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UMDEARBORN / Biology / BIOL 306 / Does the dna or protein part of the phage serve as the genetic materia

Does the dna or protein part of the phage serve as the genetic materia

Does the dna or protein part of the phage serve as the genetic materia


School: University of Michigan - Dearborn
Department: Biology
Course: Genetics
Professor: John thomas
Term: Fall 2018
Tags: Genetics
Cost: 25
Name: BIOL 306, week 2 notes
Description: These notes cover the material covered in lecture as well as the notes included in the powerpoint. There are also available book notes for Chapter 10.
Uploaded: 09/20/2018
11 Pages 132 Views 2 Unlocks

BIOL 306-Gentics Notes 

Does the dna or protein part of the phage serve as the genetic material and is transmitted to the phage progeny?

[A continuation of last week’s notes and this week’s notes. Includes chapter  10 and some of chapter 11 from the book and PowerPoints.]

Chapter 10 ppt notes 09/14/18 

*important to note: the Hopi culture traditionally treated albinos with  respect, they were looked at as being special and were awarded. The Hopi  tribe traditionally did farm work, therefore, albino males did not have to work and spent most of their times in the village so they would not be harmed by  the sun. By spending most of their time in the village, this gave them a  mating advantage allowing them to reproduce more. Due to the way that the Hopi tribe viewed albinism, as a purity in the village, they allowed the  increase in the allele frequency of the gene.

What substances, rna or protein, carries the genetic material in tobacco mosaic virus (tmv)?

 Hershey and Chase Experiment (slide image 11 and 12) We also discuss several other topics like What does convergence mean?

Question: does the DNA or Protein part of the Phage serve as the  genetic material and is transmitted to the phage progeny?

Part 1:

1. Using T2 Phage, which contains both DNA and Protein, infect E.Coli  that has been grown in the medium containing 35S. If you want to learn more check out What is an atomic orbital?

2. 35S is then taken up in the Phage protein section, which contains S  but not P.

3. Phages with 35S then went on to infect unlabeled E.Coli 4. The mixture is then placed in a blender where the protein coats are  sheared off.

5. The protein is then separated from the cells by centrifuging. 6. After being centrifuged, 35S is able to be recovered from the fluid  containing the virus coats.

Is rna or protein for genetic material?

7. There was no radioactivity detected, this means that protein has not been transmitted to the progeny phages.

Part 2:

1. Using E. coli, they infect E.coli grown in medium containing 32P. 2. 32P is then taken up in the phage DNA, which contains P but not S  in this circumstance.

3. Phages that have 32P will infect unlabeled E.coli.

4. Protein coats are then sheared off in the blender.

5. The proteins are then separated from the cells by centrifuging. 6. After being centrifuged, the infected bacteria form a pellet that  contains 32P at the bottom of the tube.

7. There is radioactivity in the progeny phages, this means that DNA  has been transmitted to the progeny phages.Don't forget about the age old question of Who did beowulf rescue?

Conclusion: DNA is the genetic material in bacteriophages, not protein.  Three Competing Models of Replication (slide image 13) Don't forget about the age old question of How does marketing create value?

DNA is composed of a double helix/strands, a feature of having two  strands is that DNA should be able to replicate or encode another strand.

1. Semiconservative Replication: produces two copies that each contain  one of the original strands and one new strand.

2. Conservative Replication: this produces two original template DNA  strands together in a double helix and would also produce a copy that  is composed of two new strands that contain all of the new DNA base  pairs.

3. Dispersive Replication: this form of replications uses the original DNA  chain and breaks it into pieces that are then recombined in a random  fashion with the new strands.

The Meselson-Stahl Experiment 

∙ In 1958: Meselson and Stahl used cesium chloride (CsCl) centrifugation to test the “Three Competing Models of Replication” for DNA. ∙ Centrifugation: the process by which a mixture is separated through  spinning REALLY FAST. This process is able to separate molecule with  slightly different molecular weights. Don't forget about the age old question of Why is directly observing electrons impossible?
Don't forget about the age old question of What are the three categories of managerial roles according to mintzberg?

