BIOL 222 Lecture Notes - Lecture 10: Heterochromatin, Guanine, Dna Supercoil

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24 Oct 2016

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Biol 222 lecture 10 dna discovery and structure. Genetic material must: store complex information, replicate faithfully, encode for phenotypes. Transforming principle - dna that is transferred from one individual to another in genetic transformation. Griffth"s experiment: s. pneumonia kills mice. S strain wild type, virulent, smooth colony. Makes smooth colonies because of a polysaccarhide that is produced on the surface of the cell. R strain mutant, non-virulent, rough colony: procedure of the griffith experiment. Mixed the dead s strain with live r strain and injected mice. Live s cells are recovered from the dead mouse: conclusion cell debris from the s strain converted the live r strain into live s strain. Identification of the transforming principle avery, macleod, and mccarthy: destroyed either protein, rna, or dna from the s strain. Determined if remaining cellular components would transform the live r strain into an s strain.

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magine that the year is 1928 and the scientific world is in an uproar trying to determine what component of the cell isresponsible for genetic inheritance. Is it DNA, protein, perhaps even RNA? You are busy in your lab, trying to help solve this crucial mystery that still plagues (then) modern day biology. Your work focuses on a microorganism, a bacterium named Streptococcus pneumoniae, and its effects on mice. There are two strains of S. pneumoniae (which is responsible for pneumonia), the âRoughâ strain (R) and âSmoothâ strain (S). The strains are very similar except the S strain has a smooth polysaccharide coat that enables the microorganism to avoid the organismâs immune system and cause illness (and death in mice). The R strain has a rough coat which is detected and dealt with by the immune system (and as a result causes no death in mice). You decide to perform a series of experiments using the R and S strain of S. pneumoniae involving injections of these strains in mice. Your results are documented in the figure below: living S strain of S. pneumoniae mouse dies of infection living R strain of S. pneumoniae mouse lives mouse lives S strain heat-killed living R strain mouse dies of infection living, pathogenic S strain recovered S strain heat-killed From these results, you figure out that something from the heat killed S strain is transforming the R strain into the virulent strain. What is this âTransforming principleâ? Is it related to the cellular component that was passed from one generation to the next? As you know, this was the initial experiment performed by Dr. Frederick Griffith that eventually led to the discovery of the true cellular component that is the genetic inheritance molecule as well as the âtransforming principleâ (Hint: Itâs DNA!).

1. Several experiments were required to demonstrate how traits are inherited. Which scientist or team of scientists first demonstrated that cells contain some component that can be transferred to a new population of cells and permanently cause changes in the new cells?

a. Griffith b. Watson and Crick c. Avery, MacLeod, and McCarty d. Hershey and Chase

2. From your results, which one of the cellular components can be determined NOT to be the component responsible for genetic inheritance? Why?

a. Proteins because these macromolecules become denatured with heat. b. DNA because these macromolecules form a single helix in solution. c. RNA because it's double stranded 100% of the time d. Sugars because glycolysis happens.

3. Which one of the following experimental trials below are considered to be controls for this experiment? a. S Strain grown in 10% ethanol medium. b. Living S strain; Living R strain; Heat Killed S Strain c. Living R Strain with heat killed S strain; Living S Strain d. Heat Killed S strain; Living R strain; R strain grown in 10% ethanol medium

4. Which scientist or team of scientists obtained definitive results demonstrating that DNA is the genetic molecule? a. Griffith b. Watson c. Crick d. Hershey and Chase

5. Hershey and Chase used radiolabeled macromolecules to identify the material that contains heritable information. What radioactive material was used to track DNA during this experiment?

a. 3H b. 14C c. 35S d. 32P

6. DNA molecules, like proteins, consist of a single, long polymeric chain that is assembled from small monomeric subunits.

