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Unit 11A applied science DISTINCTION
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Unit 11A assignmentP1- Explain the structure and function of DNA and various nucleic acids
Nucleotide structure
In DNA and RNA nucleotides are present and they are made up of these three components:
Nitrogenous base:
Nitrogenous bases are classified into two types:
purines and pyrimidines. Purines are adenine and
guanine. Pyrimidines are cytosine, thymine, and
uracil. The bases of DNA are adenine (A), thymine
(T), guanine (G), and cytosine (C). The bases of RNA
are adenine, guanine, uracil, and cytosine.
Pentose sugar (5-carbon sugar):
The sugar in DNA is 2'-deoxyribose. Ribose is the
sugar in RNA. Ribose and deoxyribose are both 5-
carbon sugars. To help in keeping track of where
each group is attached the carbons are numbered
consecutively. The only difference between the two
sugars is that 2’deoxyribose has one less oxygen
atom linked to the second carbon atom.
Phosphate group:
The phosphorus atom is the central atom. One oxygen atom is connected to the sugar's 5-carbon as
well as the phosphorus atom. When phosphate groups come together to form chains like ATP, the
connection looks like O-P-O-P-O-P-O, with two additional oxygen atoms attached to each
phosphorus.
DNA structure
DNA is a polynucleotide, which means that it is made up of various nucleotides that are linked
together in a continuous chain. DNA molecules are made up of two polynucleotide strands that run
antiparallel. The sugar-phosphate foundation of each DNA polynucleotide strand is made up of
alternating deoxyribose sugars and phosphate groups that are bound together which
are phosphodiester bonds, which are covalent bonds.
The phosphodiester bonds connect the 5-carbon of one deoxyribose sugar molecule to the
phosphate group of the same nucleotide, which is connected to the 3-carbon of the deoxyribose
sugar molecule of the next nucleotide in the strand by another phosphodiester bond.
Every DNA polynucleotide strand has a 3’ and a 5’ end which correspond to which carbon on the
pentose sugar they bond to another nucleotide.
DNA has hydrogen bonds which holds the two strands of DNA together. Adenine pairs with thymine
to form two hydrogen bonds. Guanine pairs with pyrimidine cytosine to form three hydrogen bonds.
DNA forms a double helix in order to protect the DNA and its information from damage which would
be detrimental to the organism.
RNA
, RNA, also known as ribonucleic acid, is a nucleotide polymer composed of a ribose sugar, a
phosphate, and bases such as adenine, guanine, cytosine, and uracil.
RNA is a single- strand helix
The strand has a 5’ with a phosphate group and a 3’end with a hydroxl group
The ribonucleotides are linked by phosphodiester bonds
Nitrogenous bases in ribonucleotides include adenine, cytosine, uracil and guanine
Types of RNA:
There are three types of RNA these include:
mRNA
Your genetic information would never be utilised by your body if mRNA did not exist.
Proteins would never be created. And your body would be unable to fulfil its
functions. Messenger ribonucleic acid is a single-stranded molecule that transports
genetic code from the nucleus of a cell to the cell's ribosomes.
tRNA
Transfer RNAs are adaptor molecules that transfer amino acids to the protein
synthesis machinery during translation to convert genetic information into protein
sequence.
rRNA
Ribosomal RNA plays a role in protein synthesis by binding to messenger RNA and
transfer RNA to verify that the codon sequence of the mRNA is correctly translated
into amino acid sequence in proteins.
Comparisons between DNA and RNA
Similarities between DNA and RNA:
1. They are both biomolecules that are synthesized by the polymerase enzyme
2. Both are polynucleotide chains made up of a single nucleotide monomer
3. Both are made up of five carbon-pentose sugar, phosphate, and nitrogenous bases
4. They both can be precipitated using alcohol
Differences between DNA and RNA:
1. DNA has adenine, thymine, cytosine, and guanine whereas RNA uses adenine, uracil, cytosine, and
guanine. Uracil differs from thymine in that its ring lacks a methyl group.
2. DNA is a double stranded molecule whilst RNA is single stranded
3.DNA is stable under alkaline conditions but RNA is unusable
4. Deoxyribose is found in DNA whereas in RNA ribose is found
5. In human DNA is in charge of storing and transmitting genetic information whereas RNA codes for
amino acids and acts as a messenger between DNA and ribosomes.
DNA replication
, Why does DNA replicate?
DNA needs to replicate so new cells can be created so it can be used to help regulate and prepared
damaged cells or tissues.
Step 1: Replication fork formation
The double-stranded molecule of DNA must be "unzipped" into two single strands before it can be
copied. The DNA is unwinded by the enzyme known as DNA helicase, which disrupts the hydrogen
bonds between the pairs which intern separates it.
Step 2: Primer Binding
Once the DNA is separated, RNA called primer binds to the 3’ end of the strand. Primers are made by
the enzyme DNA primase
Step 3: Elongation
During elongation the enzyme DNA polymerase adds DNA nucleotides to the 3’ end of the newly
created polynucleotide strand
Step 4: Termination
After forming both the continuous and discontinuous strands, an enzyme called exonuclease
removes all RNA primers from the original strands. Another enzyme known as DNA ligase connects
Okazaki fragments to produce a single united strand. Telomerase is a type of DNA polymerase
enzyme that catalyses the synthesis of telomere sequences at the ends of DNA.
The enzymes involved in DNA replication include:
1. Helicases which unwind the DNA
2. Primase which lays down RNA primers
3. Gyrase which relieves the build-up of torque during the unwinding
4. DNA polymerase III which is the main DNA synthesis enzyme
5. DNA polymerase I which replaces RNA primers with DNA
6. Ligase which fills in the gaps
M1- Discuss the functional role of nucleic acids in DNA in the stages of protein synthesis
Genetic code
Deoxyribonucleic acid is composed of chemical building blocks known as
nucleotides, which are composed of three parts: a phosphate group, a sugar
group, and one of four kinds of nitrogen bases. The nucleotides in DNA are
connected into double helix strands, with the phosphate and sugar groups
alternating. The importance of genetics in this scenario is that the way DNA is
constructed determines the qualities we receive from our parents. For example,
the sequence ATCGTT may result in blue eyes, whereas ATCGCT may result in
brown eyes, and this genetic code sequence is handed down through
generations. We can see that there is a genetic code within the DNA; the
instructions of this genetic code are included within the DNA and advise the cell
on how to produce a certain protein. The "letters" of the DNA code are A, C, G,
and T, which make up the nucleotide bases of DNA. These are denoted by the
letters Adenine (A), Cytosine (C), Guanine (G), and Thymine (T) (T). Genetics plays a
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