∙ Meselson and Stahl began their experiment by growing E.coli in a  medium containing heavy nitrogen, also known as N15, for many  generations.

∙ Once all of the bacterial cells in the culture had DNA that only  contained heavy nitrogen, they transferred the bacteria to medium  containing N14.

∙ After a single round of replication, the DNA of an aliquot of cells was  isolated and centrifuged in order to determine its density.

∙ The same step was repeated after the successive replication cycles. ∙ IMAGE ON SLIDE 20 explains more and describes the results. ∙ Conservative replication is wrong because the results of the first cycle  

contain two bands while the actual results from the Meselson-Stahl  experiment prove that there should only be one band.

∙ Dispersive Replication is able to be eliminated because the random  mixture of DNA sequences. If this was so, the Meselson-Stahl  experiment would have shown a smear in the second cycle rather than clear bands.

∙ Semiconservative replication is the most probable method of DNA  replication since the first and second cycle outcomes correlate with  Meselson-Stahl experiment results.

 Rolling Circle Replication slide image 22 : A process in which there is  unidirectional nucleic acid replication, this can very quickly synthesize  multiple copies of circular molecules of DNA or RNA. For example: plasmids,  the genomes of bacteriophages, and the circular RNA genome of viroids.

*ALL genetic information is encoded in the structures of DNA or RNA

Image 10.7 Slide 24 : This is an X-ray diffraction image of DNA. 1. X-rays are aimed at crystals of a substance which are then diffracted. 2. The spacing of the atoms within the crystal enables us to determine  

the diffraction pattern, this appears as spots on a photographic film. 3. The diffraction pattern provides information about the structure of the  molecule.

*Watson and Crick used Rosalind Franklin’s X-ray image of DNA, as well as  other means, to determine the three-dimensional structure of DNA.

*In most organism’s DNA carries the genetic information, while in some  organism’s RNA carries the genetic information.

 Tobacco Mosaic Virus image 10.9 slide 27 

Question: What substances, RNA or Protein, carries the genetic  material in tobacco mosaic virus (TMV)?


1. Type A TMV and Type B TMV are both degraded.

2. This allows them to yield RNA and coat proteins.

3. Then RNA of one type is mixed with the protein of the other type,  for both.

4. This creates hybrid viruses.

5. Use the hybrid viruses to infect tobacco.  

6. The type of RNA in the hybrid parent TMV determines the RNA and  protein of progeny viruses.

Conclusion: RNA is the genetic material of TMV.

The Primary Structure of DNA 

DNA consists of two complementary and antiparallel nucleotide strands that  form a double helix. DNA- Deoxyribonucleic acid- has three parts: a  phosphate, sugar, and a base. There are purine and pyrimidine bases.

Purine: adenine and guanine.

Pyrimidine: cytosine, thymine (present in DNA), and uracil (present in RNA). Phosphates are negatively charged, while histones are positively charged.  

 Table 10.2 Names of DNA bases, nucleotides, and nucleosides (image slide  33) 

The Secondary Structure of DNA 

Double Helix of DNA: two strands that wrap around each other, can be  compared to a twisted ladder.

The backbone of DNA is formed through phosphodiester bonds.

Complementary bas pairing: Adenine pairs with thymine, while guanine pairs with cytosine.

The nucleotides in a base pair are complementary, therefore their shapes  allow them to bond to each other with hydrogen bonds. Adenine and thymine pair forms two hydrogen bonds, while cytosine and guanine pair forms three  hydrogen bonds.

Hydrogen bonding: the hydrogen bonding between complementary base  pairs is what holds the two strands of DNA together.

The strands of DNA run in opposite directions meaning they are antiparallel.

The antiparallel nature of DNA refers to: the opposite direction of the two  strands of nucleotides.

DNA Backbone: consists of deoxyribose sugar linked by phosphate Differences between RNA and DNA 

*There are many differences but here are a few:

DNA consists of Deoxyribose sugar (no oxygen), while RNA consists of  Ribose sugar (has oxygen, OH group).  

In RNA uracil replaces thymine as the complementary base for  adenine.

 3-D structure identified by Watson and Crick image 10.15

B-DNA: is the most common double helical structure found in nature. The  double helix is known to be right-handed and has about 10-10.5 base pairs  per turn.

