Chapter 12 Vocab Flashcards
One property of the genetic material necessary for its function is the ability to:
replicate (reproduce) itself.
___________________ of DNA structure suggested a possible mechanism for replication of DNA molecules.
The Watson-Crick model
The nature of ______ _______ meant that if the two strands of a DNA molecule were separated, they could each serve as a template for the creation of a complementary strand by bringing in individual nucleotides to base pair with their complementary base on the template, and joining the new nucleotides together.
base pairing
Each DNA molecule after replication would consist of :
one of the original strands plus one newly synthesized strand.
Each DNA molecule after replication would consist of one of the original strands plus one newly synthesized strand is know as the:
semiconservative model of DNA replication.
___________ ___________ proposed that after replication, one DNA molecule consists entirely of newly synthesized DNA whereas the other molecule is entirely original DNA.
Conservative replication
____________ ___________ suggested that each DNA molecule after replication might consist of segments of new and old DNA interspersed.
Dispersive replication
What was Meselson and Stahl’s Experiment?
• First, they grew bacteria for many generations in a growth
medium containing 15N.
• This is a heavy isotope of nitrogen (in contrast to the normal isotope, 14N), which over many generations would be incorporated into all nitrogen-containing molecules of the cells, including DNA.
• DNA isolated from these cells could be distinguished from normal DNA because it would have a higher density (15N).
• A centrifuge tube is filled with a heavy salt solution and DNA fragments.
• It is then spun in a centrifuge at high speeds for several days.
• A density gradient develops within the tube. DNA will move to where its own density matches that of salt.
• Light DNA (w/14N) will remain closer to the top.
• Heavy DNA (w/15N) will move toward the bottom.
What was the outcome of Meselson and Stahl’s experiment?
- If semiconservative replication occurred, then each DNA molecule after replication would contain heavy nitrogen and light nitrogen, and would therefore have a density intermediate between the two.
- Conservative replication would produce one DNA molecule containing heavy nitrogen and one molecule containing light nitrogen, so there would be two different densities.
- Dispersive replication would produce a single intermediate density, just like semiconservative.
What are characteristics of semi-conservative replication?
- A more modern technique using a dye called bromodeoxyuridine can be used to show semiconservative replication as well.
- In addition, crossovers are easy to see.
- Hybrid chromatids are called: Harlequin chromosomes
What is the mode of replication for bacteria?
have a single specific origin of replication; in other words, bacterial replication begins at the same spot on the chromosome every time.
Theta replication is:
When replication proceeds around the circle in both directions from the origin; i.e., replication is bidirectional.
Replication that takes place in some viruses and in the F factor of E. coli and that is initiated by a break in one of the nucleotide strands is known as _____________ replication.
Rolling-circle replication
How does rolling-circle replication work?
- -DNA synthesis begins at the 3’ end of the broken strand
- -the inner strand is used as a template
- -the 5’ end of the broken strand is displaced
- -Cleavage releases a single-stranded linear DNA and a double stranded circular DNA.
- -the linear DNA may circularize and serve as a template for synthesis of a complementary strand.
The products of rolling-circle replication are:
Multiple circular DNA molecules
