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DNA Replication

7.2

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7.2.1 State that DNA replication occurs in a 5-3 direction

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Replication proceeds in both directions from the origin and on both strands

this causes it to be continuous on the leading strand but discontinuous on the

lagging strand

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This is a very similar process in eukaryotes and prokaryotes.

In prokaryotes there is one origin of replication whereas eukaryotes there are

many (7.2.3).

Replication proceeds in both directions from the origin on both strands.

7.2.1 Notice

that replication

occurs in a

5-3 direction.

You tube too!

7.2.2 Explain the process of DNA replication in prokaryotes, including the role of

enzymes (helicase, DNA polymerase, RNA primase and DNA ligase), Okazaki

fragments and deoxynucleoside triphosphates.

http://www.freesciencelectures.com/video/dna-replication-process/http://www.freesciencelectures.com/video/dna-replication-process/http://207.207.4.198/pub/flash/24/menu.swf

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http://www.wiley.com/legacy/college/boyer/0470003790/animations/replication/replication.swf

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http://www.johnkyrk.com/DNAreplication.htmlhttp://www.mcb.harvard.edu/Losick/images/TromboneFINALd.swfhttp://www.wiley.com/legacy/college/boyer/0470003790http://www.stolaf.edu/people/giannini/flashanimat

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http://en.wikipedia.org/wiki/DNA_replication

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Instead of a nucleotide with a complementarybase adding to a new strand, a nucleosidetriphosphate does.

base

deoxyribose

tri-phosphate

DNA

Polymerase III

When the enzyme is released

two phosphates are removedfrom the nucleoside molecule.

This releases energy which

forms the bond between the

phosphate and the deoxyribose

of another nucleotide alreadyformed and in place along the

strand.

The hydrogen bonds between

the complementary base pair

then forms.

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Okazaki fragments

The lagging strand is builtin a discontinuous way.

(A series ofsections of

DNA strands built in a 5-3 way but on an original(lagging) strand which isin a 3-5 direction.)

These sections on the

lagging strand are calledOkazaki fragments.

DNA ligase binds thesefragments together.

T d ll t d t it it ti i f ti (DNA) t

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Click to access movieClick to access movie

To reproduce, a cell must copy and transmit its genetic information (DNA) to

all of its progeny.

To do so, DNA replicates, following the process ofsemiconservative

replication. Each strand of the original molecule acts as a template for the

synthesis of a new complementary DNA molecule.

The two strands of the double helix are first separated by enzymes. With theassistance of other enzymes, spare parts available inside the cell are bound

to the individual strands following the rules ofcomplementary base pairing:

adenine (A) to thymine (T) and guanine (G) to cytosine (C).

Two strands of DNA are obtained from one, having produced two daughter

molecules which are identical to one another and to the parent molecule.

http://www.accessexcellence.org/RC/VL/GG/possible.htmlhttp://www.accessexcellence.org/RC/VL/GG/possible.htmlhttp://www.accessexcellence.org/RC/VL/GG/collaboration.htmlhttp://www.accessexcellence.org/RC/VL/GG/structure.htmlhttp://www.accessexcellence.org/RC/VL/GG/structure.htmlhttp://www.accessexcellence.org/RC/VL/GG/collaboration.htmlhttp://www.accessexcellence.org/RC/VL/GG/possible.htmlhttp://www.accessexcellence.org/RC/VL/GG/possible.htmlhttp://207.207.4.198/pub/flash/24/menu.swfhttp://www.ncc.gmu.edu/dna/repanim.htm

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DNA vs RNAWhat is the differences between RNA and DNA?

DNA RNA

Deoxyribose Ribose

Two strands in double

helix

One strand only

Thymine Uracil

Longer Usually shorter

Occurs in nucleus of

eukaryotic cells

Occurs in and outside

nucleus

DNA mRNA, rRNA, tRNA

7 2 3 St t th t DNA li ti i i iti t d t i t i k ti

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7.2.3 State that DNA replication is initiated at many points in eukaryotic

chromosomes.