DNA Replication and Recombination | Quizlet Import

What are the three models of DNA replication

- conservative
- dispersive
- semiconservative

conservative replication

dispersive replication

semiconservative replication

each strand serves as a template for a new strand during replication

describe the Meselson and Stahl experiment

-fill centrifuge with salt and DNA
- spin for days
- heavy/light DNA separate

theta replication

replication of circular chromosomes. resembles greek later theta

what is the product of theta replication

two circular DNA molecules

rolling circle replication

takes place in viruses and plasmids. circular DNA breaks and copies a strand starting with 3' end

what is the products of rolling circular replication

multiple circular DNA molecules

replicon

individual unit of replication. larger DNA molecules require more

linear eukaryotic replication

large linear chromosomes are too large to replicate quickly from a single origin. they have many origins

products of eukaryotic DNA replication

two linear molecules

understand difference between theta, rolling-circle, and linear eukaryotic replication models

what is required for replication

- template strand
- raw materials/substrates
- enzymes/proteins to read template and assemble substrates

what is the raw material that synthesizes DNA

dNTP (deoxyribonucleoside triphosphates).

how is dNTP attached to DNA

DNA polymerase

enzymes that synthesize DNA by adding nucleotides to 3' end

in which direction is DNA read and synthesized

read in 3' to 5' direction
SYNTHESIZED in 5' to 3' direction

okazaki fragments

short lengths of DNA produced by discontinuous replication

understand theta replication model

understand rolling-circle replication model

understand linear eukaryotic replication

how does initiation (start of replication) begin

1) initiator proteins bind to the origin of replication
2) this causes DNA to unwind
3) unwinding allows helices to attach

how does the unwinding process work

1) helicase unwinds DNA at replication fork
2) single-strand binding proteins prevent secondary strands from forming
3) DNA gyrase relieves strain

what do DNA polymerases require? what provides this?

- they require a nucleotide with a 3'-OH group
- primase synthesizes short stretches of RNA with a 3'-OH group

understand how primers operate

what is the function of DNA polymerase

elongate the polynucleotide strand. DNA polymerase III is the main workhorse of replication.

common features of all E. coli DNA polymerases

function of DNA polymerase III

adds nucleotides to primer

function of DNA polymerase I

replace RNA nucleotides of primer with DNA nucleotides

function of DNA ligase

seals the "nick" between 5' group in initial nucleotide and 3'-OH group of final nucleotide added by DNA polymerase I

understand components required for replication in bacterial cells

basic components of replication fork

- helicase
- single stranded binding proteins
- gyrase
- primase
- DNA polymerase

what adjustments does DNA make in order to replicate both strands at the same time

- lagging strand loops around by leading strand so they replicate simultaneously
- when lagging strand ends, it shifts to new position

what are two ways that errors are corrected

- proofreading
- mismatch repair

rules of replication

- always semiconservative
- begins at origins
- fast and accurate

what is unique to eukaryotic DNA replication

- multiple origins of replication
- linear chromosomes
- presence of histones and nucleosomes

what are autonomous replication sequences in eukaryotic DNA replication

these sequences can enable replication in any DNA sequence to which they are attached. contains A-T base pairs.

what are the two steps for initiation in eukaryotic DNA replication

1) origins are marked by replication licensing factor
2) replication machinery starts only at origins licensed by RLS
*after replication begins, replication licensing factor leaves so as not to begin again during that cell cycle

MCM complex

mini chromosome maintenance. DNA helicase unwinds DNA after binding of MCM to DNA

Geminin

prevents MCM from binding again and reinitiating. degraded at end of mitosis, allowing a relicensing of the origin.

what would happen if there were no special mechanisms to fill the gap after the removal of a primer

DNA replication would leave gaps

in DNA replication in eukaryotes, what fills the gap let by RNA primer

telomerase extends the DNA filling the gap