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35 Cards in this Set

  • Front
  • Back
Do live S. pneumoniae cells with capsule kill mouse if injected?
How about heat treated and dead?
How about live, but no capsule?
How about both live with no capsule AND dead cells?
How was it discovered that DNA is the transforming material in bacteria?
-live cells lysed
-DNAases added to some, while others got Proteases
-both solutions injected into mouse
-mouse lived when DNA was destroyed, but died if only the proteins were destroyed
*no live cells recovered from live mouse
Why are bacteria ideal for genetic analysis?
-fast growth rate
-enormous numbers of offspring
-small and easily sequenced genomes
What are 4 types of DNA in bacterial cells?
What does chromosomal DNA do?
-carries genetic code
-circular extrachromosomal elements; replicate independently
-either infect and lyse host bacteria or integrate DNA into chromosome
-DNA that moves from one site to another
How many chromosomes do bacteria have?
Nucleic acid?
DNA location?
-one (rarely two)
-in some cells, frequently more than one per cell
-circular or linear dsDNA
-in nucleoid and in plasmids in cytosol
How many chromosomes do Archaea have?
Nucleic acid?
DNA location?
-in some cells
-circular dsDNA
-in nucleoid and in plasmids in cytocol
How many chromosomes do Eukarya have?
Nucleic acid?
DNA location?
-two or more (one exception)
-some fungi and protozoa
-Linear dsDNA in nucleus, circular dsDNA in mito, chloro, and plasmids
-in nuclei, and in mitochondria, chloro, and plasmids in cytosol
How does E coli package its chromosomal DNA? Why is this necessary?
-it has 4.4 x 10^6 base pairs equalling 1mm in length, but E coli is only 1 micron long!
How do linear chromosomes organize?
-nucleosomes that aggregate forming chromatic (and therfore introducing negative supercoils)
What are three types of supercoiling?
-twisting DNA
-positive or negative supercoiling
-negative supercoiling; tweisted opposite direction of right-handed helix
What are plasmids?
-circular extrachromosomal elements that are smaller than chromosomes
-replicate independently of chromosomes using the same mechanisms
-can move from organism to organism (mobilizatin which leads to increases in antibiotic resistance)
What are 6 functions that plasmids encode proteins with?
-antibiotic resistance
-antibiotic production
-toxins; virulence
-heavy metal resistance
-proteins that mediate plasmid transfer
What is plasmid R100 resistant to?
-chloramphenic mercury, sulfonamide, streptomyscin, tetracy
What is transposition?
-movement of peices of DNA from one site on a chromosome to another
-occurs in all organisms at low frequency (10^5-10^7 per generation)
-requires genetic element (transposable)
-movement and insertion into genes can inactivate function
What is transposon mutagenesis?
-powerful genetic tool to create mutations
What are three types of transposable elements that prokaryotes have?
-insertion sequences
-virus mu
What are insertion sequences (IS) in prokaryotes?
only contain the DNA information necessary to transpose
What are transpsons (Tn) in prokaryotes?
-contain addition genetic material besides the insertion information
What are virus mu in prokaryotes?
-double stranded DNA bacteriophage that inserts into host genes
What are Transposase enzymes?
-required for tansposition
-recognizes, cuts, and ligates DNA
-interacts with short inverted terminal repeats (IR) 20-1000 base pairs in length
What do many Tn elements contain?
-antibiotic and drug resistance genes
*this antibiotic resistance can move from cell to cell
What is semi-conservatative replication in DNA replication?
-one old strand and one new strand
How does the addition of new nucleotides proceed?
-in a 5' to 3' direction
What are DNA polymerases?
-enzymes that catalyze the addition of new nucleotides
-can NOT start a chain of nucleotides (need RNA primer)
What creates an RNA primer and what is it for?
-primase enzyme
-starting a chain of nucleotides for replication
What must happen to a double helix before it can be replicated?
-it must be unwound (helicase) and replication proceeds on both strands
How does replication occur in circular chromosomes?
-replication is bidirectional at replication forks
-results in theta structure
What type of replication occurs in the leading strand?
What type of replication occurs in the lagging strand?
-discontinuous replication and ligation of Okazaki fragments
What two types of strands are created in DNA replication?
-leading and lagging strands
What are the fragments called during DNA replication with lagging strands?
-Okazaki fragments
What do errors in DNA replication cause?
What stages allow for repair of mutations?
-durin replication when complementary base pairs are formed and during the proofreading (DNA polymerase cuts out wrong nucleotide
-after replication: several DNA repair mechanisms
When proofreading occurs during replication, what is used?
*I don't know what it's used for:
3'<--- 5' exonuclease activity