Maria Chiaffarano<br />Bartel and Szostak Experiment<br />
HOW DID LIFE BEGIN?<br />
Four Overlapping Stages<br />Scientists used four stages to understand the origin of life <br />Stage 1 <br />Nucleotides ...
Chemical Selection<br />What is chemical selection? <br />Chemical within a mixture has special advantageous properties <b...
RNA World<br />Scientists believe that the world used to consist of RNA based organisms <br />Studied the building blocks ...
Key Functions of RNA<br />RNA has three key functions that encourage scientists to favor it as the first macromolecule fou...
ADDITIONAL ADVANTAGES OF RNA<br />DNA and proteins are not as versatile as RNA <br />DNA has limited catalytic activity <b...
Bartel and Szostak Experiment<br />David Bartel and Jack Szostak<br />First study that used RNA molecules with a particula...
Materials<br />Many copies of short RNA <br />Had a tag sequence that binds tightly to “beads” (column packing material) <...
Overview of the experiment<br />
Step 1<br />The long RNAs and short RNAs were incubated together <br />Promote hydrogen bonding<br />Time was given for th...
Step 2<br />The mixture passed through a column of beads <br />The beads would bind to the tag sequence of the short RNA o...
Step 3 	<br />The main purpose of this step was to get rid of the beads<br />Low pH solution was added in order to prevent...
Step 4<br />Pool #1 was used to make a second batch of long RNA molecules <br />Polymerase chain reaction (PCR) was used<b...
Steps 5 & 6<br />The procedure was repeated in order to generate 10 consecutive pools of RNA molecules <br />A sample of t...
Conclusion<br />Data:<br />Chemical selection is possible<br />Scientists knew this because the experiment showed that the...
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Biology bartel and szostak experiment

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Biology bartel and szostak experiment

  1. 1. Maria Chiaffarano<br />Bartel and Szostak Experiment<br />
  2. 2. HOW DID LIFE BEGIN?<br />
  3. 3. Four Overlapping Stages<br />Scientists used four stages to understand the origin of life <br />Stage 1 <br />Nucleotides and amino acids were produced prior to the existence of cells<br />Stage 2<br />Nucleotides became polymerized to form RNA and/or DNA and amino acids become polymerized to form proteins<br />Stage 3<br />Polymers became enclosed in membranes<br />Stage 4 <br />Polymers enclosed in membranes acquired cellular properties<br />
  4. 4. Chemical Selection<br />What is chemical selection? <br />Chemical within a mixture has special advantageous properties <br />Properties allow it to increase in amount <br />Hypothesis <br />The cellular characteristics that exist today evolved from an “RNA world” <br />
  5. 5. RNA World<br />Scientists believe that the world used to consist of RNA based organisms <br />Studied the building blocks <br />Amino acids and nucleotides <br />
  6. 6. Key Functions of RNA<br />RNA has three key functions that encourage scientists to favor it as the first macromolecule found in protobionts<br />Ability to store information in its nucleotides<br />Nucleotide sequence has the capacity for self-replication <br />RNA has many enzymatic functions <br />Act as ribozymes <br />
  7. 7. ADDITIONAL ADVANTAGES OF RNA<br />DNA and proteins are not as versatile as RNA <br />DNA has limited catalytic activity <br />Proteins do not undergo self-replication <br />However:<br />RNA can perform functions that are characteristics of proteins while simultaneously serving as genetic material with replicative and informational functions <br />
  8. 8. Bartel and Szostak Experiment<br />David Bartel and Jack Szostak<br />First study that used RNA molecules with a particular function (1993)<br />Synthesized a mixture of 10^15 RNA molecules also known as “long RNA” <br />First region (5’ end) constant region among all “long RNAs” (identical) <br />Second region, variable region (220 nucleotides) <br />Hypothesized that the variable region could possibly result in long RNA with the enzymatic ability to catalyze a covalent bond between two adjacent nucleotides <br />
  9. 9. Materials<br />Many copies of short RNA <br />Had a tag sequence that binds tightly to “beads” (column packing material) <br />Had a complementary sequence to a site in the constant region of the long RNA <br />No variable region, all the same<br />Long RNAs with the constant and variable regions <br />Variable regions were made using a PCR step (caused mutations in the region) <br />
  10. 10. Overview of the experiment<br />
  11. 11. Step 1<br />The long RNAs and short RNAs were incubated together <br />Promote hydrogen bonding<br />Time was given for the molecules to form covalent connections (only if the RNA had the enzymatic ability to form covalent bonds) <br />The long RNA molecule variable regions may rarely have enzymatic ability to connect the 3’end of short RNA to 5’end of long RNA <br />
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  13. 13. Step 2<br />The mixture passed through a column of beads <br />The beads would bind to the tag sequence of the short RNA only! <br />Tag sequence promoted the binding of the short RNA to the beads<br />IF the long RNA had the ability to bind to the short RNA, it would also be attached to the beads <br />Additional liquid was added to filter out the long RNAs that did not covalently bond to the short RNAs <br />
  14. 14. Step 3 <br />The main purpose of this step was to get rid of the beads<br />Low pH solution was added in order to prevent the tag sequence from binding to the beads <br />The tightly bound RNAs are flushed out of the column <br />They were flushed into a flask and labeled “Pool #1” <br />Beads were left behind <br />
  15. 15. Step 4<br />Pool #1 was used to make a second batch of long RNA molecules <br />Polymerase chain reaction (PCR) was used<br />Variable regions were derived from the variable regions of pool #1 RNA molecules, expected to have enzymatic activity <br />Reverse transcriptase was used to make cDNA<br />PCR primers recognized beginning and end of the long RNA sequence and copied only this region <br />cDNA used as a template to make long RNA via RNA polymerase<br />
  16. 16. Steps 5 & 6<br />The procedure was repeated in order to generate 10 consecutive pools of RNA molecules <br />A sample of the original population (Pool #1) and each of the following 10 pools were collected in order to test for the enzymatic ability to catalyze a covalent bond between adjacent nucleotides <br />
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  18. 18. Conclusion<br />Data:<br />Chemical selection is possible<br />Scientists knew this because the experiment showed that there was an increase in covalent bond formation from pool 1 to pool 10 <br />In each generation, the catalytic enzyme activity increased <br />Pool #10’s enzymatic activity was approximately 3 million times higher than the original random pool of molecules<br />

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