Ch. 9 & Ch. 10 Flashcards
Wild-type/ Prototrophic Bacteria
Grow in minimal medium: they make all compounds they need
Auxotrophs
Grow in complete medium: contains what they need from growth and reproduction
Selective Medium
Lacks one essential nutrient
Episomes
plasmids capable of replicating freely and are able to integrate into bacterial chromosome
F (fertility factor)
Episome that controls mating/gene exchange between E coil cells
Conjugation
genetic material goes from one bacterium to another
Transformation
Bacteria takes DNA from medium
Transduction
Virus carries DNA to bacterium
Conjugation experiment by Lederberg and Tatum
Hey! these strains shouldn’t grow in this medium, but they do thanks to sharing of genes. And they need direct contact to make it happen.
F+ & F-
F+ x F-
F+ have sex pili and F factor. After giving it to F- cell, we have 2 F+ cells.
Hfr
f factor is part of the bacterial chromosome
Hfr x F-
A problem: the F- doesn’t like that it has an extra chromosome. So crossing over and degradation takes place. Technically no change (but some is possible due to crosses)
F’ Cell
Happens when Hfr cell has some internal crossing, we got the them separate, but not F+, because some of the genes that were on the main chromosome are on the F factor now.
F’ x F-
2x F’, but one of them has multiple copies of some genes.
Cells that can take up DNA through their cell membrane are said to be ___.
Competent
Transformation:
1. foreign DNA binds with complex
- Enzyme dissociates DNA to single strands
- Single-stranded fragment of DNA is imported into the cell
- DNA fragment recombines into a homologous region of the bacterial chromosome.
- Foreign DNA is duplicated with bacterial DNA after next round of cell division.
Cells that receive genetic material through transformation are called ____.
Transformants
Horizontal Gene Transfer
Bacteria take DNA from other species of bacteria and other organisms. (same species is vertical)
Bacterial Defense Mechanisms
- Virus must first attach to the cell wall or membrane and inject its DNA or RNA into the cell.
- Restriction Modification: restriction endonucleases that cleave viral DNA.
- CRISPR_Cas systems: immune system
Virus
Nucleic acid + protein coat
Phages that reproduce lytic cycle only
Virulent Phages
Phages that reproduce lysogenic or lytic cycle
Temperate phages
Inactive prophage
happens in lysogenic cycle.
Types of transduction:
- Generalized transduction
- Specialized transduction
- any gene may be transferred
2. only a few genes are transferred
Transducing phages
A piece of the bacterial chromosome, instead of phage DNA, occasionally gets packaged into a phage coat
Transductants
Bacterial genes can be moved from one bacterial strain to another, producing recombinant bacteria
Cotransduced
Only genes located close together on the bacterial chromosome will be transferred together
What are RNA viruses capable of integrating into the genomes of their hosts called? What must they produce?
Retroviruses
Reverse transcriptase- enzyme that can synthesize complementary DNA from either an RNA or DNA template.
Provirus
virual genome incorporated into an host chromosome
Retroviral genomes:
gag-
pol-
env-
gag- gene encodes proteins that make up the viral protein coat.
pol- encodes reverse transcriptase and enzyme called “integrase”, which inserts the viral DNA into a host chromosome
env- gene encodes the glycoproteins that appear on the surface of the viral envelop
oncogenes
in some retroviruses, may stimulate cell division and cause formation of tumors
Genetic Material must
- Periodically Mutates (vary)
- Encodes blueprint for proteins (phenotype)
- Replicates and transmits to progeny
Concentrations
A=T G=C
Nitrogenous bases are
CATG
Nucleotide
sugar phosphate base
Griffith’s Experiment
Mice, heat killed bad bacteria + good bacteria = dead mouse
Drs. Avery, Macleod, and McCarty’s experiment
DNase destroyed the transforming substance, the transforming substance must be DNA
The Hershey-Chase experiment
Virus Phages: DNA or protein? Used radioactive phosphorus (DNA) and sulfur (PROTEIN)
Fraenkel-conrat and singer’s experiment
RNA is the genetic material of TMV, RNA of one with protein of another
Deoxyribose vs. ribsoe
Ribose- OH attached to 2’ carbon atom
Deoxyribose: H at this position and 1 fewer oxygen atom
Why is DNA better suited as long term carrier of genetic info?
the addition oxygen atom on RNA makes it more reactive and less stable
DNA has double stranded structure, makes duplication more accurate
Purine
2 rings
AG
Pyrimdine
1 ring
CUT
Nucleosides
Sugar + Base
DNA: hydrogen bonds between pairs
noncovalent
2 between AT
3 between CG
CG pairing is stronger
phosphodiester linkages
strong covalent bonds, forms negatively charged backbone
connects 5’ phosphate group and 3’-OH group of adjoining nucleotides
Direction ALWAYS
5’ (phosphate) –> 3’ (hydroxyl group)
what else holds DNA together?
Stacked base pairs
Most DNA is in ___ form
B-Form: plenty of water, most stable, right handed helix, clockwise, 10 bp per 360 degrees.
A-form
if less water, right handed but shorter and wider, bases tilted away from main axis of the molecule.
Z-DNA
left handed. backbone zigzags.
Central Dogma
DNA replication –> TranSCRIPTion –> RNA –> TransLAtion –> Protein
Hair pin vs. stem
Hair Pin: Occurs when sequences of nucleotides on the same strand (single strand) are inverted complements.
Stem: stem but no loop
H-DNA
three-stranded (triplex); formed when DNA unwinds and one strand pairs with double-stranded DNA from another part of the molecule
Often occurs in long sequences of only purines or only pyrimidines
Common in mammalian genomes
DNA methylation
Methyl group to nitrogenous base. affects 3D structure and gene expression.
Watson & Crick & Franklin
10 bp
helix xhape
consistent diameter
