Ch. 10 DNA Structure & Analysis (Exam 1) Flashcards
What is the central dogma of molecular genetics?
DNA transcribes to RNA which translates into proteins
What are the 4 special roles of genetic material?
1) Replication
2) Storage of genetic info
3) Gene expression
4) Variation
In Griffith’s transformation experiment, which control sample killed the mouse?
IIIS (smooth virulent)
In Griffith’s transformation experiment, why did the mouse in the 2nd control group survive after getting injected?
It was given one shot of IIR (rough avirulent) at first and then later another shot w/ heat-killed IIIS
In Griffith’s experiment, what was in the experimental group injection that killed the mouse?
The mouse was injected with IIR and heat-killed IIIS at the same time
What was Griffith’s experimental conclusion?
A chemical component of a cell could introduce a new, heritable trait to another cell
What did Avery et al. want to know from Griffith’s experiment?
They wanted to know how avirulent IIR became virulent IIIS
How was the Avery et al. experiment prepared?
IIIS was centrifuged, heat-killed, homogenized, and filtrated. One control group and three experimental groups were tested. The experimental groups treated the IIIS filtrate with protease, RNase, and DNase, respectively
What was the conclusion of Avery et al.’s experiment?
DNase-treated IIIS filtrate effectively neutralized the development of the harmful IIIS cells (leaving only IIR cells) and revealed that DNA is the active factor that carries heredity
Hershey-Chase showed that proteins and DNA contained which elements?
Sulfur and phosphorus, respectively
Which radioisotopes did Hershey-Chase use to show identify proteins and DNA?
Sulfur-35 and Phosphorus-32, respectively
How did Hershey-Chase conduct the experiment?
They took 2 phage T2s and injected one w/ phosphorus-32 and another w/ sulfur-35 to keep track of their genetic information. The phages then infected separate bacterial cells to see what radioactive material would pass to the bacterial cell
What did Hershey-Chase conclude, and what did this say about the locations of proteins and DNA?
The phosphorus phage’s radioactive material infected the bacterial cell with DNA, but the sulfur phage remained radioactive, and no protein was passed. Protein is found throughout the cell, but DNA is only in the nucleus
What was Chargaff’s 1947 consensus about DNA composition amongst all species of life?
DNA composition varies from species to species
What 3 features make up a nucleotide?
1) Nitrogenous base
2) Pentose
3) Phosphate group
What are 2 types of nitrogenous base rings?
1) Pyrimidine rings
2) Purine rings
Which 3 nitrogenous bases are considered pyrimidine rings?
1) Cytosine
2) Uracil
3) Thymine
Which 2 nitrogenous bases are considered purine rings?
1) Guanine
2) Adenine
What 2 types of pentose make up RNA and DNA?
Ribose and 2-deoxyribose, respectively
What is the difference between ribose and 2-deoxyribose?
Ribose has an OH group at C’2 while 2-deoxyribose has a proton at C’2
What is the difference between a nucleoside and a nucleotide?
Nucleotides has 3 structures: n-base, pentose, AND a phosphate group. Nucleosides only have the n-base and pentose (NOTE: nucleoTide - Three)
What bond links 2 nucleotides together?
3’ to 5’ phosphodiester bond
At which carbons do we find 3’ to 5’ phosphodiester bonds?
C3 of one ribose links to C5 of another
What technique did Rosalind Franklin use to study DNA?
X-ray crystallography
What 3 conclusions did Rosalind Franklin reach?
1) DNA is helical
2) There is a repeating unit of 3.4 Angstrom
3) There is another repeating unit of 34 Angstrom
Do Chargaff’s rules apply to single-stranded or double-stranded DNA?
Double-stranded DNA
What are Chargaff’s rules?
1) A:T in 1:1 ratio
2) C:G in 1:1 ratio
3) (C+G)% is not equal to (A+T)%
How many Angstrom are in a complete turn of DNA?
34 Angstrom
What are the 4 key characteristics of a DNA molecule?
1) Double-stranded helix
2) Complimentary (A:T, C:G)
3) Anti-parallel strands
4) Alternating sugar-phosphate backbone
What are the 2 types of centrifugation?
1) Sedimentation EQUILIBRIUM centrifugation
2) Sedimentation VELOCITY centrifugaion
What is density-gradient centrifugation also called?
Sedimentation equilibrium centrifugation
What type of gradient is DNA spun w/ in DG centrifugation? Example?
A heavy metal salt such as cesium chloride (CsCl)
What is the goal of DG centrifugation?
DNA is spun around until it reaches its buoyant density
What is the relationship between G+C content and buoyant density?
G+C content and density are directly proportional (^G+C=^density)
What does velocity sedimentation measure?
Velocity sedimentation measures how fast DNA reaches its buoyant density
What coefficient (S) calculates the velocity of sedimentation?
Svedberg coefficient
What physical property of DNA does the Svedberg coefficient (S) determine?
Molecular weight
How is the melting point of DNA determined?
The temperature at which 1/2 of the DNA molecules in a sample become single-stranded is the melting point
What is the relationship between G+C content, H-bonds, and the heat of a DNA melting point?
G+C content, the # of H-bonds, and heat needed to break these H-bonds are directly proportional (^G+C content = ^H-bonds = ^heat needed to break H-bonds)
What is the graph that is used to show differences in DNA melting points?
Hyperchromic shift
What can differing DNA melting points tell us from looking at a hyperchromic shift?
Differing DNA melting points can tell us about relative G+C contents
How can we renature DNA?
DNA can be renatured by cooling it down
What technique is used to separate DNA fragments based on size/length?
Electrophoresis
How does DNA travel down agarose gel during electrophoresis?
Negatively-charged DNA goes to the positively-charged anode
What is the relationship between fragment size and migratory speed down the agarose gel?
Shorter fragments at bottom b/c shorter = faster
