Chapter 11, Nucleic Acid Structure and DNA Flashcards
Genetic material needs to…..(4)
- contain information to build and run an entire organism
- be copied accurately
- be transmitted, passed from parent to offspring (cell to cell)
- Account for the known variation within and between species
_________________ determined what Genetic Material was
a series of experiments
Most scientists believed…
genetic material was proteins since they were known to be much more variable than nucleic acids
There are _____ amino acids and ____ nucleotides
20, 4
________ set stage for showing what genetic material would be in …
Griffith, 1928
Griffith worked with….
two strains of bacteria Streptococcus pneumoniae
The ______ strain was _______ and jilled mice with a pneumonia infection
S (smooth) virulent
The ____ strain was _____ and the mouses immune system would kill it
R (rough) not virulent
Griffith performed ____ experiments
four
Griffith’s first experiment…
- injected mice with S strain and saw that mice died
- after death, living S bacteria were found in the blood
- this established virulence of S strain
control: injected living type S bacteria into mouse
Griffith’s second experiment…
- injected mice with R strain and saw that mice did not die
- dead bacteria were found in the blood
- established non-virulence of R strain
Control: injected living type R bacteria into mouse
Griffith’s third experiment…
- heat killed the virulent S strain and injected the dead S strain
- mice did not die
- bacteria was killed and found inside blood
Control: Injected heat-killed type S bacteria into mouse
Griffith’s fourth experiment…
- he then mixed the live R strain (harmless) with the heat killed S strain (harmless) and injected it into mouse
- Mice did, living S strain was recovered
Control: Injected living R and heat killed S into mouse
Whatever agent that had transformed R into S…
must be the genetic material
This transforming material is called…
transforming factor
__________ did more detailed experiment in _____
Oswald Avery et al., 1944
Published results in
1944
They performed the same part of the fourth experiment which is…
took live R and mixed with heat killed S
Difference in experiment is they…
first treated it with enzymes to destroy some class (or another) of organic molecules
Treated heat killed S strain with _______ to destroy proteins
proteases
When they injected heat killed S with proteases to destroy proteins and then added these to live R proteins …
- the mice still died
- if genes in the heat killed S strain were proteins, they should have been destroyed and not able to transform the live R into the S strain
- therefore GENES (PROTEINS) were NOT genetic material
Treated heat killed S with _____ to destroy nucleic acids
nucleases
When they treated heat-killed S with nucleases to destroy nucleic acids and added this to live R strain
- the mice lived
- genes must consist of nucleic acids since when they are destroyed, so it ability to transform the R strain to the lethal S strain
This was…
first demonstration that genes were nucleic acids