2.7 DNA Replication

Which scientists proved that DNA replication is semi-conservative?

• Hershey and Chase

• Watson and Crick

• Meselson and Stahl

• Franklin and Wilkins

Starting with ¹⁵N¹⁵N (heavy) DNA, and after one generation in the ¹⁴N medium, Escherichia coli cells will contain

• all ¹⁵N¹⁴N (hybrid) DNA.

• half ¹⁵N¹⁵N DNA (heavy) and half ¹⁴N¹⁴N DNA (light).

• half ¹⁴N¹⁴N (light) DNA and half ¹⁵N¹⁴N (hybrid) DNA.

• all ¹⁴N¹⁴N (light) DNA.

Replication proceeds in a ____ to _____ direction.

• 3' to 5'
• 3' to 3'
• 5' to 3'
• 5' to 5'

DNA replication results in

• 2 completely new DNA molecules
• 2 DNA molecules that each contain a strand of the original DNA molecule
• 1 new DNA molecule and 1 original DNA molecule
• 2 DNA molecules, each with original and new parts of DNA interspersed

The enzyme ________ unwinds and unzips the DNA double helix.

• DNA polymerase

• Helicase

• DNA ligase

• Topoisomerase

This enzyme is capable of breaking Hydrogen bonds found between the bases of DNA

• Topoisomerase

• DNA Helicase

• DNA Polymerase

• Exonuclease

What is the backbone of DNA made of?

• Nitrogen bases
• Amino acids
• Double H
• Sugar & Phosphate

Meselson and Stahl investigated DNA replication by first feeding bacteria with bases containing 15N (heavy), and then with bases containing 14N (light). The results are shown in the photographs.

From this information, what would be the composition of the DNA in generation 3?

• There will be a single 14N band.

• There will be a single 15N band and a single 14N band.

• There will be a darker 14N band and a lighter hybrid band.

• There will be a single 15N band, a single hybrid band and a single 14N band.

A short sequence of nucleotides reads GGACAGAGCGCAGACGA. In which type of molecule could this sequence be found?

• DNA molecule only

• RNA molecule only

• Both in a DNA and an RNA molecule

• In double-stranded DNA only

For which discovery about DNA do Watson and Crick receive credit?

• DNA is the molecule that genes are made of.

• The amount of adenine equals the amount of thymine in an organism.

• Phosphate–pentose bonding along the nucleotide backbone is covalent.

• The shape of DNA is a double helix.