T2.7 Replication, Transcription and Translation Flashcards
Who discovered the evidence for semi-conservative replication?
Meselson and Stahl
What does semi-conservative mean
- Two strands seperate and they each serve as a template for the creation of the new strand
- The new DNA molecule is composed of an original strand and a newly synthesized strand
Structure of helicase
Globular protein composed of 6 polypeptide arranged in a donut shape
Function of helicase
Uses ATP to move along DNA and breaks hydrogen bonds between nitrogenous bases
Function of polymerase
Adds complimentary bases to the 3’ end of new growing strand
Which direction is the newly synthesized strand of DNA created?
5’ to 3’ direction
What is Polymerase chain reaction (PCR)
a method to amplify the production of any pieceof DNA by heating
What is Taq DNA Polymerase
The DNA Polymerase extracted from Thermua aquaticous, which is found in hot springs and lives at temps of 75 C
Why is Taq DNA Polymerase used in PCR
The polymerase, and other proteins, can resist denaturation at the temps needed to seperate DNA helix into single strands (95 C) that can be copied by the Taq DNA polymerase. This makes it so DNA can be made a lot faster than having helicase unwind the strand every time.
General concepts of Transcription
RNA Polmerase seperates DNA, adds complimetary nucleotides to form single strand of mRNA
DNA -> mRNA
Sense strand
DNA sequence that contains the protein coding sequences, and is not what is copied in transcription. It is opposite to the anti-sense strand.
Anti-sense strand
Acts as the template and has complementary base sequence to the mRNA. It is what mRNA binds to. Another name is the template strand
Outline of the process of translation
- Synthesis of polypeptide determined by the base seuence of mRNA molecule.
- mRNA code is translate from 5’ to 3’ end
- occurs at ribosome
mRNA -> polypeptide
Outline of the process of translation
- Synthesis of polypeptide determined by the base seuence of mRNA molecule.
- mRNA code is translate from 5’ to 3’ end
- occurs at ribosome
mRNA -> polypeptide
Structure of a ribosome
- large and small subunits
- composed of mostly rRNA and some proteins/enzymes
- picture
Codon
A sequence of 3 bases on the mRNA that codes for an amino acid
Degenerate code
Refers to codons that code for the same amino acid, ex serine (6 codons code for it)
3 components that work together to synthesize polypeptides by translation
1) mRNA’s sequence of codons that specifies the amino acid sequence
2) tRNA molecules’s anticoon of 3 bases that binds to the complementary codon on mRNA, which carries the corresponding amino acid
3) Ribosomes that act as the binding site for mRNA and tRNA, also catalyzes the assembly of polypeptide
Define Universal code
You can put in any gene into a cell, and it will still make the protein, meaning that the proteins always code for the same protein in every cell
How is the production of human insulin in bacteria an example of the universality of the genetic code
They put human genetic code into an e. coli bacteria, and the bacteria produced the exact same insulin it produced in the human.
What did Meselson and Stahl’s experiment demonstrate?
Figured out which possible outcome of DNA replication was right (semi-conservative)
Three possible outcomes based on Watson and Crick’s DNA model
Disperative: chunks itself into segments and each would be copied
Conservative: DNA would be wrapped around histone proteins and would duplicate
Semi-conservative
link to picture of them
What was the isotope Meselson and Stahl used
Nitrogen-15 (extra neutron)
Why did Meselson and Stahl use N-15
Nitrogen is an important part of the DNA structure, and it can be seperated from the regular DNA on the basis of density
Where the strands in the original DNA of the e-coli heavy or not heavy (N-14 or N-15)?
Heavy, N-15
After growing the E.coli in normal media for one round of replication what happened to the density of the DNA?
The DNA grew lighter.
What is the reason for the DNA to grow lighter after the first round of replication?
The DNA would split itself in the middle and used semi-conservation, so every DNA would have heavy and not heavy
What did they observe about the density of the DNA after the 2n round of replication?
The DNA was 50% light and 50% heavy nitrogen