6.1 Experimental Evidence for DNA as the Genetic Material Flashcards
The genetics functions of DNA flow directly from its?
molecular structure
What is chemically inert
DNA
All the genetic functions of DNA depend on?
Specialised proteins that “read” the information in DNA sequence
F.Meischer (1869) do/ discover?
He extracted “nuclein” from nuclei of human white blood cells. A weakly acidic, phosphorus rich material.
What did chemical analysis of the nuclein reveal
It revealed that nuclein’s major component was deoxyribonucleic acid (DNA)- It contains deoxyribose(sugar)< found in the nucleus and it is acidic
What did staining the cells with Schiff reagent reveal about the location of DNA
Schiff reagent stains DNA red and it revealed that DNA is localized almost exclusively within chromosomes.
What are the three elements of the chemical composition of DNA
- Four kinds of nucleotides linked in a long chain:
1.nitrogenous base: cytosine/guanine/ade-nine/thymine
2. Phosphate
3. deoxyribose sugar
What are phosphodiester bonds
They are covalent bonds joining adjacent nucleotides
What us a polymer
linked chain of subunits
true or false: chromosomes contain more DNA than protein
false, they contain more protein than DNA
Bacterial transformation implicates DNA as the………..
substance of genes
What did F. Griffith (1928) do? also state his dicoveries
He experimented with two strains of Streptococcus pneumoniae(injected into rats). He observed the following:
1. Different in colony morphology and biological activity of the two strains
2. Smooth (S) strain- virulent (wildtype) and causes death
3. Rough (R) strain-nonvirulent (mutation in S form) and doesn’t cause death
4. R cells could be transformed by genetic material transferred from dead (heat-killed)S cells_ making it virulent and deadly (“something” from heat-killed S cells transformed R cells to S cells)
S heat-killed doesn’t cause death
HE IDENTIFIED THAT THERE IS A TRANSFORMING PRINCIPLE
Avery, MacLeod, and McCarthy’s experiment (1944)identified that ………
DNA as the transforming principle
Whose experiment did Avery and associates use to prove this
Griffith’s experiment
Define transformation
The ability of a substance to change the genetic characteristics of an organism.
Why was it believed that protein was the genetic material and not DNA
Because DNA is only made up of 4 different subunits and protein is made up of 20 different subunits, they felt DNA is too simple to specify genetic complexity. Also the fact that chromosomes contain more proteins than DNA
True or false: Everyone was convinced by Avery’s experiment
false
What are bacteriophages?
they are viruses that infect bacteria
Why were phages a good candidate for the Hershey-Chase Waring blender experiment
because they contain roughly equal amounts of protein and DNA
Which bacteriophage was used for The Hershey-Chase Waring blender experiment
T2
