Lecture #21: DNA Structure

Question 1

Where is genetic info located?

Answer 1

Nucleus

Question 2

How to clone?

Cloning process

Answer 2

Nucleus is transfered from frog species A to frog species B (nucleus is already removed)

- Develops into an individual

Question 3

What is cloning? Cloning in plants?

Cloning

Answer 3

produce an individual from a single cell

Cloning in plants:
- take a single phloem cell from carrot
- grow in a medium of coconut milk
- produce root and shoot (vegetative propagation)

Question 4

Cloning in animals?

Animals (Dolly the Sheep)

Answer 4

Starts with udder cell
1. starve the cell (to stop/slow function)
2. Remove the nucleus and transported nucleus into cytoplasm of a zygote (nucleus removed)
3. shock the cell (initiates cell division)
4. Grow in petri dish for 16 days
5. implant into womb of surrogate ewe (female sheep)
- 1 clone (dolly)

Question 5

What are chromosomes? History of chromosomes?

Chromosomes

Answer 5

DNA and Proteins
- Early 1900s - Chromosomal theory of inheritance
- Hershey-chase

Question 6

What did they discover?

Hershey-Chase

Answer 6

1. Grew phages with radioactive sulfur (label protein as “hot”)
2. Grew phages with radioactive phosphorus (label DNA as “hot”)
3. Let phages infect bacteria
4. Shake in blender to remove viral coat (Collected the debris (viral coat))

Results:
- infected bacteria (from protein phages) was NOT hot
debris pellet was hot
- infected bacteria (from DNA phages) WAS hot
debris pellet was NOT hot

Question 7

What do they believe/do?

Modelers

Answer 7

• produce theory
• deductive reasoning (general –> specific)

Question 8

What do they believe/do?

Empiricists

Answer 8

• collect facts, did experiments with real-world material
• inductive reasoning (specific –> general)

Question 9

what did they know? how did they build DNA model?

Watson + Crick (1953)

Answer 9

What they knew:
1. number of adenine = number of thymine
- number of cytosine = number of guanine
2. Model should suggest replication
3. ATGC bases were hydrophobic
4. Lots of phosphate groups + sugar rings

Won nobel prize in 1962

Question 10

Rosalind Franklin + Maurine Wilkens

Answer 10

DNA X-Ray crystallography
- DNA was helix
- Diameter of DNA = 2 nanometers (2 x10-9 nm)
- Pitch of DNA = 3.4 nm

Pitch = distance between each spiral in DNA

Antiparallel = parallel but in different directions