Bio U2 - 2.7

Question 1

Describe the meaning of “semiconservative” in relation to DNA replication.

Answer 1

New DNA is formed by one new strand and one strand coming from the original DNA.

Question 2

Explain the role of complementary base pairing in DNA replication.

Question 3

State why DNA strands must be separated prior to replication.

Answer 3

Because there is tension between the strands as they are coiled and wrapped around each other

Question 4

Outline two functions of helicase.

Answer 4

Unwinds the DNA at the origin of replication and breaks hydrogen bonds between both strands of DNA.

Question 5

State the role of the origin of replication in DNA replication.

Answer 5

It is at the origin of replication that the Helicase enzymes can begin moving in both directions and being unwinding the DNA.

Question 6

Contrast the number of origins in prokaryotic cells to the number in eukaryotic cells.

Answer 6

Prokaryotic cells there is only one origin but in Eukaryotic cell there are 100s to 1000s of origins

Question 7

Describe the movement of DNA polymerase along the DNA template strand.

Answer 7

5’ to 3’

Question 8

Describe the action of DNA polymerase III in pairing nucleotides during DNA replication.

Answer 8

DNA polymerase III adds DNA nuceloside triphosphate to the 3’ end of the nucleotide (sugar part)

Question 9

DNA polymerase continues to move along the template strand creating new strands with a base sequence complementary to the template strand – it does this with a very high degree of fidelity (very few mistakes made)

Answer 9

DNA Polymerase I is responsible for proofreading and drastically reducing the amount of errors

Question 10

Define transcription.

Answer 10

Transcription is the synthesis of mRNA copied from the DNA base sequences from a RNA polymerase.

Question 11

Outline the process of transcription, including the role of RNA polymerase and complementary base pairing.

Answer 11

Transcription happens in the nucleus, mitochondria, and chloroplasts or eukaryotic cells and in the cytoplasm of prokaryotic cells.
RNA polymerase makes mRNA from the antisense strand of the DNA as it is in 3’ to 5’ direction and the RNA polymerase goes from 5’ to 3’ only.

Question 12

Identify the sense and antisense strands of DNA given a diagram of translation.​

Answer 12

Sense: 5’ to 3’
Antisense: 3’ to 5’

Question 13

Define translation.

Answer 13

Translation is the process of decoding mRNA into codons and forming proteins

Question 14

State the location of translation in the cell.​

Answer 14

Prokaryotes: Cytoplasm
Eukaryotes: Cytoplasmic ribossomes or Rough ER

Question 15

Outline the role of messenger RNA in translation.​

Answer 15

The mRNA forms the template for the for protein synthesis

Question 16

Define codon, redundant and degenerate as related to the genetic code.

Answer 16

Codon: three nucleotides form a codon and these code for specific amino acids
Redundant and Degenerate: this means that some amino acids can be coded by more than one codon

Question 17

Explain how using a 4 letters nucleic acid “language” can code for a “language” of 20 amino acid letters in proteins.

Answer 17

The order of three nucleotides make one of the 20 amino acids. Now, there are only 20 amino acids as the process is redundant and degenerate, meaning that there can be multiple codons that code for one amino acids.

Question 18

Outline the role of complementary base pairing between mRNA and tRNA in translation.

Question 19

Outline the source and use of pharmaceutical insulin prior to the use of gene transfer technology.

Answer 19

Before, insulin used to be extracted from pigs

Question 20

Compare dispersive, conservative and semi-conservative replication.

Answer 20

Dispersive: Random strands of the original DNA would be present in the new DNA
Conservative: The new DNA is entirely copied from the original DNA strand such that both have no directly shared parts
Semi-Conservative: Half of the original DNA is present in the new DNA

Question 21

Predict experimental results in the Meselson and Stahl experiment if DNA replication was dispersive, conservative or semi-conservative.

Answer 21

Dispersive: If true, then the first generation of DNA N15 would be in the middle range (which did happen) but the other generations would always be in the range as all DNA copies would have N15 to weigh them down which was not the case
Conservative: If true, then after the first replication there would be a purely N15 DNA strand and a purely N14 DNA strand, but that was not the case, there was a middle range that had both together
Semi-Conservative: If the DNA replication was semi-conservative then after the first generation, all the DNA would be in the middle of N14 and N15, then more and more of the subsequent generations of the DNA would be only in the N14 weight area

Question 22

Use a genetic code table to determine the amino acid sequence coded for by a given antisense DNA sequence or an mRNA sequence.​

Answer 22

Notebook!

Question 23

Deduce the antisense DNA base sequence that was transcribed to produce a given mRNA sequence.​

Answer 23

Notebook! (antisense is just the other pairings of the mRNA sequence but with T and not U)

Question 24

Name of the bond between the phosphate group and the sugar in DNA

Answer 24

Phosphodiester bond