DNA AND GENES
Nucleotide structure and function
DNA is a polymer of nucleotides also known as a polynucleotide that forms two
polynucleotide chains. Each nucleotide contains a phosphate group, a sugar group called
deoxyribose and a nitrogenous base including two purines (adenine and guanine) and
two pyrimidines (cytosine and thymine). Adenine and guanine ae purines because they
have a two-ring structure whilst cytosine and thymine have one ring structure. Adenine
and guanine are also held by two hydrogen bonds whilst cytosine and thymine are held
by three hydrogen bonds. Essentially, adenine is complementary base pairs with guanine
and cytosine is complementary base pairs with thymine. DNA is made up of two single
strands (double stranded) which forms a double helix held together by hydrogen bonds
between their bases. DNA contains and stores information which provide instructions
that the cell uses to make protein. Protein is very important as it determines the
characteristics of an organism of specialised cells. It encodes the sequence of amino acid
using the genetic code to produce protein. It is also responsible for carrying and
retaining the genetic information in the cell for the development of living things.
Messenger RNA (mRNA) is a polymer of ribonucleotides with small monomer
covalently bonded together to form just one polynucleotide chain, unlike DNA mRNA is
single stranded and are held together by phosphodiester bonds. Each ribonucleotide
includes a pentose sugar called ribose. A phosphate group and one of the four
nitrogenous bases which contains adenine and uracil, cytosine and guanine. mRNA
function is to carry genetic information from the DNA in the nucleus/protein to its
ribosomes where the protein is synthesized.
Transfer RNA (tRNA) has a special folded structure with three hairpin loops that forms
the shape of a three leafed clover. one of the hairpin loops consists of a sequence known
as a anticodon which can decode a mRNA code, tRNA molecule also has amino acid
attached to its end. tRNA is a type of RNA molecule which contains a set of three
nucleotides called an anticodon which can bind to one or few specific types of mRNA
codons, it is also single stranded. Its function is to pair an mRNA codon with the amino
acid it codes for so that the amino acid can continue growing into a peptide chain.it also
synthesis in the cytoplasm.
Ribosomal RNA (rRNA) is shaped as a sphere (a complex structure) which moves
along a mRNA molecule and ensures it has a proper alignment. The size of a rRNA
molecule vary from 30S to 60S. unlike the other codon It does not have an anticodon or
codon sequence as its main role is to ensure a structural framework for the formation of
ribosomes, they also bind to tRNA for protein synthesis and ensure appropriate position
to the ribosomes during protein synthesis. rRNA is synthesised in the nucleolus.
, Small interfering RNA molecules (SiRNA)- they are short double stranded DNA
molecules, 21 nucleotides long. They are used to help regulate gene activity by breaking
down mRNA. They avoid specific protein being created based on their nucleotide
sequences of their corresponding mRNA. SiRNA are created to reduce the translation of
specific mRNAs, this is performed to lower the production of proteins.
DNA replication
DNA replication occurs in the nucleus inside the cell
Key terms: DNA Helicase, DNA Polymerase, Free floating DNA nucleotides, hydrogen
bonds, phosphodiester binds, template strand, complementary base pairing and sugar
phosphate backbone.
Three stages involved: initiation, elongation and termination
Initiation
DNA Helicase unwinds the double helix and exposes two strands so they can be used as
a template for replication, this is done by breaking the hydrogen bonds between the
complementary base pairs (the two strands) and separating them into individual strands
creating a replication fork. The two new strands now act as a template for making an
new strand. DNA polymerase generates a new kind of complementary strand adding
nucleotide to the new chain initiated by the enzyme DNA primer expanding new strands
of DNA. DNA polymerase replicates DNA molecules to create a new strand of DNA.
Elongation
DNA polymerase binds to the DNA primer and begin synthesising a new strand and will
make the new stand of DNA and can only add bases in one direction. one of the new
strands of DNA (leading strand) is made continuously by binding to multiple primers, the
other strand (the lagging strand) run in the opposite direction so it cannot be made
continuously also called okazaki fragment which are disjointed. DNA polymerase adds
nucleotides in short sections to overcome to the directionality problem.
Termination
The process of expanding the DNA strands continues until there is no more DNA
template to replicate once DNA synthesis has finished. the leading strand act a template
and DNA polymerase adds nucleotides to the new strand. RNA primers are removed at
the beginning of each okazaki fragment (lagging strand), the sequence is synthesized by
another DNA polymerase. DNA ligases form covalent bonds between the sugar of one
nucleotide and the phosphate group of the adjacent nucleotide forming new backbones.
DNA ligase fills in the gaps between all okazaki fragments and the parent strand and
complementary DNA strand (the new strand) coils together to form a double helix
producing two molecules consisting of one new strand and one old strand of DNA.
