Hersey and chase expriement allowed researches to distinguish between DNA and protein as candidates for phage T2's generica material. Just as a test of your understanding of the experiment, imagine what the results would have been if the genetic material
They would have found 65S label inside the bacteria after treatment with the blender.
-Remember, Herhsey and Chase tagged the phosphorus, which is only in DNA, and sulfur which is only in protein. If the protein had been the genetic material passed on, th
Fraenkel-Conrat and Singer demonstrated ___ to be the genetic material of the tobacco mosaic virus (TMV).
RNA
-Fraenkel-Conrat and Singer separated protein and RNA fractions of two strains of TMV and reconsituted hybrid viruses, with the RNA of one strain and protein of another strain. When they were applied to tobacco plants, each hybrid virus produced the l
Watson and Crick discovered the structure of the DNA molecule to be
a double helix
sugars and phosphate groups alternate to form the backbone of each helix
The nitrogenous bases in DNA and RNA are
single ring pyrimidines and double ring purines
Avery, McCleod and McCarthy showed what to be the transforming principle?
-DNA
Why did Avery, McCleod and McCarthy decide that DNA was the transforming principle?
-The bacteria that had no proteins and no RNA (because of the nucleases) still had bacteria that transformed from good bacteria to virulent bacteria. Bacteria can spontaneously take in DNA and assume that DNA properties.
-however, when a DNAse was added,
Hershey and Chase experiment showed that
DNA is the genetic material of bacteriophage t2
Each nucleotide has polarity. what does this mean?
it has a top and a bottom
All nucleotides in a given strand face the same direction. The nucleotides on the complementary strand all face the same direction too, which is opposite to the direction of the first strand. The two strands are:
complementary and antiparallel
-run in opposite direction, and are backwards copies of the other
What are hairpins in DNA or RNA?
Hydrogen bonding occurs between complementary bases on the same strand.
-unusual secondary structure, and disrupts double helix between two DNA strands
-this structure is associated with disease in DNA
-in RNA hairpins are more common and play an importan
Who proposed cell theory?
Schleiden and Schwann
Griffith
-introduced transformation principle, but did NOT know what caused the transformation
Griffith's transformation principle in detail
-Griffith worked with an R strain (non virulent) and S strain (virulent) of streotpococcus pneumoniae
-s strain had a coating of polysacharrides, allowing it to be less susceptible to antibodies and humans' immune systems
-IIIS in particular was a very de
How did the bacterium like the non virulent type tranform into the virulent, even though it was mixed with DEAD virulent bacteria?
-when the virulent bacteria was heat killed, the DNA was not killed, it was left outside the bacteria, ready to be absorbed
-the non virulent bacteria has the ability to take in a piece of dena from any species and sustitute a portion of it into its own c
Griffith in picture
Did griffith ever find the identity of the transforming principle?
No
avery, macleod and mccarty did it
Avery, MacLeod and McCarty
-transofrming principle is DNA
-in 1944, they took the last set up in griffith's experiment, and added RNA nuclease to 1, DNA nuclease to another one, and protease to a third. The endonucleauses would chop up the dna/rna/protein, rendering it useless and
Why was the s strain virulent versus the r strain?
the s strain had a smooth coating of polysacharrides that allowed it to survive an attack from the nervous system. The R or rough strain did not, and that is way the body is able to fight it off.
Chargaff's rules
G only pairs with C
A only pairs with T or U
he found a 1 to 1 ratio in the pairs
Hershey and Chase: in 1952, experiment with bacteriophage T2, part 1
-bacteriophage is 50% protein (shell) and 50% DNA
-phage sinks into bacteria and releases their genetic material into host. remaining shell is ghost phages.
-takes over bacteria and makes bacteria do what it wants.
Hershey and Chase: in 1952, experiment with bacteriophage T2, part 2
-they labelled DNA with radioactive phosphorus (P-32) which they could track. Phosphorus is only in DNA.
-they labelled S with S-35, also radioactive, and is only in protein.
-they then infeted e.coli with radiolabeled phages
-they then centrifuged and pe
What does H&Chae demonstrate?
1) DNA is what is sent to the cell as genetic inheritance
2) IF they had allowed the infection to proceed, they would have had some DNA labelled in progeny phages!
3) DNA is coding for phenotype of bacteria
4) what went into the cell was the dna
5) but wh
Watson and Crick used Franklin's method to get helical model of DNA
Frankly created xray cyrstallography
her crystal was very clean and pure, and it garnered information about the shape
light goes through atom and bounces back
shadow has a specific shape
Who proved that RNA could also be genetic material?
Fraenkel-Conrat and Singer
on tobacco mosaic virus
What was Fraenkel Conrat and Singer's epxperiment?
-in TMV, they tried to see if RNA or protein produced lesions on plants.
-from two strains of TMV, they diassociated with the virus
-they made hybrid viruses from one strain and protein from the other
-for example RNA from A and protein from B and vice ve
Did the progein in Fraenkel Conrat and singer's experiment have any effect on progeny?
NO
-progeny were the protein AND rna from the virus that donated the RNA.
