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Nucleic Acid Structure:
- Are molecules that are built in a way that allows them to contain info that codes
for all different elements in an organism's organic existence.
- If a feature EXISTS in an organism = it is coded for by nucleic acids.
= Do this by controlling protein synthesis.
- This controls hormones, enzymes and carrier molecules SO it controls the
organism.
- There are TWO key Nucleic Acids
1. DNA = Deoxyribonucleic Acid
2. RNA = Ribonucleic Acid
Deoxyribonucleic Acid (DNA):
- Found in the nucleus of the cell.
- Forms all chromosomes.
- Unwound it forms a network of thin threads called Chromatin Networks.
- Each chromosome is made of a thin thread of DNA wrapped around a protein
called a Histone. (2m per cell)
- Small amounts are found in mitochondria and in chloroplasts.
= Reasons for this are evolutionary.
- 2 key scientists worked on its structure.
1. Watson.
2. Crick.
3. Franklin.
- It is a ladder (scalariform) twisted into a double helix (spiral staircase).
- It's made of units (monomers) joined together into a massive super molecule
(polymer).
- The monomers are called Nucleotides.
- Nucleotides are made up of
1. Sugar molecule (deoxyribose sugar)
2. Phosphate molecule.
3. Nitrogenous base. (are only 4 types)
,- Nitrogenous bases
1. Adenine = A
2. Thymine = T
3. Guanine = G
4. Cytosine = C
- The bases are divided into two big groups.
= The Purines (Adenine + Guanine) and the Pyramids (Cytosine + Thymine).
- Bases in the rungs are linked by weak Hydrogen bonds.
- These link in a specific way. (never varies and is always like this)
1. A with T
2. C with G
- FUNCTION
1. Carries the coded genetic information of the cell.
2. Can replicate.
3. Supervises the manufacture of all proteins.
- Replication is the process of making a new DNA molecule from the existing one
that is identical to the parent molecule.
= Done during interphase.
= Catalysed by an enzyme called DNA Polymerase.
= Process follows
1. Double helix unwinds.
2. Hydrogen bonds break (unzipping). (weak bonds)
3. Each single chain is then exposed.
4. Free nucleotides attach to complementary bases.
5. Weak hydrogen bonds reform. (each new double stranded bond)
6. Twists back up again.
7. Takes a very short period of time.
8. This is catalyzed by DNA Polymerase. (semi-conservative, reduces
mutation)
, Ribonucleic Acid (RNA):
- It is made in the nucleus by DNA.
- Are three different types of RNA. (all involved in protein synthesis)
1. Messenger RNA (m-RNA)
2. Transfer RNA (t-RNA)
3. Ribosomal RNA (r-RNA)
- Differences in it compared to DNA
1. Always single stranded.
2. Shorter than DNA.
3. No Thymine (T) is replaced with Uracil (U).
4. Sugar is Ribose and deoxyribose.
- It acts as a messenger for DNA.
- Is involved in protein synthesis.
Protein Synthesis:
- Only two phases
1. Transcription
2. Translation (includes transfer)
- Are 20 Amino Acids.
- Order of the amino acids determine the type of protein made.
- Need 50 to make a protein.
- Have primary, secondary and tertiary structure.
- All needed to be 100% accurate is the protein to be made to work properly and
perform its function.
- The DNA code is laid down in triplet sets of bases.
- Each of these is called a Codon.
- Each Codon codes for a single amino acid.
= Eg) Codon CAG is the one of Valine.
- A gene is a series of nucleotides that together have a sequence of codons that
code for the making of 1 protein.
- The role of m-RNA
= Made using a process that works almost exactly the same way as replication.
= A complementary strand of m-RNA is made from a section of unzipped DNA
(transcription).
= The base Uracil is substituted where necessary.
= The short-stranded message is then exported from the nucleus through a
nuclear pore (transfer).
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