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 6

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

Answer 6

Questioned which molecules were responsible for the transformation observed by Griffith

Question 6

Describe the experiment conducted by Avery, MacLeod and McCarthy

Answer 6

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

Question 6

What were the results from Frederick Griffith’s experiment?

Answer 6

-R cells undergone a ‘transformation’ to become S cells
-some form of hereditary material has passed from S bacteria to R bacteria

Question 7

Describe the experiment conducted by Frederick Griffith

Answer 7

-killed S bacteria by heating them to form an extract
-when extract injected into mice, they survived –> extract doesn’t infect mice
-injected mice with extract + live R bacteria
-mice infected + die
live S strain was recovered from dead mice –> R cells became S cells

Question 8

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

Answer 8

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

Question 8

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

Answer 8

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

Question 9

What is a bacteriophage?

Answer 9

-type of virus
-bacterium is host cell

Question 10

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

Answer 10

Which component of a bacteriophage is injected into bacteria?

Question 11

Describe the experiment conducted by Hershey and Chase

Answer 11

-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 12

What are phage ghosts?

Answer 12

The remaining virus on the outside of host

Question 13

What were the results from Hershey + Chases’ experiment?

Answer 13

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

Question 14

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

Answer 14

Radioactive DNA is carried from generation to generation