AP BIO Unit 6.1 & 6.2

Prokaryotic DNA

Single, circular, double- stranded DNA that is associated with a small amount of protein

Eukaryotic DNA

Linear DNA associated with a large amount of protein

between sugar phosphate backbone

covalent bonds

between nucleotides

hydrogen bonds

Directionality of DNA

5’ phosphate end to 3’ hydroxyl end

What does DNA replication ensure?

the continuity of hereditary info

Purines

2 rings (Adenine and Guanine)

Pyrimidines

1 ring (Cytosine, Uracil, Thymine)

Conservative (1st round)

1 parent and 1 new nucleotide

Conservative (2nd round)

1 parent and 3 new nucleotides

Semiconservative(1st round)

2 new and old nucleotides

Semiconservative (2nd round)

2 new and old nucleotides, 2 new nucleotides

Dispersive (1st round)

2 integrated new and old nucleotides

Dispersive (2nd round)

4 integrated new and old nucleotides

Conservative (Band Version)

2 bands, 1 at top (N14) and 1 at bottom (N15)

Semiconservative (Band’s version)

1 middle(N14+N15) and 1 top(N14)

Dispersive (Band’s version)

1 band in the middle (N14 mixed with N15)

Prokaryotes Origin of Replication #

1

Eukaryotes Origin of Replication #

more than 1

the nucleotides arrive as

nucleoside triphosphates (their own energy source for bonding)

When a DNA polymerase reads

2 phosphates are released to create a covalent bond

Topoisomerase

Relaxes the supercoil at the replication fork

Helicase

unwinds DNA strands

DNA polymerase

synthesizes new strands attaches to the 3’ end and builds strand in the 5’-3’ direction

ligase

joins DNA fragments on the lagging strand

Single-strand binding proteins

stabilize the unwound parental strands

primase

synthesizes RNA primers by using the parental DNA as a template

RNA primer

serves as starter for DNA polymerase, provides a 3’ OH end

Elongation of new DNA at replication fork

DNA polymerases add nucleotides to the 3’ end of growing strand

How are covalent bonds formed?

Dehydration synthesis (removes H2O)

Leading strand

One strand of DNA that will be replicated continuously

Lagging strand

Strand of DNA replicated in segments

Okazaki fragments

a series of fragments that the lagging strand synthesizes

Leading strand direction

Towards the replication fork

Lagging strand direction

Away from the replication fork

Phosphate terminus

5’ end

Hydroxyl Terminus

3’ end

Is DNA replication conservative, semi-conservative, or dispersive?

Semi-conservative

Direction for leading vs lagging strand

OPPOSITE DIRECTIONS!

Helicase function?

Creates fork and destroys hydrogen bonds

mutation in helicase

will not unzip and enzyme does not work

mutation in ligase

cannot join strands, will result in fragments

mutation in primase

helicase unzips DNA and nothing happens

mutation in topoisomerase

DNA becomes too twisted and replication cannot continue

mutation in DNA polymerase

DNA cannot be copied correctly or at all

mutation in single strand binding protein

the unwound DNA strands are not stabilized and reattach so it stops the replication