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36 Cards in this Set
- Front
- Back
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What did the Bernard Davis' U-tube experiment prove?
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Need contact between bacteria for Lederberg's results.
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How is DNA transferred from host to donor cell?
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Transferred as single stranded DNA from donor cell to recipient cell. Recircularized, and used as template for replication. Made double stranded in recipient.
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What is a transconjugate?
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Receives DNA as a result of conjugation. Recipient.
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What is a self-transmissable plasmid?
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Contains all functions necessary for conjugation. (tra+, mob+)
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What is a mobilizable plasmid?
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contains some, but not all functions necessary for conjugation. (mob+)
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What gene is responsible for pillus biogenesis?
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trans acting (tra-).
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4 characteristics of pillus?
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~10 nm in width, can be microns long
contains central channel retracts after binding DNA does NOT go through pillus |
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Why does the pillus retract after binding?
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To bring the 2 cells closer.
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What is the oriT?
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Origin of transfer. Cis-acting site on the plasmid.
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What do mob genes do?
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Prepare plasmid for DNA transfer.
Encode proteins that make up relaxosome. |
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What is the function of relaxase?
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Makes single strand cut in plasmid at nic site within oriT.
Recircularizes plasmid after transfer into recipient. breaks phospodiester bond and transfers bond to tyrosine on itself. end up with relaxase covalentely bound to ssDNA. bound at 5' end. |
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What do mob genes encode?
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proteins that make up relaxosome.
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How do you make ssDNA into dsDNA?
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RNA primer! Primase comes from donor cell.
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Why wouldn't cell use host machinery (RNA Primase)?
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Could be distantly related microorganism.
Sending over specific donor primase ensures copying to dsDNA. |
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Is conjugation in gram positive or gram negative?
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Gram positive, because there is no 2nd membrane.
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What is the difference between biparental and triparental mating?
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In biparental mating, one cell has all genes needed and transfers them to recipient.
In triparental, a "helper" cell is needed. Donor cell is missing one (or more?) required gene. Gets it from helper cell, then transfers to recipient. |
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4 things about hfr (high frequency recombination) strains in E. coli.
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transfer chromosomal DNA from donor to recipient
self-transmissable plasmid had incorporated onto the chromosome takes ~100 min to transfer entire E. coli chromosome F plasmid |
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What is a transposon?
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DNA element that can hop from one location to another.
1950's- Barbara McClintock, "Jumping Genes" half of human chromosome is transposon-associated |
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What is transposition?
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Movement of transposon.
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What is transposase?
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Enzyme that promotes transposition.
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3 things about bacterial transposons.
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Some are smal ~1 kb in length. others can be quite long.
Antibiotic resistance Contatin inverted repeats on ends. |
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What are two methods to analyze the transcriptional activity of a promoter?
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1.) Transcriptional fusion
2.) Translational fusion |
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What are the steps in transcriptional fusion?
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*Use plasmids with reporter genes (gfp, lacZ, luxCDABE).
*Remove toxin promoter, place upstream of reporter gene. (reporter gene contains own Shine-Delgarno). *Only measures promoter strenth and activity |
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What are the steps in translational fusion?
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*Remove toxin promoter along with Shine-Delgarno and nucleotides encoding 1st couple of amino acids of toxin.
*Fuse in frame with gfp *Measures strength of promoter and effect of translation |
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What are the 4 components involved in transcriptional Regulation?
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* RNA polymerase
* Promoter * Shine-Delgarno * Regulatory proteins |
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What are operons?
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Genes that are transcribed from same promoter and controlled by the same regulatory sites.
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What is a regulon?
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A set of genes (or operons) expressed (transcribed) from separate promoters, but controlled by the same regulatory molecule. Sigma factors.
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What are transcription factors?
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DNA binding protein that associate with or at promoters. Goal is to increase or decrease transcription.
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What is a repressor? What is an activator?
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Transcription factors that repress transcription. Transcription factors that activate transcription. Some transcription factors can be both repressors and activators.
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Where do transcription factors often bind?
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Inverted repeat DNA sequences that are in promoter regions. Binding sequences are called operators.
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How does maltose utilization in E. coli work in presence of maltose?
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Transcriptional activator binds to the sequence overlapping the -35 of promoter.
Transcriptional regulator recruits RNAP. Transcriptional regulator and maltose serve as the -35. high transcription! |
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How does maltose utilization in E. coli work in absence of maltose?
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Without maltose, promoter is very weak sigma 70.
-35 is not consensus. Low transcription. |
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How do arginine biosynthetic genes work in presence of arginine?
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Has very good sigma 70 promoter, but in presence of arg:
transcriptional repressor binds to operator, transcription is repressed. |
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How do arginine biosynthetic genes work in absence of arginine?
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Has very good sigma 70 promoter. When no arg, transcriptional repressor is not bound.
High transcription. |
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Where do activators usually bind?
Where do repressors usually bind? |
over or upstream of -35
Downstream of -35. (-15 downstream) |
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How do repressors work?
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stop transcription after it begins
prevent RNAP from binding the promoter. |
