Flashcards in Lecture 4 Deck (44):
The entire genetic complement of an
organism; includes its genes and nucleotide sequences
usually ds, closed circular DNA
Base Pairs of nucleic acids
G-C DNA and RNA
Explain DNA Replication
Polymerization process that requires monomers and energy
What does it mean to be SEMICONSERVATIVE in terms of DNA replication?
New molecule is composed of one original and one daughter strand
What proteins are required for replication complex?
SSDNA binding protein
Explain initial processes in DNA Replication
Enzyme called TOPOISOMERASE is located at the position of the blue circle during DNA replication
What is the function of enzyme called TOPOISOMERASE?
It removes the helical stress that would accumulate for the unwinding of the two DNA strands
type of TOPOISOMERASE, target for the quinoline antibiotics
How does the DNA Replication Start ?
DNA polymerase adds 5' nucleotides to free 3' hydroxyl groups
All chains grow only in 5' to 3' direction
Why does the new strand of DNa need to be synthesized differently?
Because two parental strands of DNA are antiparallel
How is Leading strand synthesized ?
How is Lagging strand synthesized ?
What is the replicative DNA polymerase in E. coli?
DNA polymerase III
two enzymes are needed one for each strand
What is RNA primase?
Special form of RNA polymerase
Begins chains for synthesis of both the leading and the lagging strands
What does the Lagging strand consists of ?
100-1000 base long
What is the function of DNA Polymerase I ?
Repair enzyme, causes Okazaki fragment to lose their RNA beginning nucleotides
How is RNA primary made?
it is made by PRIMASE a special form of RNA Polymerase
Define OKAZAKI FRAGMETNS
RNA primer and covalently attached deoxyribonucleotides
What is the function of repair enzyme?
A repair enzyme removes RNA primer from okazaki fragments and fills the space with DNA
process called NICK TRANSLATION
What is the function of DNA ligase?
it seals the sugar-phosphate backbone
What is the error for Polymerization?
1 mistake for every 10^4
Wat is the advantage of proof reading?
it reduces the error to 1 mistake for 10^7
What is the function of RESTRICTION MODIFICATION SYSTEM?
The restriction modification system (RM system) is found in bacteria and other prokaryotic organisms, and provides a defense against foreign DNA, such as that borne by bacteriophages.
Transcription is the first step of gene expression, in which a particular segment of DNA is copied into RNA (especially mRNA) by the enzyme RNA polymerase.
Difference between RNA and DNA Polymerase
RNA polymerase does not require 3'-Oh primer to Begin Transcription
does not require helicase
it is SLOWER than DNA polymerase
more errors in RNA
How is Transcription controlled in Bacteria?
only 75% of the genes are expressed at all times
other only used when cells need them
What are different kinds of Operons?
Inducible- must be activated by inducers
Repressible- transcribe continually until deactivated by repressors
The difference between Bacteria and Eukaryotes translation initiation?
In bacteria the 16S rRNA of small ribosomal subunit pairs with the Shine- Dalgarno sequences
Define Formylated MEt
first amino acid bounded to a specific initiator TRNA
all bacterial proteins begin with f-Met at their amino terminus
Define Shine-Dalgarno sequence
The Shine-Dalgarno (SD) sequence is a ribosomal binding site in bacterial and archaeal messenger RNA, generally located around 8 bases upstream of the start codon AUG. The RNA sequence helps recruit the ribosome to the messenger RNA (mRNA) to initiate protein synthesis by aligning the ribosome with the start codon.
When does the Termination occurs?
when a stop codon occupies the A site and a protein release factor RF causes peptide transferase to release the growing polypeptide chain from the tRNA in the P site
What is a Riboswitch?`
a regulatory segment of a RNA that binds a small molecule resulting in a change in production of the proteins encoded by the mRNA
where are riboswitches locate?
in the 5' UTR of mRNA
How are riboswitches build?
Aptamer-- binds the small regulatory molecule
The expression platform- regulates gene expression by changing its structure in response to changes in the aptamer
Why Bacterial Riboswitches are important?
Provide some support for the RNA
They can function as a target for antibiotics
change in the nucleotide base sequence of a genome
Types of mutation
Silent--- one codon changes to another-same amino acid
Missense--chagne codon for another amino acid
Nonsense-- change codon to stop codon
Define Virulent (Lytic) Phage
Phage that always causes death of their bacteria host via lysis of the bacteria cell
Nonlytic Filamentous Phage
Phage that are released from their bacterial host by "budding" from the living bacterial cell
Vertical Gene Transfer
Organisms replicate their genomes and provide copies to descendants
Horizontal Gene Transfer
DNA from outside of the cell contributes part of genome to recipient cell
Transformation-- naked DNA from solution
Transduction-- bacterial DNA in a virus
Conjugation--- sharing of DNA between two bacteria
Segments of DNA that move from one location to another i the same or different molecules