AP Bio 16.2 Reading Guide

The _______ states that each of the two daughter molecules produced in replication will have one old strand, from the parental molecule, and one newly made strand.

• conservation model

• antiparallel model

• semiconservative model

• dispersive model

Meselson and Stahl cultured bacteria for several generations in a medium containing nucleotide precursors labeled with a heavy isotope of nitrogen, ¹⁵N. They then transferred the bacteria to a medium with only ¹⁴N, a lighter isotope. A sample was taken after DNA replicated once. DNA from the bacteria was extracted and then centrifuged. The DNA was separated based on densities. Which of the following shows the results of centrifugation of the DNA after a single replication in the new medium (¹⁴N)

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The replication of a DNA molecule begins at particular sites called ______________________, short stretches of DNA having a specific sequence of nucleotides.

• origins of replication

• replication forks

• replication bubbles

• telomeres

• primers

If the new DNA strand is being built continuously toward the replication fork, that strand represents the ___

• lagging strand

• template strand

• coding strand

• leading strand

Okazaki fragments are ___

• found on the leading strand and built toward the replication fork

• found on the lagging strand and built toward the replication fork

• found on the leading strand and built away from the replication fork

• found on the lagging strand and built away from the replication fork

Helicase ____

• untwists and separates strands

• holds DNA strands apart

• synthesizes RNA primer

• adds DNA nucleotides to new strand

• relieves strain caused by unwinding

DNA polymerase III ___

• joins DNA fragments together

• removes RNA primer and replaces with DNA

• synthesizes RNA primer

• adds DNA nucleotides to new strand

• relieves strain caused by unwinding

Topoisomerase ___

• joins DNA fragments together

• removes RNA primer and replaces with DNA

• synthesizes RNA primer

• adds DNA nucleotides to new strand

• relieves strain caused by unwinding

Ligase___

• joins DNA fragments together

• removes RNA primer and replaces with DNA

• synthesizes RNA primer

• adds DNA nucleotides to new strand

• relieves strain caused by unwinding