Topic 2.7: DNA Replication, Transcription, and Translation Flashcards
What is the first step of DNA replication?
Helicase unwinds the double helix and separates the two polynucleotide strands
After Helicase unwinds the double helix and separates the two polynucleotide strands what is the next step of DNA replication?
DNA polymerase synthesises new strands from the two parental template strands
Define polymerase chain reaction (PCR)
The polymerase chain reaction (PCR) is an artificial method of replicating DNA under laboratory conditions
What is PCR used for?
The PCR technique is used to amplify large quantities of a specific sequence of DNA from an initial minute sample
Each reaction doubles the amount of DNA – a standard PCR sequence of 30 cycles creates over 1 billion copies (230)
What is the first step of polymerase chain reaction?
Denaturation – DNA sample is heated (~90ºC) to separate the two strands
After Denaturation – DNA sample is heated (~90ºC) to separate the two strands What is the next step of polymerase chain reaction?
Annealing – Sample is cooled (~55ºC) to allow primers to anneal (primers designate sequence to be copied)
After Annealing – Sample is cooled (~55ºC) to allow primers to anneal (primers designate sequence to be copied) What is the last step of polymerase chain reaction?
Elongation – Sample is heated to the optimal temperature for a heat-tolerant polymerase (Taq) to function (~75ºC)
Define taq polymerase
Taq polymerase is an enzyme isolated from the thermophilic bacterium Thermus aquaticus
Define transcription
Transcription is the process by which an RNA sequence is produced from a DNA template
What is the first step of transcription?
RNA polymerase separates the DNA strands and synthesises a complementary RNA copy from one of the DNA strands
After RNA polymerase separates the DNA strands and synthesises a complementary RNA copy from one of the DNA strands, what is the next step of transcription?
When the DNA strands are separated, ribonucleotide triphosphates align opposite their exposed complementary base partner
After When the DNA strands are separated, ribonucleotide triphosphates align opposite their exposed complementary base partner, what is the next step of transcription?
RNA polymerase removes the additional phosphate groups and uses the energy from this cleavage to covalently join the nucleotide to the growing sequence
After RNA polymerase removes the additional phosphate groups and uses the energy from this cleavage to covalently join the nucleotide to the growing sequence, what is the last step of transcription?
Once the RNA sequence has been synthesised, RNA polymerase detaches from the DNA molecule and the double helix reforms
What is the antisense strand?
The strand that is transcribed is called the antisense strand and is complementary to the RNA sequence
What is the sense strand?
The strand that is not transcribed is called the sense strand and is identical to the RNA sequence (with U instead of T)
Define codons
triplets of bases
Define translation
Translation is the process of protein synthesis in which the genetic information encoded in mRNA is translated into a sequence of amino acids on a polypeptide chain
What is the first step of translation?
Ribosomes bind to mRNA in the cytoplasm and move along the molecule in a 5’ – 3’ direction until it reaches a start codon (AUG)
After Ribosomes bind to mRNA in the cytoplasm and move along the molecule in a 5’ – 3’ direction until it reaches a start codon (AUG), What is the next step of translation?
Anticodons on tRNA molecules align opposite appropriate codons according to complementary base pairing (e.g. AUG = UAC)
After Anticodons on tRNA molecules align opposite appropriate codons according to complementary base pairing (e.g. AUG = UAC)), What is the next step of translation?
Each tRNA molecule carries a specific amino acid (according to the genetic code)
After Each tRNA molecule carries a specific amino acid (according to the genetic code), What is the next step of translation?
Ribosomes catalyse the formation of peptide bonds between adjacent amino acids (via condensation reactions)
After Ribosomes catalyse the formation of peptide bonds between adjacent amino acids (via condensation reactions), What is the next step of translation?
The ribosome moves along the mRNA molecule synthesising a polypeptide chain until it reaches a stop codon
After The ribosome moves along the mRNA molecule synthesising a polypeptide chain until it reaches a stop codon, what is the last step of translation?
At this point translation ceases and the polypeptide chain is released
What is the first step of insulin production via recombinant gene transfer?
The gene responsible for insulin production is extracted from a human cell
After The gene responsible for insulin production is extracted from a human cell, What is the next step of insulin production via recombinant gene transfer?
It is spliced into a plasmid vector (for autonomous replication and expression) before being inserted into a bacterial cell
After It is spliced into a plasmid vector (for autonomous replication and expression) before being inserted into a bacterial celll, What is the next step of insulin production via recombinant gene transfer?
The transgenic bacteria (typically E. coli) are then selected and cultured in a fermentation tank (to increase bacterial numbers)
After The transgenic bacteria (typically E. coli) are then selected and cultured in a fermentation tank (to increase bacterial numbers), What is the last step of insulin production via recombinant gene transfer?
The bacteria now produce human insulin, which is harvested, purified and packaged for human use (i.e. by diabetics)
