Bacterial DNA Replication & Recombination Flashcards
What are the 3 mechanisms used to explain DNA replication?
- Conservative model
- Semiconservative model
- Dispersive model
Existing DNA acts as a ________ for the synthesis of new strands
Template
The __________ strand are the DNA strand that are used as a template to form the new DNA strand (which is called the daughter strand)
Parental
Chargaff’s rule
States A binds to T & G binds to C
Conservative model
Parental strands neanneal (produced)
Semiconservative (hybrid)
1 parental & 1 daughter strand produced
Dispersive
1 parental & daughter strand interspered
DNA replication is _________________
Semiconserative
Bacterial chromsomes contain a __________ origin of replication
Single
Origin of replication
Site on the bacterial chromsomes where DNA synthesis begins (only have one)
What are the requirments for bacterial replication?
- Origin of replication
- DNA polymerase
- Accessory enzymes & topoisomerase
The synthesis of new ___________ strand is initiated within the origin & proceeds in both directions (bidirectionslly) around the bacterial chromosome
Daughter
A replication fork
The site where the parental DNA strand have seperated & a new daughter strand is being formed
What are the 3 steps in bacterial DNA replication?
- Initiation
- Elongation
- Termination
Initiation
Bacteria has one origin of replication where it occurs bidirectionally
Origin of replication in E. Coli is called ___________
OriC (Origin of chromosomeal replication)
Bacterial DNA replication begins with the binding of __________ to sequence within the origin of replication known as DnaA boxes
DnaA proteins
The ____________ served as recognition sites for the binding of the DnaA proteins where they bind to the five DnaA boxes in oric to start DNA replication
DnaA boxes
Other DNA binding proteins bind to the DnaA boxes to seperate _________ rich regions since they have only 2 hydrogen bonds & G-C has 3 hydrogen bonds so they can easily seperate A-T
A-T regions
______________ unwinds the DNA strand by breaking the A-T bond which can cause a supercoling
DNA helicase
DNA replication occurs at the _____________
Replication fork
___________________ travels in front of the DNA helicase to release the supercoling
Topoisomerase 2
Single strand binding proteins
Bind to the strands of parental DNA & prevents them from reforming after being seperated by DNA helicase
After the bonds between the nucleotides are broken a ________ forms RNA primers where the RNA primers starts the DNA replication
Primase
The leading stramd
Made in the same direction as the replication fork is moving
The lagging strand
Short fragments in the opposite direction from the movement of the replication fork
The DNA helicase moves in the ___________ direction & seperates the DNA strand in two directiion creating 2 replication forks
5’ to 3’ direction
DNA polymerase
Synthesizes the new DNA strand (both the lagging & leading strand )
DNA polymerase travels unidirectional in the 3’ to 5’ direction but makes new strand in the _________ direction which is antiparallel to the template strand & forms a daughter strand DNA (or new DNA)
5’ to 3’ direction
A _____________ starts the replication process & DNA polymerase actually makes the new DNA strand
RNA primer
What are the 5 types of DNA polymerase?
- Polyermase 1
- Polyermase 2
- Polyermase 3
- Polyermase 4
- Polyermase 5
DNA polyermase ___ & _____ are used in normal DNA replication
1 & 3 (Mostly 3 though)
DNA polymerase ___, _____, & _____ used in DNA repair
2, 4, & 5
Polymerase is undirectional & only travels in the _____________ direction
5’ to 3’ direction
The synthesis of the leading strand is ___________ whereas the synthesis of the lagging strand is ___________ process where it repeatedely needs to start
Continous, discontinous
The lagging strands are known as what?
Okazaki Fragments
____________ degrades the primer & fills in the gaps between the lagging strand
Polymerase 1
_______ links the okazaki fragments together
Lingase
_____________ removes the RNA from okazaki fragments (nuclease activity) (Polymerase activity forming DNA nucleotides the daughter strand)
Polyermase 1
Each replication fork has a _______ & _______ strand
Leading & lagging strand
________________ removes the RNA primers & fills it with DNA nucleotides
Polyermase 1
Elongation
Leading & lagging strand elongate (due to polymerase 3)
___________ is more complex than bacterial DNA replication where the chromosomes are larger, linear, longer, & highly packed
Eukaryotic replication
__________ replication has multiple origin of replication (Initiation occurs at multiple origins of replication on linear eukaryotic chromosome)
Eukaryotic DNA replication
_________________ can’t replicate ends of DNA genetic material is lost, it makes a new DNA in the 5’ to 3’ direction but can’t start the replication process (Because no place for a primer to bind & polymerase needs a primer to start)
DNA polymerase
____________ are repetitive sequences at the end of chromosomes that are 3’ overhang
Telomers
_____________ enzyme replicates telomers to maintain the length of a chromosome, it has proteins & RNA where the RNA is complementary to telomerase sequence
Telomerase
____________ makes 6 new nucleotides on the RNA template & the new nucleotides make a bind site for the primase to make the RNA primer
Telomerase
___________ extends telomers
Telomerase
The ends of eukaryotic chromosomes are replicated by _________
Telomerase
___________ prevents chromosome shortening
Telomerase
__________ can cause stress which causes shorter telomeres (which is bad for our health)
Children