which are adenine (A), guanine (G), cytosine (C)
and uracil (U).
Diagram of RNA:
