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37 Cards in this Set

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Conservative Replication

- G1: 2 bands


- G2: 2 bands


- one daughter has 2 old strands


- the others have 2 new strands

Semiconservative Replication

- G1: 1 mixed band


- G2: 1 pure band above 1 mixed band


- two daughters have one new and one old


- two daughters have two new strands

Dispersive Replication

- G1: one mixed band


- G2: one mixed band (3:1)


- all daughters have mixed bands of new and old

Replication in prokaryotes

- begins at a point, replicates bidirectionally simultaneously, and ends at the terminus

What is referred to as Theta (ø)
- the replicating chromosome
Reverse Transcriptase
- RNA dependent DNA polymerase
RNA Replicase
- RNA dependent RNA polymerase
DNA Transcriptase
- DNA dependent RNA polymerase
DNA Replicase
- DNA dependent DNA polymerase
Template Strand

- 3' to 5' direction


- non coding or antisense strand

Non-Template Strand

- 5' to 3' direction


- coding or sense strand

__(1)__ is upstream and __(2)__ is downstream

(1) 5'


(2) 3'

DNA Polymerases (in general)

- can only elongate a strand using an RNA primer


- can only attach nucleotides in 5' to 3' direction

DNA Polymerase I

- essential (secondary) role in replication


- removes RNA primers ad fills gaps with DNA


- 5' to 3' polymerase activity


- 3' to 5' exonuclease activity (removes errors)


- 5' to 3' exonuclease activity (fills gaps between Okazaki fragments with DNA)

DNA Polymerase II

- exclusively repairs DNA


- 5' to 3' polymerase activity


- 3' to 5' exonuclease activity

DNA Polymerase III

- major replication enzyme in both strands


- 5' to 3' polymerase activity


- 3' to 5' exonuclease activity

DNA-A Protein (in Bacteria)
- binds to DNA-A boxes within the origin to initiate DNA replication
DNA-B Protein (in Bacteria)

- helicase


- separates double stranded DNA (dsDNA) by disrupting the H bonds


- uses ATP

DNA-C Protein (in Bacteria)
- aids DNA-A in recruitment of DNA helices (DNA-B) to the origin to initiate the complex
oriC (in Bacteria)
- wraps around DNA-A monomers
Topoisomerase

- gyrase


- removes positive supercoiling ahead of the replication fork


- releases coil stress caused by replication


- allows for unchaining of DNA (decatenation)

What is the order of DNA replication in bacteria?

(1) primase


(2) DNA Pol III


(3) DNA-A


(4) DNA-B (helicase)


(5) Single Strand Binding Protiens (SSBP)


(6) DNA ligase

Initiation

- begins at origin of repliction


- helicase unwinds DNA


- SSBP bind to single strands


- DNA pol III engages the separated portion

Elongation

- leading strand: RNA primer is placed (primase) then replication proceeds continuously


- lagging strand: multiple primers are placed and Okazaki fragments are formed (semi-discontinuous)


- strands are proof read then RNA primers are replaced (DNA pol I)

Primosome

- helicase + primase

Replisome
DNA Pol III + primosome
RNA Primers

- 5' end is closest to replication fork


- enzymatically removed and replaced with correct DNA nucleotides

DNA Ligase

- seals gaps with phosphodiester bonds between adjacent 5'-P and 3'-OH groups


- covalently attaches adjacent Okazaki fragments

Termination

- theta replication finishes with Y junction halting replication at mid point between strands


- ter site contains termination sequences which terminate replication when bound by tus

Tus
- binds to ter sequences and prevents advancement of replication fork

Decatenation
- unlinking of chains
DNA Replication (in general)

- has multiple origins of replication


- is bidirectional

Replication in Telomeres
- telomeric DNA sequences are added to the ends of eukaryotic chromosomes by telomerase
Telomerase

- active in germ cells and in bacteria


- inactive in somatic cells


- causes internal time clock

Progerias
- disorders dealing with telomere length and aging in humans

Hutchinson-Gilford Syndrome
- aging symptoms begin immediately after birth (severe)
Werner Syndrome
- aging symptoms begin in teenage years (mild)