BISC 1111 - DNA Replication

Who created semi conservative model?

Watson and Crick

Semi-conservative model

when a double helix replicates, each daughter molecule will have one old strand and one newly made strand

What are the competitors of the semi-conservative model

Conservative & dispersive model

What is the conservative model of DNA replication?

Two parental strands reassociate after acting as templates for new strands.

What happens to the parental double helix in the conservative model?

It is restored after replication.

Dispersive model

bits and pieces of each strand have old and new pieces of DNA

Origins of replication

Site where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides.

replication fork

Where the two DNA strands separate and form a "bubble"

Helicases

enzymes that untwist the double helix at the replication forks

Topoisomerase

corrects "overwinding" ahead of replication forks by breaking, swiveling, and rejoining DNA strands

Single-stranded binding proteins

bind to and stabilize single-stranded DNA

Primase

synthesizes RNA primer

Primers

starting point for DNA synthesis, short structures of nucleotides

DNA polymerase

Adds nucleotides to the primer

Primer is how long??

5-10 nucleotides

New DNA strands start from which end

3' end of RNA primer

DNA polymerase synthesizes where?

Replication fork

DNA polymerase require what to synthesize?

primer & template strand

Nucleoside triphosphate

Nucleotide and growing DNA strand

dATP supplies what?

Adenine

dATP has what giving it it's "d"

deoxyribose

How do you lose a pyrophosphate

Monomer coupled with dehydration reaction

What is a pyrophosphate

it is two phosphates joined together

(Pi)… result of monomer + dehydration reaction

DNA strands are made in what direction

5' to 3'

Which strand is headed towards growing replication fork

Leading strand

Which strand has to be synthesized by polymerase in the opposite direction of the developing replication fork

Lagging strand

How is the lagging strand synthesized

as fragments

What are Okazaki fragments?

Small fragments of DNA produced on the lagging strand during DNA replication.

What enzyme joins Okazaki fragments?

DNA ligase

What is the purpose of Okazaki fragments in DNA replication?

To form a complete strand on the lagging strand.

DNA replication machine

proteins that participate in DNA replication form a large complex

What functions does DNA polymerase perform

reeling in parental DNA, extruding daughter DNA cells, proofreading, and replacing

Mistmatch repair

Repair enzymes replace incorrectly paired nucleotides

Nucleotide excision repair

Nuclease cuts out and replaces damaged segments of DNA

Examples of how DNA segments can be damaged

UV rays, harmful physical or chemical agents, or spontaneous changes

Where does genetic variation come from

Mutations in genetic sequence that bypass proofreading being passed down to offspring

For _ ____, replication machinery not complete the ___ end of daughter DNA strands

Linear DNA, 5'

Why is completing ends not a problem for prokaryotes?

Because most prokaryotic DNA is circular

Telomeres

postpone erosion of genes near ends of DNA molecules

Telomerase

catalyzes the lengthening of telomeres in germ cells

Bacterial chromosomes have ____ __ DNA, with _ amounts of protein

double stranded, small

Eukaryotic chromosomes have ____ DNA with _____ amounts of protein

linear, large

Histones

protein molecules around which DNA is tightly coiled in chromatin

Unfolded chromosomes = ???

Strings of nucleosome beads

Nucleosome

DNA wound twice around 8 histone proteins

Histone tail

extend from nucleosome and participates and in gene expression

Euchromatin

loosely packed chromatin

Heterochromatin

highly condensed chromatin

Where is heterochromatin found?

centromeres and telomeres during interphase