a. True b. False

7. The polarity of a DNA strand results from the polarity of the nucleotide subunits.

a. True b. False

8. There are five different nucleotides that become incorporates into a DNA strand.

a. True b. False

9. Hydrogen bonds between each nucleotide hold individual DNA strands together.

a. True b. False

brownpanda894

Cystic fibrosis is caused by mutations in the CFTR gene, whichencodes for a chloride channel. You are studying cystic fibrosispatients to determine what mutation they possess in the CFTR gene.The difference between the mutant and wild type CFTR genes can beuncovered by examining the CFTR:

(1 point - partial possible)

DNA

mRNA

protein

You decide to identify the CFTR mutation by analyzing thegenomic DNA of your patients compared to genomic DNA of healthyindividuals. You specifically are looking to see whether a specificgene truncation has occurred in the patients. You will determinethis using hybridization techniques. Which of the following willallow you to accomplish this?

(1 point - partial possible)

Using an RNA probe complementary to the region not removed bythe truncation.

Using an RNA probe complementary to the region removed by thetruncation.

Using an DNA probe complementary to the region not removed bythe truncation.

Using an DNA probe complementary to the region removed by thetruncation.

You would like to ensure that this experiment (to determinewhether patients have a specific CFTR gen truncation usinghybridization) is properly controlled. Which of the followingsamples must you include?

(1 point - partial possible)

The genome of a healthy individual who does not have CFTR.

The genome of a CFTR patient known to have the specifictruncation you are trying to identify.

The genome of a CFTR patient with a point mutation in a separateregion of the gene but without the disease truncation.

The genome of a healthy individual married to a CFTR patientwith the specific truncation you are trying to identify.

The genome of a patient with muscular dystrophy, which can bedue to a trucation in the dystrophin gene.

To conduct the hybridization experiment, you are trying todecide between using a DNA or RNA probe. Which would be a betterchoice and why?

(1 point)

An RNA probe because RNA has uracil bases.

An RNA probe because it could also be used in a translationexperiment.

A DNA probe because it is more stable than RNA.

A DNA probe because RNA cannot bind to DNA.

Which of the following will lower the Tm of a given DNAstrand?

(1 point - partial possible)

Increasing the percentage of GC base pairs.

Raising the pH of the solution from extremely acidic toneutral.

Decreasing the salt concentration in the DNA solution from 50mMNaCl to 5mM NaCl.

None of the above.

Imagine Hershey/Chase had used an RNA virus (genome composed ofRNA) instead of a DNA virus in their experiment. Wouldradioactivity still have been found in the pellet?

(1 point)

A.No, because only DNA can be labeled with radioactivity.

B.No, because the RNA genome would not enter the bacteria uponinfection.

C. No, because while DNA and RNA nucleotides are similar, theyare not identical.

D. Yes, because DNA and RNA nucleotides are similar.

Griffith and Avery's transformation experiments allowed us toidentify that DNA is our genetic information. Which of thefollowing scenarios would result in bacterial cells that arecapable of killing mice upon injection?

(1 point - partial possible)

A. Heat killed non-virulent bacteria is added to a live virulentbacteria strain.

B. Heat killed virulent bacteria is added to a heat killednon-virulent bacteria strain.

C. A heat killed virulent bacteria that is treated with anuclease, is then added to a non-virulent bacteria strain.

D.Heat killed mouse cells are added to a non-virulentbacteria.

The human genome consists mostly of non-coding DNA. Which of thefollowing are benefits of this?

(1 point - partial possible)

A. Random DNA mutations generally won't affect RNA and proteinfunction.

B. It is faster to duplicate the genome when these arepresent.

C. The existence of introns can lead to multiple variations ofproteins encoded by a single gene.

D. Abundant non-coding genome is a protective feature againstthe consequences of transposition of mobile elements.

bronzewater-buffalo862

Question 1

1 pts

Cystic fibrosis is caused by nonsense and missense mutations in the CFTR gene, which encodes for a chloride channel. You are studying cystic fibrosis patients to determine what mutation they possess in the CFTR gene. The difference between the mutant and wild type CFTR genes can be uncovered by examining the CFTR:

	DNA
	mRNA
	protein
	tRNA

Question 2

1 pts

You decide to identify the CFTR mutation by analyzing the genomic DNA of your patients compared to healthy individuals. You specifically are looking to see whether a specific 3' gene truncation has occurred in the patients. You will determine this using hybridization techniques with samples from healthy and CF patients. Which of the following will allow you to accomplish this?

