Chapter 6

replication is _____________

bidirectional

first step of initiator proteins: pull apart the 2 strands of DNA by breaking the _________ bonds between _____________ bases, which opens up a short stretch of DNA, which exposes the bases of the _________ strands. this attracts a second set of proteins that start replication of DNA

hydrogen bonds; complementary bases; single;

each product of DNA replication consists of: (2 things)

- 1 conserved strand - 1 newly synthesized stand

Figure 6-12: at a replication fork, the two newly synthesized DNA strands are of opposite polarities

- bottom inside 5' → 3' strand is leading strand - top inside 5' → 3' strand is lagging strand

at each origin, there are ____ replications forks that are moving away from each other in OPPOSITE directions as replication proceeds

2

one double helix is replicated to form _____ identical double helices

2 identical double helices

adds nucleotides at ___ _______ of a _________ DNA strand using old (parental) strand as a template

3' end; growing

DNA polymerase has a _________ exonuclease activity

3'→5'

**DNA is only synthesized in the ___________ direction which means we are always adding/growing to the 3' end. CAN NOT add nucleotide to a 5' end of a growing strand. the 2 new DNA strands are constructed in different ways.

5' → 3'

Leading strand = DNA is synthesized continuously from the ________ end

5' → 3'

Replication forks

Y shaped junctions in the DNA as it is being replication

The replication fork is ____________

asymmetrical

after adding a nucleotide, DNA polymerase stays __________ to chain

attached

at lagging strand, DNA polymerase is moving ___________ from the fork (back stitching)

backwards

each strand of DNA contains a sequence of nucleotides that is _________________ to the nucleotide sequence of the partner strand

complementary

Lagging strand = DNA is synthesized ____________ in separate, small pieces call okazaki fragements which are synthesized 5' → 3' . BUT overall, on lagging strand, the DNA is growing in the ________ direction

discontinuously; 3' → 5' >strand is growing in opposite direction because of the way the fork is moving

DNA polymerase

enzyme that catalyzes DNA replication

DNA Polymerase

enzyme that synthesizes DNA

in DNA polymerase, can only add nucleotides to a ___________ DNA strand; can't start a new strand from scratch

growing

The replication fork is asymmetrical. One DNA strand is _________ ___________ at 3' end while the other strand is growing overall at its 5' end

growing overall

after adding a nucleotide, DNA polymerase checks to make sure corrected nucleotide was added. - If correct it...... - If incorrect.....

if correct it keeps going and DNA polymerase adds next nucleotide if incorrect, DNA polypeptide removes incorrect nucleotide by cutting the bond, and then adds the correct nucleotide

the process of DNA replication beings when these proteins, called "________ _________", bind to the origin

initiator proteins

original DNA strands remain __________ _________ ______________

intact through generations

DNA polymerase catalyzes formation of ______________ bonds between ____ ____ of last nucleotide in strand with the ____ ________ of the incoming nucleotide

phosphdiester; 3' OH; 5' phosphate

DNA polymerase is self-correcting and has a ______________ activity. it detects its own errors

proofreading

origin contains a particular sequences of nucleotides and is recognized by a set of __________ that bind to the nucleotide sequence at origin

proteins

DNA replication begins at __________ ___________

replication origins

DNA Replication is ______-conservative

semi-conservative

bacterial cells = ________ origin on a single circular chromosome

single

each strand can act as a ___________ for the synthesis of a new complementary strand

template (mold)

Figure 6-15: DNA polymerase contains separate sites for DNA synthesis and proofreading

the diagrams are based on the structure of an E. coli DNA polymerase molecule, as determined by X-ray crystallography. DNA polymerase is shown with the replicating DNA molecule and the polymerase in the polymerizing mode (left) and in the proofreading mode (right). the catalytic sites for the polymerization activity (p) and error-correcting proofreading activity (e) are indicated. When the polymerase adds an incorrect nucleotide, the newly synthesized DNA strand (red) transiently unpairs from the template strand (orange), and its growing 3ʹ end moves into the errorcorrecting catalytic site (e) to be removed.

at the forks, DNA is ________ as the forks move

unzipped

human genome = ________ origins that are spread out over the set of chromosomes

~10,000