Unit 11: Genetic and genetic engineering
Iesa Majeed February 2022
STRUCTURE AND FUNCTION OF NUCLEIC ACIDS
Deoxyribonucleic Acid
Deoxyribonucleic acid, also known as DNA, is a basic molecule of life present in
every living organism from humans to plants. It was discovered in 1953 by Dr
Watson and Dr Crick. Its main function is to carry unique genetic code that every
living organism needs for living, developing, and reproducing. DNA carries
information form parent to child.
DNA molecules are exceptionally long and cannot fit if they do not have the right
“packing”. DNA form chromosomes by coiling tightly. Every chromosome has a
single DNA molecule. Humans usually have 23 pairs of chromosomes. These are
composed of two polynucleotide chains that are twisted and take the shape of a
double helix. Each nucleotide found in the chain is made by a pentose (5 carbon)
sugar, a nitrogen organic base and a phosphate group.
As mentioned before, we know that DNA has two main functions. First is replication;
every time a cell divides DNA its genes must be copied to make another DNA
molecule. Its other function is “characteristics”. The genes encode through the
proteins they code for. Within a cell’s nucleus it holds the genome, this is split in 23
pairs of chromosomes. Each chromosome holds long strands of unique DNA which
is wrapped around a protein called histones.
The DNA molecule is too big and unable to leave the nucleus. Therefore, the DNA
sends a messenger that carries all information needed. As the DNA is two stranded
only one strand holds the codons that hold the information for the amnio acids, this
strand runs 5’ to 3’. It is named the sense strand or coding strand because of its
function. As DNA strands are anti-parallel which means one strand runs 3’ to 5’, thus
being the antisense strand.
,Diagram Primary structure of DNA.
Every element of the nucleotides has a significant role
Pentose sugar
This is a five numbered ring of four carbon atoms and one oxygen atoms. The base
is attached to carbon 1, carbon 2 and has a hydrogen attached. This is called a
deoxyribose. The carbon 3 and the nucleotides attached in a single direction and the
carbon 5 has a phosphate group attached.
Phosphate group
This is essential for the backbone structure of DNA. This group is the reason both
DNA and RNA are negatively charged.
, Nitrogen Organic Bases
There are two types of organic bases, these are pyrimidine and purine. The
pyrimidines have a single ring structure that includes Cytosine (C) and Thymine (T).
Purine has a double ring structure which are Adenine (A) and Guanine (G). The base
pairing in DNA is specific, Adenine always pairs with thymine and cytosine always
pairs with guanine.
Diagram DNA structure bonds
Iesa Majeed February 2022
STRUCTURE AND FUNCTION OF NUCLEIC ACIDS
Deoxyribonucleic Acid
Deoxyribonucleic acid, also known as DNA, is a basic molecule of life present in
every living organism from humans to plants. It was discovered in 1953 by Dr
Watson and Dr Crick. Its main function is to carry unique genetic code that every
living organism needs for living, developing, and reproducing. DNA carries
information form parent to child.
DNA molecules are exceptionally long and cannot fit if they do not have the right
“packing”. DNA form chromosomes by coiling tightly. Every chromosome has a
single DNA molecule. Humans usually have 23 pairs of chromosomes. These are
composed of two polynucleotide chains that are twisted and take the shape of a
double helix. Each nucleotide found in the chain is made by a pentose (5 carbon)
sugar, a nitrogen organic base and a phosphate group.
As mentioned before, we know that DNA has two main functions. First is replication;
every time a cell divides DNA its genes must be copied to make another DNA
molecule. Its other function is “characteristics”. The genes encode through the
proteins they code for. Within a cell’s nucleus it holds the genome, this is split in 23
pairs of chromosomes. Each chromosome holds long strands of unique DNA which
is wrapped around a protein called histones.
The DNA molecule is too big and unable to leave the nucleus. Therefore, the DNA
sends a messenger that carries all information needed. As the DNA is two stranded
only one strand holds the codons that hold the information for the amnio acids, this
strand runs 5’ to 3’. It is named the sense strand or coding strand because of its
function. As DNA strands are anti-parallel which means one strand runs 3’ to 5’, thus
being the antisense strand.
,Diagram Primary structure of DNA.
Every element of the nucleotides has a significant role
Pentose sugar
This is a five numbered ring of four carbon atoms and one oxygen atoms. The base
is attached to carbon 1, carbon 2 and has a hydrogen attached. This is called a
deoxyribose. The carbon 3 and the nucleotides attached in a single direction and the
carbon 5 has a phosphate group attached.
Phosphate group
This is essential for the backbone structure of DNA. This group is the reason both
DNA and RNA are negatively charged.
, Nitrogen Organic Bases
There are two types of organic bases, these are pyrimidine and purine. The
pyrimidines have a single ring structure that includes Cytosine (C) and Thymine (T).
Purine has a double ring structure which are Adenine (A) and Guanine (G). The base
pairing in DNA is specific, Adenine always pairs with thymine and cytosine always
pairs with guanine.
Diagram DNA structure bonds