*important to note Professor skipped slides 41-49, still open to be reviewed  online.

Chapter 10 Book notes 

Summary Table:

Influential Person


Fredrick Griffith

Carried out the experiment with the  mouse testing with the smooth and  rough strain of pneumococcus.  (testing for pneumonia)

Erwin Chargaff

Chargaff’s rule: DNA from any cell  should have a 1:1 ratio of pyrimidine and purine bases. A=T, G=C

Avery, Macleod, and McCarthy

Went off of Griffiths findings and  conducted a mouse experiment of  their own. Tested whether genetic  material was contained in RNA, DNA, or Proteins. Concluded that genetic  material is in DNA. (used enzymes)

Rosalind Franklin

A geo-biophysicist, one of the first to study DNA in a more detailed  manner. First to take an X-ray image  of DNA.

Watson and Crick

Used Rosalind Franklin’s X-ray image of DNA to determine that the 3D  structure of DNA. Discovered that  DNA has a double helix.

Hershey and Chase

Conducted an experiment to  

determine whether DNA or Protein  carries the genetic material. Used  35S and 32P, found 32P present  concluding that DNA is the genetic  material.

Fraenkal-Conrat and Singer

Conducted the Tobacco Mosaic Virus  Experiment. Is RNA or Protein for  genetic material? Switched the coats and the new generation went back  to normal concluded that RNA is for

the genetic material.

Meselson and Stahl

They were testing the three  

competing models of DNA  

replication. Grew E.coli in N15 and  N14. The first and second cycle  canceled out conservative  

replication and dispersive  

replication. The results of the  experiment correlated most with  semi-conservative replication and  that has been determined to be the  way that DNA replicates.

 ∙      10.1 Genetic Material Possesses Several Key Characteristics o Genetic material must contain complex information

 Because it is capable of storing large amounts of  


o Genetic material must replicate faithfully

 To make an animal, a cell must undergo billions of cell  

divisions, and the genetic instructions must be accurately  

transmitted to descendant cells

 Genetic instructions must be copied with fidelity

o Genetic material must encode the phenotype

 Genetic material (genotype) must have the capacity to be  expressed as a phenotype to code for traits

 The product is often a protein or RNA molecule

o Genetic material must have the capacity to vary

 Genetic info must have the ability to vary because different species, and even individual members of the same species, differ in the genetic makeup.

 ∙      10.2 All Genetic Information is Encoded in the  

Structure of DNA or RNA 

o Johann Miescher established that the nuclear material contained  a novel substance that was slightly acidic and high in phosphorus

 Now know it was protein and DNA

 He called it nuclein and later named nucleic acid by his  students

o By 1887, researchers concluded that the basis of heredity lies in  the nucleus

o Chromatin was shown to consist of nucleic acid and proteins but  which was actually the genetic info, that wa not clear

o Kossel carried out an experiment and determined DNA contains  four nitrogenous bases: adenine, cytosine, guanine, and thymine

o Phoebus Levene discovered that DNA consists of a large number  of linked, repeating units, called nucleotides (consisting of a  sugar, phosphate and a base)

 But he thought that the bases were in a fixed order  therefore not variable enough to make it the genetic  material

o Erwin Chargaff found that the amount of A=T and C=G  Also that A/T and C/G=1

o A huge step to labeling DNA as the genetic info was the  discovery of transformation

 Observed with Fred Griffith who studied the smooth and  rough pneumoniae

o Avery, Colin MacLeod, and Maclyn McCarty isolated the  transforming substance and matched it to DNA or Protein by  using DNase, Protease, and RNase.

o Hershey-Chase then used phosphate and sulfur isotopes and  figured out that the genetic material is DNA

o Watson and Crick used all these previous experiments and  Franklin’s x-ray diffraction to back up that DNA was the genetic  material

o BUT RNA also is genetic material for viruses.  

