chapter 2 Flashcards
what type of bacteria did the Griffith experiment use?
-S strain: smooth infectious, has a polysaccharide coating around the cell
-IIS: type 2 coat
-IIIS: type 3 coat
-R strain: rough, harmless, has a mutation that prevents coat.
describe the initial experiment (Griffith)
mice injected with
-S (heat): lived
-IIS living: died
-IIR: lived
conclusion: bacteria had to be alive and have coat to kill mice,
describe the key experiment (griffith) and results
mice injected with:
- IIIS (heat): dead
-IIR living: dead
results: IIIS bacteria was found in the blood of mice.
*IIR transformed into smooth IIS by interaction with dead IIS bacteria.
what is the transform principle?
Griffith concluded that an unknown agent transferred genetic material from the dead IIIS to the material in the living IIR.
describe the controls and variables in the Griffith experiment
-positive control: mice living or dead
-negative control: needle did not kill mice
-independent variables: heat killing bacteria; (manipulated)
-dependent variables: live/dead mice; tested, (measured)
-confounding variable: age of mice, sex, needle (cannot be controlled).
what were the potential transforming principles?
-protein
-DNA
-RNA
-Lipid
-CHO
studied the transformation of R type bacteria to S type; found transforming variable
Avery Experiment
Describe the Avery experiment procedure
broke open S bacteria and injected nuclease and IIR:
-RNASE + IIR= smooth
-Proteinase + IIR= smooth
-Lipase + IIR= smooth
-Carbase + IIR= smooth
-DNASE + IIR= no transformation
results: DNA was the transforming principle, providing IIR with the genetic material.
describe the hersey chase experiment
used bacteriophage to determine whether DNA or protein entered the cell.
-infect e. coli with phages of isotope P or S (DNA contains phosphate and protein contains sulfur). = progeny phages
- e.coli were infected with progeny phages
results: most radioactivity of P was found inside. S was found in phage ghosts (outer layer)
*conclusion: DNA enters the cell and contains genetic info for the next generations.
what are the monomers that make up DNA and RNA?
nucleotides: pentose sugar, nitrogenous base, and a phosphate group
nucleoside
sugar and base
what is the pentose sugar of DNA
deoxyribose: has hydrogen
ribose: has hydroxyl group
pentose sugar of RNA
purines
-adenine and guanine
-nine membered, double ringed
pyrimidines
-thymine, cytosine, uracil
-six membered, single ring
polynucleotides
5-3 prime, phosphate bonds with 3’ carbon of sugar of another molecule
who concluded the 50-50 ratio of purines and pyrimides
Chargaff
Rosalind Franklin
used x-ray diffraction: DNA was a helical structure
Watson and Crick
-double helical structure, antiparallel, sugar-phosphate backbone, H bonds bases.
chromatin
sustainable material in cell nucleus: DNA and proteins
histone proteins
4 types: help organize DNA (wraps twice); have a plus charge
-H2A
-H2B
-H3
-H4
-H1: hydrophobic, brings other nucleosomes together, sticks between other histones.
scaffold proteins
acid base proteins
- pull loops of DNA; stick to scaffold. makes shorter packaging
euchromatin
less packaged. allows DNA to be copied, actively transcribed, genes can be expressed.
heterochromatin
more packaged
what happens during the G1 phase of the cell cycle:
-typical cell function
-1 chromosome
-1 chromatid
S phase
euchromatin opens; DNA is copied
G2 phase
-prepares for mitosis
-2 chromatids: double amount of genes
mitosis
-chromatids pulled apart
-prophase, metaphase, anaphase, telophase
G0 phase
resting
specific set of sequences at the end of a linear sequence and is required for replication
-stabilize the chromosome
-short base sequence (2 per chromosome)
telomeres
what are the two types of repetitive sequence DNA
LINE: long interspersed nuclear elements
- function: help regulate which genes will and will not get utilized, do not code for proteins. 15% genome
SINE: short interspersed nuclear elements
unique sequence DNA
make up genes, single-stranded, proteins 2% genome/DNA
- 20,000 unique genes
