DNA Replication
What is the correct model of DNA replication
Semiconservative model
What is this model express and how is it correct?
Does prokaryotic replication follow this model?
Explain the degeneracy of the universal genetic code
Several different codons code for the same amino acid, and the entire 3rd nucleotide of a codon doesn't change the amino acid produced at all.
This creates robustness and a fail-safe system to prevent dangerous mutations from occurring more often.
What is a mutagen
agent, such as radiation or a chemical substance, which gives rise to genetic mutations
What structure in prokaryotes has structural genes organized together with the same regulatory gene and same regulatory region
Operon
What is included in the regulatory region?
What is an Hfr cell
Stands for High frequency of recombination
When the F plasmid integrates into the bacterial chromosome/genome.
Name 5 enzymes necessary for DNA replication and their function
Topoisomerase II
Helicase
RNA primase
DNA polymerase I and III
Exonuclease
DNA Ligase
What point mutation is the substitution of a single nucleotide resulting in an amino acid substitution
Missense
What are the other Point Mutations?
What mutagen leads to the formation of single-stranded (nick) and double-stranded breaks in the sugar phosphate backbone of DNA.
Ionizing radiation
What enzyme binds to the promoter and transcribes structural gene(s)
RNA Polymerase
Explain the 3 prokaryotic-specific mechanisms leading to horizontal gene transfer
Transformation = Cell takes up naked DNA from the environment as a plasmid or integrated into the host genome.
transduction = bacteriophage injects DNA that is a hybrid of viral DNA and previously infected host DNA.
Conjugation = DNA is transferred between cells through conjugation pilus forming a bridge, rolling circle replication transfers daughter DNA to the F- recipient cell becoming F+.
What is an F plasmid?
On what structure of DNA are nucleotides added onto, and how does this result into a leading and lagging strand
Nucleotides are added onto the 3'-OH group of DNA strands.
Since strands are antiparallel, the lagging strand has to polymerize 3' to 5' in short stretches called Okazaki fragments between RNA primers. The leading strand polymerizes daughter DNA from just one RNA primer through continuous synthesis.
what process is used to identify mutagenic and potentially carcinogenic chemicals.
Rat liver extract is mixed with possible mutagens and the number of reverse mutants capable of growing are compared to natural reversion mutants.
the Ames test
What are nucleoside analogs and how are they used to identify protiens
nucleoside analogs are alternative nitrogenous bases that are similar to or can be used instead of normal nucleotides.
EX: Thymine turning into 5-bromouracil binding with Guanine.
They are used to identify proteins by mutating the protein and observing what function was affected by the mutation.
When does CAP bind to the promoters of operons, stimulating an increase in RNA Polymerase activity
CAP binds the promoter in the presence of cAMP
During transcription the mRNA Complement is synthesized if what direction
5' to 3'
(same direction as daughter DNA during replicaiton)
How does rolling circle replication occur in the circular genome of bacterial cell
A 'nick' in dsDNA displaces a single strand. While the parent strand is polymerizing a complementary daughter strand with DNA polymerase III, the displaced parent strand is broken off and starts to synthesis its daughter strand.
An auxotrophic mutants can’t produce a nutrient vital for growth due to genetic mutations. As a result, these strains are unable to survive in media lacking that specific nutrient unless it is provided externally.
What process is used for the Identification of auxotrophs
Replica plating
Nonionizing radiation is a mutagen that occurs when UV light leads to the formation of what, introducing a frameshift or point mutation and stalling replication/transcription.
Thymine Dimers, covalently bonded Thymine molecules and a kink in the sugar phosphate backbone.
What are transposons
segments of DNA that can move from one location to another coded for transposase.
This is usually a problem and can disrupt transcription when a transposon is inserted inside of a gene.
What is the CCA, 3' end of a tRNA molecule called
Amino acid attachment site
On the leading strand's newly synthesized DNA molecule, Telomerase completes the chromosomal genome how
It adds DNA nucleotides to the parent strand so that a new RNA primer can be placed, and DNA polymerase can complete the genome.
How does age affect this process?
What are 2 mechanisms for repairing thymine dimers for bacteria, how do they work and what enzymes are involved
1. Nucleotide excision Repair = the thymine dimer is cut out of the strand of DNA and DNA polymerase I and ligase repair the strand with new nucleotides.
2. Photoreactivation = The enzyme photolyase in the presence of light will bind to the thymine dimer and break the covalent bond restoring the DNA strand.
What mutagen introduces atypical spacing between base pairs resulting in a frameshift mutation during replicaiton.
Acridine is an example
Intercalating agents
Repressors bind to the operator when tryptophan is plentiful, stopping the transcription of tryptophan biosynthesis.
The lac operon contains structural genes that break down lactose. Do the repressors bind to the operator in the absence or presence of lactose.
The repressor binds to the operator in the absence of lactose, stopping the production of genes that breakdown lactose
What structure in eukaryotic cells is a DNA sequence that promotes transcription.
It is made up of short DNA sequences called distal control elements where activators are bound interacting with mediator proteins and transcription factors.
Enhancer