BioChem 2.7 DNA replication, transcription, and translation Flashcards
Is DNA replication conservative, semi-conservative or dispersive?
DNA replication is semiconservative. One strand will form from the original DNA strands. One strand will be newly synthesized.
Outline the protocol of Meselson and Stahl’s DNA replication experiments
Meselson and Stahl grew an E.Coli bacteria in a medium containing N15 Nitrogen atoms. After several generations all of the bacteria contained heavy DNA with two strands made from N15.
Then the E.Coli bacteria was transferred into a medium containing N14 nitrogen
Scientists allowed bacteria to complete 1 cell division by binary fission. They then took samples of the cells and tested the DNA in a centrifuge to measure its weight.
The bacteria then was allowed to complete several more replications by binary fission. Each time DNA was taken and measured in a centrifuge.
What can we conclude from Meselson and Stahl’s experiment?
From Melson and Stahl’s we can deduct that DNA replication is semi conservative as there is as DNA is always semi-transferred and semi conserved into the new generation.
What is the significance of the complementary base pairing rules to determine
DNA polymerase uses the complementary base pairing rules to determine the sequence of nucleotides as it builds a new strand of DNA. This ensures that the two daughter cells produced by mitosis are genetically identical
What is Taq polymerase?
Taq polymerase is a thermo-stable DNA polymerase enzyme.
This is enzyme is found from the heat loving bacteria, thus does not denature at extreme temperatures.
What does Taq polymerase do?
Taq polymerase performs the same role as DNA polymerase by producing several copies of of DNA during polymerase chain reaction. In order to artificially replicate human DNA.
What is the relationship between one gene and one polypeptide?
One gene holds information to make one polypeptide. (A gene is a section of the DNA)
Outline the process of transcription.
Process takes place inside the nucleus
- RNA polymerase will attach it self to the promoter site of the DNA.
- RNA polymerase unwinds the DNA by breaking hydrogen bonds. This creates a transcription bubble.
- RNA polymerase will build a new strand using complementary base pairing rules to pair RNA nucleotides along the anti sense strand.
- RNA polymerase reaches terminator where transcription is completed.
- RNA polymerase breaks away from DNA
- DNA double helix rewinds and mRNA is released
What are the three types of RNA?
mRNA (messenger = transcription)
tRNA (transfer = translation)
rRNA (ribosome = translation)
Outline the process of translation. (SL)
- Small ribosome sub-unit attaches itself to mRNA strand.
- mRNA is made of codons which is a sequence of 3 consecutive RNA bases. tRNA has anti codons which is also made of 3 consecutive RNA bases. A tRNA molecule always corresponds to a specific amino acid.
- Ribosomes will read the codons on the mRNA and using complementary base pairing rules, pair appropriate tRNA molecules.
- The ribosome works its way along the mRNA in direction of 5’ to 3’. Until it finished building the polypeptide chain.
Where does translation occur?
In a cell’s cytoplasm
When does translation occur in the cell cycle?
G1 and G2 Phase
Why does translation happen?
Translation happens in order to make polypeptides for protein synthesis.
What is the role of a ribosome?
The role of a ribosome is to read the base sequence of the mRNA and use this information to build a polypeptide.
What is the role of mRNA?
The role of mRNA is to hold genetic information from the nucleus to the ribosome.
