Lecture 1 - The hereditary molecule

Question 1

when was the Griffith transformation experiment (GTE)

Answer 1

1928

Question 2

which bacteria was fatal to the mouse in the transformation experiment?

Answer 2

live smooth bacteria

Question 3

why was live smooth bacteria fatal to the mouse

Answer 3

it had a protective coating that made it harder to attack by the mouse’s immune system

Question 4

what effect did the heat killed smooth bacteria have on the mouse in the transformation experiment

Answer 4

no effect as the heat killed the bacteria

Question 5

what effect did live rough bacteria have on the mice in the GTE

Answer 5

no effect
-strain is non virulent

Question 6

what happened when both the heat-killed smooth bacteria and the live rough bacteria were inserted into the mouse in the GTE

Answer 6

it was fatal to the mice

Question 7

what did scientists conclude about the heat-killed smooth bacteria and the live rough bacteria in the GTE

Answer 7

something was being transferred from the heat-killed smooth strain (dead) to the rough bacteria (live) and made the strain become virulent (Transformation Principle)

Question 8

bacterial transformation

Answer 8

some type of critical material could be transferred between bacteria and help change it’s properties

Question 9

when was the Avery-McCarty-Macleod experiment

Answer 9

1943

Question 10

what did Avery-McCarty-Macleod do with the smooth infective bacteria

Answer 10

Broke down the bacteria and isolated (removed) the major molecules: RNA, proteins, DNA and also had a control

Question 11

what different enzymes Avery-McCarty-Macleod mix the extract with and hy

Answer 11

protease
RNase
DNAse
* this was done to isolate the major molecules
-if the mouse still died despite removing the component, it was clear that the bio molecule was not that transforming principle

Question 12

why were carbs and lipids not tested directly in the Avery-McCarty-Macleod experiment

Answer 12

they were removed as a process of elimination

Question 13

what happened when proteases were added in the Avery-McCarty-Macleod experiment

Answer 13

bacteria caused the mice to die (not the transforming element)

Question 14

what happened when RNAses were added to Avery-McCarty-Macleod experiment?

Answer 14

bacteria caused the mice to die

Question 15

what happened when DNAses were added to the Avery-McCarty-Macleod experiment?

Answer 15

mouse lived suggesting DNA was the transformative molecule (DNA is most likely responsible for killing the mouse)

Question 16

what is a bacteriophage?

Answer 16

-A virus- one of the simplest organisms
-A protein coat surrounding a nucleic acid core

Question 17

how do bacteriophages work?

Answer 17

-attach to outside of host cell, inject genetic material into the host and hijacks the internal working of the cell

-DNA from the bacteriophage causes the cell to produce identical copies of the original bacterial phage

The host cell then explodes releasing the new bacteriophages which go and attack other cells

Question 18

when was the Hershey and Chase experiment?

Answer 18

1952

Question 19

what did Hershey and chase inject the bacteriophage with?

Answer 19

labelled phosphorus 32 and sulphur 35

Question 20

what happened to the bacteriophages when centrifuged?

Answer 20

the bacterial cells were heavier and sunk to the bottom of the centrifuge(pellet) and the fluid and leftover phage formed the supernatant( at the top)

Question 21

what would it show if the pellet contained phosphorus?

Answer 21

DNA made it into the bacteria (this is what was found)

Question 22

what is the best way to label nucleic acids?

Answer 22

label the phosphate e.g. p32 or fluorescent labels