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DNA & Translation
Transcript of DNA & Translation
Protein Synthesis DNA Deoxyribonucleic acid DNA is the genetic material in living organisms
Can be copied It is a blueprint for the construction and behaviour of cells
These instructions can be passed on to any ´daughter cells´. Structure of DNA Cells contain a nucleus
The nucleus contains a number of chromosomes, 46 in humans. DNA is the chemical which makes chromosomes The chromosomes are arranged split into units called genes that code for a particular characteristic DNA structure is like a twisted ladder
It is known as the ´double helix´
It has two backbones of sugar-phosphate molecules
It has ´rungs´ of pairs of nitrogen containing bases joined by hydrogen bonds
DNA is made up of NUCLEOTIDES REMEBER: Nucleotides contain,
1) a Nitrogen containing BASE
2) a pentose sugar
3) a phosphate group
Nucleotides are thereforethe MONOMER of the DNA POLYMER
DNA is know as a NUCLEIC ACID There are only 4 different bases that can be found in any DNA Nucleotide
Adenine (A) and Guanine (G) - These are known as PURINE bases
Thymine (T) and Cytosine (C) - These are know as PYRAMIDINE bases
DNA shows COMPLEMENTARY base pairing.
Adenine will only pair with Thymine / Guanine will only pair with Cytosine Nnumber of hydrogen bonds??? DISCOVERY OF DNA BY WATSON AND CRICK (1953) RNA Ribonucleic Acid RNA is another type of nucleic acid
Different types of RNA are used during DNA and Protein synthesis
It is similar in structure to DNA but with a few important differences The diagram Identifies 3 main differences
1) RNA is a single helix, DNA is double
2) DNA´s Thymine base is replaced by Uracil (U)
3) DNA contains a deoxyribose sugar,
RNA contains a ribose sugar. Can you find 3 differences???? DNA Replication The double helix structure enables the DNA malecule to be replicated Because half of the original DNA strand is kept this process is called
SEMI-CONSERVATIVE REPLICATION Protein Synthesis The Genetic Code How can a single type of molecule control all of the activities of a cell? All of the functions of a cell depend on chemical reactions
All chemical reactions depend on ENZYMES
Enzymes are proteins
DNA is the code for proteins!!! So how does this code work? REMEMBER that the primary structure of a protein
is a chain of AMINO ACIDS The shape and behaviour of a protein depends on the exact sequence
There are only 20 acids which make up all proteins
The sequence of bases in the DNA codes for each amino acid
Each amino acid has a 3 base code, or TRIPLET CODE
This is called the CODON I want you all to write a 30 letter genetic code(10 amino acids). Change with a partner and see if they can crack it! The Human Genome In 2003, the 13 year long Human Genome Project to decode the Human genome (the total set of genes in a human cell) was complete.
They decoded about 25,000 genes
These 25,000 genes involved about 3,000,000,000 base pairs!!! Ok. So we know what the code is and how it works.
But how do we actually go from the DNA to making a protein?
This process is called PROTEIN SYNTHESIS.
It involves to linked processes; Translation and Transcription TRANSCRIPTION 1. Part of the DNA unwinds (DNA Polymerase)
2. Free RNA nucleotides pair up with exposed DNA bases of one strand only
3. RNA nucleotides form a single strand
4. We now have a copy of the DNA, called Messenger RNA (mRNA)
THIS OCCURS IN THE NUCLEUS HOWEVER!!!
The mRNA code will be different to the orginal DNA strand.
HOW??? 1. It will be the opposite sequence
2. TheThymine of the DNA will be replaced with a Uracil in the mRNA Go back to your 30 base pair section of DNA code
Write down what the code for mRNA transcibed from this code would look like TRANSLATION 1. The mRNA leaves the nucleus through the nuclear pore and attaches to the RIBOSOME
2. TRANSFER RNA (tRNA) in the cytoplasm have a triplet of bases at one end(ANTI-CODON) and an area for an amino acid to attach at another.
3. Each tRNAs anti-codon links to its complementary codon on the mRNA.
4. Two tRNAs can fit into the ribosome at the same time. A polypetide bond forms between the two amino acids they carry
5. This continues until a complete polypeptide (protein) is formed