DNA as the genetic material 1

Question 1

What is genetic drift

Answer 1

The change in the frequency of alleles over time in a population due to random sampling of organisms

Question 2

Describe the evolution of aging

Answer 2

Disposable soma: ageing is the progressive accumulation of unrepaired faults and damage.
According to the theory of antagonistic pleiotropy, there is a selection for genes that will help the ability to reproduce regardless of whether or not they have detrimental effects in the future.

Question 3

What is transformation?

Answer 3

Transformation is the ability of organisms to take up “Free” DNA from the external environment

Question 4

Describe an experiment that was used to explain transformation

Answer 4

The “Mice” experiment
Pneumoniae causes lethal infections in mice.
S -> smooth, polysaccharide capsule, lethal
R -> rough, no capsule, non lethal infections
S heated and denatured, injected into mice, no death
R injected into mice with denatured S, still death.
The R cells, not normally lethal, have turned into S cells.

Question 5

Describe the stability of RNA in comparison to DNA

Answer 5

RNA is more unstable than DNA. this is because of the -OH group at the 2’ position in RNA. it limits the range of secondary structures RNA can adopt, meaning that it is more susceptible to degredation.

Question 6

Describe DNA’s secondary structure

Answer 6

• double stranded helix
• polynucleotide chains around same axis
• held together by hydrogen bonds between bases

Question 7

What is the hyperchromic effect?

Answer 7

• Heat denatures dsDNA into ssDNA
• the process of this denaturation is called the helix coil transition.
• during the helix coil transition, there is an increase in absorbance of UV light
• this explains why ssDNA have higher absorbance than dsDNA

Question 8

Describe factors that have an effect on renaturation rate

Answer 8

• ssDNA can renature into dsDNA under certain parameters. However, this is effected by certain factors.
  1) nature of the sample - more complex DNA will take longer to anneal because it’s harder to find the matching fragments
  2) renaturation temperature - if the DNA is heated to Tm and rapidly cooled to 4 degrees, then it will remain denatured.
  3) fragment size - longer DNA fragments will take longer to anneal than shorter DNA fragments