EXAM 3 Review Flashcards
Describe Griffith Experiment
- S strain was injected in mice A and R strain was injected in mice B. Mice A died and Mice B lived
- S train was killed with heat and injected into mice. Mice lived
- Killed S strain and R strain was mixed and injected into mice. Mice died
Shows that R strain took genetic information of S strain, transformation into a pathogenic lethal strain.
Describe Avery, McLeod, and McCarty experiment and how that supports Griffith Experiment
They extracted fractions of of S-strain cells and showed that DNA was related to S strain while the other fractions were R strains, proving that DNA was the genetic material
Describe Meselson and Stahl experiment
Grew bacteria in the presence of isotopes of nitrogen – can be separated by centrifugation on cesium gradient
The results showed that the band size was between all light and all heavy. Then they separated the band, showing semiconservative
Why is the lagging strand replicated in patches and not continuous as leading strand?
Because DNA polymerase can only replicate 5’ to 3’
What are the enzymes required for synthesizing the lagging strands?
- Primase
- DNA polymerase
- Ribonuclease
- Repair Polymerase (DNA polymerase I)
- DNA ligase
What are the roles of the enzymes required for synthesizing the lagging strands
- Primase: Synthesize the primer for replication initiation
- DNA polymerase: Extend the okazaki fragment until it reaches the next primer
- Ribonuclease: Degrade the RNA primer
- Repair Polymerase (DNA Polymerase II): Replaces the RNA with DNA
- DNA ligase: Joins the fragment together
What are the proteins required for involved in DNA replication?
- Initiator protein
- DNA polymerase
- DNA primase
- Ribonuclease
- Repair Polymerase
- Ligase
- Helicase
- Single Stranded DNA binding protein
- Sliding Clamp
What are the roles of the proteins required for DNA replication?
- Initiator Protein: Helix open at replication origin
- DNA polymerase: synthesize DNA from 5’ to 3’
- DNA Primase: Synthesis of RNA primer
- Ribonuclease: Degrade RNA primer
- Repair Polymerase: Turns RNA into DNA
- Ligase: Joins the Okazaki fragments together
- DNA Helicase: Unzips DNA helix
- Sing Stranded DNA Binding Protein: Prevent double strands from joining after unzipping
- Sliding Clamp: keeps DNA polymerase attached to template and on lagging strand, releases when Okazaki fragment is completed
What is the role of telomerase in the cell? How would deletion of the telomerase gene affect rapidly dividing cells?
Telomerase synthesizes telomere and adds it to 3’ end of lagging strand and ensure the ends of the chromosomes are replicated by DNA polymerase.
If telomerase is not present, each time a cell divides, a part of the tip of the chromosome is lost. For rapidly dividing cells – this would mean losing genetic information which can lead to dysfunction
With regard to double stranded DNA break repair: compare homologous and non-homologous recombination. Which will results in a more accurate DNA repair?
Non homologous recombination is quickly connecting the broken strands together by having the nuclease cutting the broken ends so ligase can close it.
Homologous recombination is synthesizing the broken strand by using another strand as a template.
Homologous is more accurate because in non homologous, the nuclease cutting the broken end leads to loss of genetic information
Discuss the consequence of a cell in which mismatch repair is inactive
Accumulation of mutations which are transmitted to daughter cells, eventually – can lead to deleterious mutations and cell death or dysfunction (like cancer)
What are the key features of a eukaryotic mRNA
RNA processing – 5’ cap, polyA tail, RNA splicing; one protein coding gene per mRNA molecule
What happens if histone were to be acetylated?
Histone will have a less affinity for DNA.
The acetylation of histone cause it to be more negatively charged and because DNA is negatively charged, the affinity is less. This ease access to DNA promoting transcription.
What are the basic steps involved in ribosome assembly on a mRNA?
- Translation initiation factor and initiator RNA (MET) bind to small ribosomal subunit
- Ribosomal subunit binds to mRNA
- Ribosomal subunit moves along mRNA
- Translation initiator factor dissociates
- Larger ribosomal subunit binds and cap on the smaller ribosomal subunit
Explain what combinatorial control of transcription is.
A group of transcriptional regulators working together to regulate a gene