Transcription
What nucleic acids are involved and what do they do?
mRNA- it carries the coding sequences for protein synthesis
tRNA- it matches the amino acids with the correct codons
DNA- it stores the template
Stages
Nucleotide structure and function
DNA is a polymer of nucleotides also known as a polynucleotide that forms two
polynucleotide chains. Each nucleotide contains a phosphate group, a sugar group called
deoxyribose and a nitrogenous base including two purines (adenine and guanine) and
two pyrimidines (cytosine and thymine). Adenine and guanine ae purines because they
have a two-ring structure whilst cytosine and thymine have one ring structure. Adenine
and guanine are also held by two hydrogen bonds whilst cytosine and thymine are held
by three hydrogen bonds. Essentially, adenine is complementary base pairs with guanine
and cytosine is complementary base pairs with thymine. DNA is made up of two single
strands (double stranded) which forms a double helix held together by hydrogen bonds
between their bases. DNA contains and stores information which provide instructions
that the cell uses to make protein. Protein is very important as it determines the
characteristics of an organism of specialised cells. It encodes the sequence of amino acid
using the genetic code to produce protein. It is also responsible for carrying and
retaining the genetic information in the cell for the development of living things.
Messenger RNA (mRNA) is a polymer of ribonucleotides with small monomer
covalently bonded together to form just one polynucleotide chain, unlike DNA mRNA is
single stranded and are held together by phosphodiester bonds. Each ribonucleotide
includes a pentose sugar called ribose. A phosphate group and one of the four
nitrogenous bases which contains adenine and uracil, cytosine and guanine. mRNA
function is to carry genetic information from the DNA in the nucleus/protein to its
ribosomes where the protein is synthesized.
Transfer RNA (tRNA) has a special folded structure with three hairpin loops that forms
the shape of a three leafed clover. one of the hairpin loops consists of a sequence known
as a anticodon which can decode a mRNA code, tRNA molecule also has amino acid
attached to its end. tRNA is a type of RNA molecule which contains a set of three
nucleotides called an anticodon which can bind to one or few specific types of mRNA
codons, it is also single stranded. Its function is to pair an mRNA codon with the amino
acid it codes for so that the amino acid can continue growing into a peptide chain.it also
synthesis in the cytoplasm.
Ribosomal RNA (rRNA) is shaped as a sphere (a complex structure) which moves
along a mRNA molecule and ensures it has a proper alignment. The size of a rRNA
molecule vary from 30S to 60S. unlike the other codon It does not have an anticodon or
codon sequence as its main role is to ensure a structural framework for the formation of
ribosomes, they also bind to tRNA for protein synthesis and ensure appropriate position
to the ribosomes during protein synthesis. rRNA is synthesised in the nucleolus.
, Small interfering RNA molecules (SiRNA)- they are short double stranded DNA
molecules, 21 nucleotides long. They are used to help regulate gene activity by breaking
down mRNA. They avoid specific protein being created based on their nucleotide
sequences of their corresponding mRNA. SiRNA are created to reduce the translation of
specific mRNAs, this is performed to lower the production of proteins.
DNA replication
DNA replication occurs in the nucleus inside the cell
Key terms: DNA Helicase, DNA Polymerase, Free floating DNA nucleotides, hydrogen
bonds, phosphodiester binds, template strand, complementary base pairing and sugar
phosphate backbone.
Three stages involved: initiation, elongation and termination
Initiation
DNA Helicase unwinds the double helix and exposes two strands so they can be used as
a template for replication, this is done by breaking the hydrogen bonds between the
complementary base pairs (the two strands) and separating them into individual strands
creating a replication fork. The two new strands now act as a template for making an
new strand. DNA polymerase generates a new kind of complementary strand adding
nucleotide to the new chain initiated by the enzyme DNA primer expanding new strands
of DNA. DNA polymerase replicates DNA molecules to create a new strand of DNA.
Elongation
DNA polymerase binds to the DNA primer and begin synthesising a new strand and will
make the new stand of DNA and can only add bases in one direction. one of the new
strands of DNA (leading strand) is made continuously by binding to multiple primers, the
other strand (the lagging strand) run in the opposite direction so it cannot be made
continuously also called okazaki fragment which are disjointed. DNA polymerase adds
nucleotides in short sections to overcome to the directionality problem.
Termination
The process of expanding the DNA strands continues until there is no more DNA
template to replicate once DNA synthesis has finished. the leading strand act a template
and DNA polymerase adds nucleotides to the new strand. RNA primers are removed at
the beginning of each okazaki fragment (lagging strand), the sequence is synthesized by
another DNA polymerase. DNA ligases form covalent bonds between the sugar of one
nucleotide and the phosphate group of the adjacent nucleotide forming new backbones.
DNA ligase fills in the gaps between all okazaki fragments and the parent strand and
complementary DNA strand (the new strand) coils together to form a double helix
producing two molecules consisting of one new strand and one old strand of DNA.
Transcription
What nucleic acids are involved and what do they do?
mRNA- it carries the coding sequences for protein synthesis
tRNA- it matches the amino acids with the correct codons
DNA- it stores the template
Stages