What is the repeating unit of the DNA polymer
nucleotides
what types of sugars are in nucleotides
pentose sugar ribose and deoxyribose
difference between ribose and deoxyribose
in the 2' carbon, deoxyribose has no oxygen (missing hydroxyl)
-additonal O in ribose makes it more reactive
Where on the sugar is the phosphate attached to? The base?
Phosphate is attached to the 5' sugar
Base is attached to the 1' sugar
what is adenine?
what is guanine
what is cytosine
what is thymine
what is uracil
what is a nucleotide with adenosine called?
-deoxyadenosine g'-monophosphate (dAMP)
What is a nucleotide with guanine called?
-deoxyguanosine 5'-monophosphate (dGMP)
What is a nucleotide with thymine called?
-Deoxythymadine 5'-monophosphate (dTMP)
What is a nucleotide with cytosine called?
-deoxycytodine 5'-monophosphate (dCMP)
What are the pyramidines?
what are purines? What are the difference in purines?
How to tell the nucleotides apart
Guanine - double ring, has one carbonyl and one amine
Adenine - double ring, has no carbonyls, and one amine
Cysotine - single ring, has one carbonyl and one amine
Thymine - single ring, has two carbonyls, and one methyl
uracil - single ring, has two caro
Why can thymine and uracil substitute for each other?
They've got the same structure except thymine has a methyl, on the 5 carbon and uracil has CH on the 5 carbon, making the uracil more reactive and the DNA more repressed from expression.
The two strands in the double helix are both
complementary and antiparallel
-one strang is complementary and 5'-3' which hudrogen bonds with another strand that is 3'-5'
Each sugar molecule has polarity. What is the top and what is the bottom?
-top of the sugar molecule is 5' end
-bottom is 3' end
-each nucleotide therefore has polarity and gives the wohle DNA strand polarity
What bonds are nucleotides linked with
phosphodiester bonds
-bond of strong covalent bonds between phosphate group and two 5 carbon pentoses over two ester bonds.
How are links of a strand made?
-molecule is polar.
-backbone of dna is composed of alternating sugar and phosphate molecules.
-5' is connected to oxygen in phosphate which is then connected to 3' of another pentose sugar
5' to phosphate to 3'
When stacked, how do the bases create a helix?
Each base is 36 degrees shifted than the other ten base pairs. All ten are needed to get around.
Where do proteins attach to DNA?
-the minor groove
-the major groove
What type of double helix does DNa form?
-right handed helix
-clockwise direction results in a motion away from you
What are the levels of DNA structure?
primary - order and sequence of nucleotides which has the information content
secondary - double helix - antiparralel and complementary
-tertiary - higher level folding beyond double helix, such as z, B, A dna
What are the three tertiary structures od DNA
A DNA is:
-when solution is 75% water
-the helix direction is right handed
-the overall shape is short and wide
B DNA is:
-when solution is 92% water
-helix is still right handed
-this is perfect for DNA, angle of rotation is 36 degrees
-long and narrow
Z
Information transfer
-DNA to DNA is DNA replication
-DNA to RNA is Transcription
-RNA to DNA is Translation
What is the central dogma of molecular biology?
DNA to RNA to Protein
-however sometimes there are exceptions such as reverse transcription (retroviruses) and RNA to RNA replication
What is a reverse transcription
virus has rna
then forces DNA to transcribe RNA and protein per its genetic information
What are inverted repeats?
-sequences that read the same 5' to 3' on opposite strands
-one section is complementary to the other section on the same strand
-there are non complementary bases between inverted repeas
-5'-aaag...cttt- 3'
-3' - tttc...gaaa- 5'
Some inverted repeats are palindromes
palindromes are where inverted repeats are complementary to iself
What are some special secondary structures
Hair pin
when there are complementary pairs on the same strand, and they form a loop
What is a cruciform
A hair pin on two ends
which has more possibilities of secondary structure, DNA or RNA?
RNA obciously because it's single stranded
-DNA structure is sequence independent because it is dependent on a complementary strand
-RNA on the other hand IS sequenc dependent and it is only select parts of a molcecule, so lots of diversity
What are some ways of modifying DNA structure?
-methylation
-DNA bending
-protien bending
How does methylation modify DNA?
-methylation adds a methyl group to cytosine
-this helps to silence genes
Methylation of histones
-associated with higher levels of gene expression
-methyl group (or other binding factor, such as an acetyl (CHO) group) interacts with histone tails, making them unavailable for folding the DNA
-histones that are methylated or acetylated don't form as ti
How does DNA bending modify DNA
-helps to control gene expression
Melting DNA
-is to break the hydrogen bonds between the strands
-is done during DNA replication in interphase
DNA replication happens in
interphase
Making of RNA from DNA is
transcription
making of protein from RNA is
translation
Exceptions to the central dogma are: 2 items
-reverse transcription in retroviruses in which RNA makes DNA
-RNA replication in which DNA is replicated to make more RNA
In E.coli, what catalyzes the phosphodiester bonds in DNA?
DNA polymerase III
What enzyme breaks the hydrogen bonds in a double helix?
helicase
Each chromatid
represents on continuous molecule of DNA, is 700 nm wide, and consists of multiple loops of 250-300nm fibers, attached to a non histone scaffold
histones are alkaline which means
-they are positively charged
-like lysine and arginine
On a karyotype, what would heterochromatin look like?
Darker bands
euchromatin would be lighter bands