Topic 2.7: DNA Replication, Transcription, and Translation

Question 1

What is the first step of DNA replication?

Answer 1

Helicase unwinds the double helix and separates the two polynucleotide strands

Question 2

After Helicase unwinds the double helix and separates the two polynucleotide strands what is the next step of DNA replication?

Answer 2

DNA polymerase synthesises new strands from the two parental template strands

Question 3

Define polymerase chain reaction (PCR)

Answer 3

The polymerase chain reaction (PCR) is an artificial method of replicating DNA under laboratory conditions

Question 4

What is PCR used for?

Answer 4

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)

Question 5

What is the first step of polymerase chain reaction?

Answer 5

Denaturation – DNA sample is heated (~90ºC) to separate the two strands

Question 6

After Denaturation – DNA sample is heated (~90ºC) to separate the two strands What is the next step of polymerase chain reaction?

Answer 6

Annealing – Sample is cooled (~55ºC) to allow primers to anneal (primers designate sequence to be copied)

Question 7

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?

Answer 7

Elongation – Sample is heated to the optimal temperature for a heat-tolerant polymerase (Taq) to function (~75ºC)

Question 8

Define taq polymerase

Answer 8

Taq polymerase is an enzyme isolated from the thermophilic bacterium Thermus aquaticus

Question 9

Define transcription

Answer 9

Transcription is the process by which an RNA sequence is produced from a DNA template

Question 10

What is the first step of transcription?

Answer 10

RNA polymerase separates the DNA strands and synthesises a complementary RNA copy from one of the DNA strands

Question 11

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?

Answer 11

When the DNA strands are separated, ribonucleotide triphosphates align opposite their exposed complementary base partner

Question 12

After When the DNA strands are separated, ribonucleotide triphosphates align opposite their exposed complementary base partner, what is the next step of transcription?

Answer 12

RNA polymerase removes the additional phosphate groups and uses the energy from this cleavage to covalently join the nucleotide to the growing sequence

Question 13

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?

Answer 13

Once the RNA sequence has been synthesised, RNA polymerase detaches from the DNA molecule and the double helix reforms

Question 14

What is the antisense strand?

Answer 14

The strand that is transcribed is called the antisense strand and is complementary to the RNA sequence

Question 15

What is the sense strand?

Answer 15

The strand that is not transcribed is called the sense strand and is identical to the RNA sequence (with U instead of T)

Question 16

Define codons

Answer 16

triplets of bases

Question 17

Define translation

Answer 17

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

Question 18

What is the first step of translation?

Answer 18

Ribosomes bind to mRNA in the cytoplasm and move along the molecule in a 5’ – 3’ direction until it reaches a start codon (AUG)

Question 19

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?

Answer 19

Anticodons on tRNA molecules align opposite appropriate codons according to complementary base pairing (e.g. AUG = UAC)

Question 20

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?

Answer 20

Each tRNA molecule carries a specific amino acid (according to the genetic code)

Question 21

After Each tRNA molecule carries a specific amino acid (according to the genetic code), What is the next step of translation?

Answer 21

Ribosomes catalyse the formation of peptide bonds between adjacent amino acids (via condensation reactions)

Question 22

After Ribosomes catalyse the formation of peptide bonds between adjacent amino acids (via condensation reactions), What is the next step of translation?

Answer 22

The ribosome moves along the mRNA molecule synthesising a polypeptide chain until it reaches a stop codon

Question 23

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?

Answer 23

At this point translation ceases and the polypeptide chain is released

Question 24

What is the first step of insulin production via recombinant gene transfer?

Answer 24

The gene responsible for insulin production is extracted from a human cell

Question 25

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?

Answer 25

It is spliced into a plasmid vector (for autonomous replication and expression) before being inserted into a bacterial cell

Question 26

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?

Answer 26

The transgenic bacteria (typically E. coli) are then selected and cultured in a fermentation tank (to increase bacterial numbers)

Question 27

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?

Answer 27

The bacteria now produce human insulin, which is harvested, purified and packaged for human use (i.e. by diabetics)