Unit 5
Gene expression
Gene - A segment of DNA carrying a code for a polypeptide
Polypeptide - A chain of amino acids linked together by peptide bonds which are then folded together into a protein to carry out a function in a cell.
The firsts step of that that happens is that the DNA is transcribed into mRNA
Then the mRNA moves to the ribosome to be translated into a protein by putting amino acids together.
Then the protein folding occurs when the polypeptide take on the shape needed for its function
DNA
DNA's Nitrogenous bases
Adenine
Guanine
Thymine
Cytosine
Pyrimidines, molecules that have only 1 ring in their structure
Purines, molecules the have 2 rings in their structure
The levels of Thymine and Adenine are about the same in DNA, and the levels of Guanine and cytosine are about the same since they are base pairs.
The bases line up to create DNA's double helix structure.
DNA has to stay in the nucleus.
DNA contains deoxyribose as the sugar.
DNA contains a phosphate group
Biotech terminology
Genetic engineering - adding genes that could normally not be in an organism in order to make a particular protein.
Recombinant DNA - the new genetic material in the organism
Plasmid - a small circular piece of DNA that can have genes easily added to it, usually by using restriction enzymes
Restriction enzymes - enzymes that act like scissors and cut DNA at specific spots
RNA
forms of RNA
rRNA - ribosomal RNA combines with the ribosomal proteins to makeup the actual ribosome.
tRNA - TransferRNA - attaches to amino acids and then transfers them to the ribosome during translation.
mRNA - Messenger RNA: the instructions for making a protein are encoded within its sequence of nucleotides.
RNA is made during a process called transcription, where a DNA sequence is copied into a sequence made of RNA bases that base pair by hydrogen bonding to the DNA molecule.
RNA includes the Sugar Ribose,
RNA includes a phosphate group
RNA’s nitrogenous bases are Adenine, Uracil, Guanine, Cytosine.
Uracil is a pyrimidine, like thymine from DNA. Similarly to thymine Uracil pairs with Adenine.
Levels of protein structure
Secondary structure, there are 2 main structures, beta-sheets that fold back and forth and alpha helices that curl.
Tertiary structure is the final folded structure that the protein chain will make
Primary protein structure, This level is the sequence of the amino acids in a chain called a polypeptide.
Quaternary structure is the final structure for proteins that have multiple chain subunits.
How to make recombinant DNA
They then get a plasmid and then the gene is cut with a restriction enzyme.
Scientists use the same restriction enzyme on the plasmid.
They get the gene that they want to use.
The cut ends of the plasmid DNA and the human DNA will attach from a loops of plasmid DNA called recombinant DNA.
Restriction Enzyme Information
Blunt ends occur when the enzyme cuts through both strands of DNA and there are no bases hanging over.
The restriction sites are DNA palindromes, the same forwards and backward.
Sticky ends occur when the enzyme cuts the DNA and eaves some bases hanging over on one side.
They can create sticky or blunt ends.
Translation - Translation has three steps, initiation, elongation, termination.
Transcription - The enzyme RNA polymerase finds the start of the gene and binds to the DNA. Once it attaches it begins to unwind the DNA and match complementary RNA bases to the template strand of the DNA and connects the RNA together to make the mRNA strand then it rewinds the DNA.
Elongation: tRNAs bring amino acids one by one to add to the polypeptide chain.
Initiation: Transitional complex forms and tRNA brings the first amino acid in the polypeptide chain to bind to start codon on mRNA.
Bacterial Transformation steps
Competent cell preparation - Researchers use a chemical treatment to make the cells competent. The process alters the bacteria’s plasma membranes in such a way that plasmids can pass through the bacteria’s cellwall and then the plasma membrane.
Transformation - The goal of transformation is to pick up DNA plasmids from their environment. The plasmids and the cells are negatively charged which is changed by adding things to neutralize their charge.
Recovery - The temperature is increased and then reduced back creating a leaky plasma membrane allowing it to take up a plasmid.
Plating - They are put on agar plates and left to incubate for 24 hours the ones that survive go on to form a colony.