S012617 : Joshua Sharp
Unit 13 : A
DNA Replication and the Impact of Variation in
the DNA Sequence
Structure of DNA
DNA is a polymer comprised of two strands of genetic information in a
structure known as the double helix. Each respective strand is comprised
of a chain of nucleotides. In each nucleotide, there is three respective key
components, the nitrogenous base, a phosphate, and a deoxyribose sugar
molecule. The nitrogenous bases come in four unique specifications, these
being Adenine, Thymine, Cytosine and Guanine. The bases must be
complimentary, meaning that Adenine (also known as A) can only form a
hydrogen bond with Thymine (T) and Cytosine (C) can only form a bond
with Guanine. The hydrogen bond for A and T has two bonds, whilst the C
and G have three bonds, so they are slightly stronger. The deoxyribose
sugar and phosphate bond together on the edge of the nucleotide to
create the sugar phosphate backbone, which is essential to hold the
nucleotide together and protect its structure. The sugar molecule will then
bond to another phosphate which will have its own allocated base, and so
on, to create a polynucleotide. Each three nucleotides are grouped
together in a triplet, also known as a codon, and will code for a particular
amino acid, for example, GGC will create the code for glycine. Multiple
codons will work together to code for a chain of amino acids which will
produce a protein which can characterise a trait. A whole DNA strand will
have two of these complimentary strands, held together by the
complimentary bases. These strands are antiparallel, known as 3’ to 5’ or
5’ to 3’. On one strand, the first phosphate will bond to the 5th carbon of
the sugar and end of its 3rd carbon in a downwards motion and repeats
with the next phosphate bonding to the 3rd carbon, with the 5’ on top and
the 3’ underneath, so the 5’ to 3’ strand. The other strand bonds the same
way, but with the 3’ on top and the 5’ beneath, so it is the 3’ to 5’ end.
pg. 1
, S012617 : Joshua Sharp
Unit 13 : A
DNA Replication
DNA goes through many processes to replicate and reproduce to
provide genetic material to new cells. Before sexual and asexual
reproduction, DNA must replicate to increase the amounts of genetic
information available to new cells. The stage before reproduction is
known as interphase, where the cell carries out its usual functions
pg. 2
Unit 13 : A
DNA Replication and the Impact of Variation in
the DNA Sequence
Structure of DNA
DNA is a polymer comprised of two strands of genetic information in a
structure known as the double helix. Each respective strand is comprised
of a chain of nucleotides. In each nucleotide, there is three respective key
components, the nitrogenous base, a phosphate, and a deoxyribose sugar
molecule. The nitrogenous bases come in four unique specifications, these
being Adenine, Thymine, Cytosine and Guanine. The bases must be
complimentary, meaning that Adenine (also known as A) can only form a
hydrogen bond with Thymine (T) and Cytosine (C) can only form a bond
with Guanine. The hydrogen bond for A and T has two bonds, whilst the C
and G have three bonds, so they are slightly stronger. The deoxyribose
sugar and phosphate bond together on the edge of the nucleotide to
create the sugar phosphate backbone, which is essential to hold the
nucleotide together and protect its structure. The sugar molecule will then
bond to another phosphate which will have its own allocated base, and so
on, to create a polynucleotide. Each three nucleotides are grouped
together in a triplet, also known as a codon, and will code for a particular
amino acid, for example, GGC will create the code for glycine. Multiple
codons will work together to code for a chain of amino acids which will
produce a protein which can characterise a trait. A whole DNA strand will
have two of these complimentary strands, held together by the
complimentary bases. These strands are antiparallel, known as 3’ to 5’ or
5’ to 3’. On one strand, the first phosphate will bond to the 5th carbon of
the sugar and end of its 3rd carbon in a downwards motion and repeats
with the next phosphate bonding to the 3rd carbon, with the 5’ on top and
the 3’ underneath, so the 5’ to 3’ strand. The other strand bonds the same
way, but with the 3’ on top and the 5’ beneath, so it is the 3’ to 5’ end.
pg. 1
, S012617 : Joshua Sharp
Unit 13 : A
DNA Replication
DNA goes through many processes to replicate and reproduce to
provide genetic material to new cells. Before sexual and asexual
reproduction, DNA must replicate to increase the amounts of genetic
information available to new cells. The stage before reproduction is
known as interphase, where the cell carries out its usual functions
pg. 2