	Using an RNA probe complementary to the region not removed by the truncation.
	Using an RNA probe complementary to the region removed by the truncation.
	Using an DNA probe complementary to the region not removed by the truncation.
	Using an DNA probe complementary to the region removed by the truncation.

Question 3

1 pts

You would like to ensure that this experiment (to determine whether patients have a specific CFTR gene truncation using hybridization) is properly controlled. Which of the following samples must you test?

	The genomic DNA of a healthy individual who does not have cystic fibrosis.
	The genome of a CFTR patient known to have the specific truncation you are trying to identify.
	The genome of a CFTR patient with a missense mutation but full length gene.
	The genome of a healthy individual married to a CFTR patient with the specific truncation you are trying to identify.
	The genome of a patient with muscular dystrophy, which can be due to a trucation in the dystrophin gene.

Question 4

1 pts

To conduct the hybridization experiment, you are trying to decide between using a DNA or RNA probe. Which would be ideal to use and why?

	As both are composed of nucleic acids, using either would result in identical results.
	An RNA probe because RNA has uracil bases.
	An RNA probe because it could also be used in a translation experiment.
	A DNA probe because it is more stable than RNA.
	A DNA probe because RNA cannot bind to DNA.

Question 5

1 pts

Which of the following will lower the Tm of a given DNA strand?

	Increasing the percentage of GC base pairs.
	Raising the pH of the solution from neutral to basic.
	Decreasing the buffer concentration from 50mM NaCl to 5mM NaCl.
	None of the above.

Question 6

1 pts

One step of the Hershey/Chase experiment involved blending the virus/cell mixture before centrifugation and probing the pellet for radioactivity. Why was the blending step necessary?

	To collect the bacteria at the bottom of the tube.
	To break open the bacteria to release the genome.
	To separate the bacteria from the bacteriophages.
	To be able to detect the radioactivity.

Question 7

1 pts

Imagine Hershey/Chase had used an RNA virus (genome composed of RNA) instead of a DNA virus in their experiment. Would radioactivity still have been found in the pellet?

	No, because only DNA can be labeled with radioactivity.
	No, because the RNA genome would not enter the bacteria upon infection.
	No, because while DNA and RNA nucleotides are similar, they are not identical.
	Yes, because DNA and RNA nucleotides are similar.
	Yes, because genome in any form (DNA, RNA, protein) would be labeled similarly.

Question 8

1 pts

Griffith and Avery's transformation experiments allowed us to identify that DNA is our genetic information. Which of the following scenarios would result in bacterial cells that are capable of killing mice upon injection?

	Heat killed non-virulent bacteria is added to a live virulent bacteria strain.
	Heat killed virulent bacteria is added to a heat killed non-virulent bacteria strain.
	A heat killed virulent bacteria that is treated with a nuclease, is then added to a non-virulent bacteria strain.
	Heat killed mouse cells are added to a non-virulent bacteria.

Question 9

1 pts

The human genome consists mostly of non-coding DNA. Which of the following are benefits of this?

	Random DNA mutations generally won't affect RNA and protein function.
	It is faster to duplicate the genome when these are present.
	The existence of introns can lead to multiple variations of proteins encoded by a single gene.
	It is unlikely transposons would exist in the genome if there was too much protein coding DNA.

Question 10

1 pts

Andrew Murray's sister, Andrea, is adding to her brother's work on chromosomes. She is using cells that are unable to synthesize adenine (âade) and histidine (âhis). The plasmid she is currently working with consists of an origin of replication and the Ade gene.

Following her transformation of the plasmid into her yeast, what media will the cells be plated on to select for cells that have picked up the plasmid?

	Media containing histidine
	Media containing adenine
	Media lacking adenine
	Media lacking histidine

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BIOL 222 Lecture Notes - Lecture 10: Heterochromatin, Guanine, Dna Supercoil

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