 Fraenkel-Conrat and Singer worked with tobacco mosaic  virus (infected tobacco plants)

 Found that the genetic material was in the RNA not  the Protein

 ∙      10.3 DNA Consists of Two Complementary and  

Antiparallel Nucleotide Strands That Form a Double  Helix 

o DNA is a polymer, that is a chain made up of many repeating  units linked together (repeated units of DNA= nucleotides)

o Sugar of nucleic acids=pentose sugars (five carbon atoms)

o The sugars of DNA is deoxyribose (does not have an OH on the 2  prime) and that of RNA is ribose (has an OH on the 2 prime)

o A sugar (ribose or deoxyribose) + a base (A,C,T,G,U) =  nucleoside

 Adenine and Guanine are purines (Pure As Gold) (two rings)  Cytosine, Thymine, and Uracil are all pyrimidines (one ring)

o The nucleotides are connected by covalent bonds and these  bonds are called phosphodiester linkages (strong covalent  bonds)

 A series of nucleotides linked this way gives a  

polynucleotide strand

 The backbone is a sugar phosphate backbone

o DNA is a double helix, the strands are lined up in opposite  direction therefore antiparallel, the two strands are also not  identical but complementary DNA strands

∙ 10.4 Special Structures Can Form in DNA and RNA 

o Single strands of nucleotides form a hairpin, they can form a  stem shape or a secondary complex structure.

o Three stranded (triples) structures are called H-DNA, some of the DNA unwinds and a single polynucleotide strand from one part of the molecule pairs with double-stranded DNA from another part  of the molecule

o DNA can be modified:

 DNA methylation, the process of adding CH3 to certain  positions on the nitrogenous bases

 Bacterial DNA is often methylated to distinguish from

unmethylated viruses.

 Example is 5-methylcytosine

Chapter 11 ppt Notes 9/18/18 


Some DNA is circular, linear, or has a somewhat U shape in it. DNA is located in the nucleus of the cell.

DNA is coiled together to form rope-like chromosomes.

In order to make RNA or carry out DNA replication the chromosomes  must untie.

*When a person becomes sunburnt a: Mutation, repair, and restructure has  occurred.  

DNA must be tightly packed to fit into a cell.

 Supercoiling: DNA supercoiling is when there is over- and or under- winding  of a DNA strand.

1. Positive supercoiling: this occurs when the right-handed, double helical conformation of DNA is twisted very tightly until the helix starts to  knot.

2. Negative supercoiling: this is the uncoiling of DNA strands performed in a left-handed direction.

3. Topoisomerase: this is the enzyme that adds coils in positive  supercoiling while removing turns in negative supercoiling.

*Important note: early childhood stress is linked to shorter telomeres.

 Telomeres, Aging, and Cancer: Telomeres have been known to be linked with  aging and cancer.

Telomere: a telomere is the structure at the end of a chromosome. Telomeres shorten with age, the rate of telomere shortening may indicate the pace of  age.

Telomere length is not only important when dealing with age, but is also  important for chromosome stability, cell longevity, and reproductive success.

Telomerase: an enzyme that functions by adding nucleotides to telomeres.  This is increased in cancer cells.

Telomerase inactivity tends to be associated with the normal aging of cells.

Telomerase is also active in germ-line cells and a few stem cells in  eukaryotes.

A cell with no telomerase activity, consequently, has a limited life span (on  average 30-50 cell divisions). Differentiated somatic cells and cells in culture  are such cells.

Werner Syndrome: (aka adult progeria) is a rare, autosomal recessive  disorder that is hereditary. Is characterized by premature aging and an  increased risk of cancer as well as other diseases. Named after the German  scientist Otto Werner, the first to describe it in his doctoral thesis.

Someone who has Werner Syndrome does not go through the usual  growth spurt during their teenage years, they tend to be shorter than  others.

Cause: a mutation in RECQL2 – a gene that encodes a helicase that is  required for telomerase activity.

Damage to Mitochondrial DNA: also associated with aging

­ Tend to appear in middle age or later

­ Those with the mutations start life with decreased oxidative  phosphorylation capacity.

­ Oxidative Phosphorylation Capacity: Is at its maximum when born,  declines with age.

­ Mechanism of damage is unknown

­ As of now *September 2018: stress has been known to be correlated with increases mtDNA in circulating blood.

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