DNA as the genetic material

Question 1

What are the Mendelian laws of segregation?

Answer 1

-genes come in pairs + one is passed to offspring
-inheritance of a gene doesn’t depend on that of another
-an individual with 2 alleles of a gene will express the dominant

Question 2

What can we assume from Mendel’s laws?

Answer 2

There must be some sort of physical genetic material

Question 3

What is genetic material?

Answer 3

Information that, when passed to a new generation, influences the form + characteristics of each individual

Question 4

What must genetic material be able to do?

Answer 4

-be replicated
-store information
-express the information
-vary by mutation

Question 5

What did Sutton and Boveri’s work show?

Answer 5

-saw that chromosomes were grouped in pairs + separated
-saw gametes had fewer chromosomes
-saw if chromosomes were destroyed, embryos couldn’t develop –> genetic information must be expressed
-saw chromosomes are linear structures with genes along them

Question 6

What did the findings from Sutton and Boveris’ work suggest?

Answer 6

-different combinations of chromosomes could cause variation
-consistent with Mendel’s laws

Question 7

What did Griffith test and what were the results?

Answer 7

-killed S bacteria with heat + injected - mouse wasn’t infected
-killed S bacteria + live R bacteria injected - mouse dies
-killed S bacteria + live R bacteria injected - bacteria have a capsule

Question 8

What did Griffith’s results show?

Answer 8

-the R cells had undergone a ‘transformation’
-some sort of hereditary material has passed from the S to R bacteria, changing the genotype
-the ‘transforming principle’

Question 9

How did Avery, MacLeod and McCarthy go off of Griffith’s work?

Answer 9

Questioned which molecules were responsible for the transformation observed by Griffith

Question 10

Describe the experiment conducted by Avery, MacLeod and McCarthy

Answer 10

-destroyed each component of S strain individually using specific enzymes that digest each molecule
-combined with live R bacteria to test for transformation

Question 11

What were the results from Avery, MacLeod and McCarthy’s experiment?

Answer 11

Polysaccharides, lipids, RNA, protein destroyed - mice contained live S strain
DNA destroyed - mice contained no live S strain + lived

Question 12

What do the results of Avery, MacLeod and McCarthy’s experiment show?

Answer 12

For the bacteria to be virulent, they require DNA encoding for enzymes to make polysaccharide coat, not the polysaccharides themselves

Question 13

What is a bacteriophage?

Answer 13

-type of virus
-bacterium is host cell

Question 14

What was the question Hershey + Chase wanted to answer in 1952?

Answer 14

Which component of a bacteriophage is injected into bacteria?

Question 15

Describe the experiment conducted by Hershey and Chase

Answer 15

-label bacteriophage DNA or protein with radioactive isotope –> in 32P, will have radioactive DNA + in 35S, will have radioactive protein
-infect unlabelled bacteria with radioactive phage
-separate phage ghosts from infected bacteria
-centrifuge to separate phage + bacteria
-test phage + bacteria for radioactivity

Question 16

What are phage ghosts?

Answer 16

The remaining virus on the outside of host

Question 17

What were the results from Hershey + Chases’ experiment?

Answer 17

-found that DNA had been injected into bacteria
-labelled protein recovered in supernatant
-labelled DNA recovered in bacteria

Question 18

What did the results from Hershey + Chases’ experiment suggest?

Answer 18

Radioactive DNA is carried from generation to generation