bacterial genetics Flashcards
genome
genetic info in a cell, DNA
how may chromosomes do most bacteria have?
one
what is a gene?
segments of DNA that code for functional products
what are genomics?
sequence and molecular characterization of genome
what makes up a nucleotide?
- sugar
- base
- phosphate
what makes up a nucleoside?
sugar and base
what nitrogen bases are pyrimidine bases?
CTU
-cytosine, thymine, uracil
what nitrogen bases are purine bases?
AG
-adenine, guanine
what type of bonds hold nucleic acid pairs together?
hydrogen bonds
how many bonds hold G and C together?
3
how many bonds hold A and T (U) together?
2
which is more stable, GC or AT bonds?
GC
what is the primary structure of nucleic acids?
the sequence of the nucleotides in DNA or RNA
what are the secondary structures of nucleic acids?
intrastrand base pairing, observed in rRNA or tRNA
is RNA single or double stranded?
singe stranded
what are the three types of RNA?
mRNA, tRNA, rRNA
what is mRNA?
single-stranded and complementary to DNA (transcription)
what is tRNA?
translate genetic info
what is rRNA?
components of ribosome
What is denaturation (melting) of DNA?
separation of strands with breakage of H2 bonds
what is annealing of DNA?
coming together of two strands with formation of H2 bonds
what is hybridization of DNA?
formation of ds by complementary base pairings of two ss
what is DNA supercoiling?
- twisting of ds DNA
- allows packaging of strands of DNA in a cell
- neg or pos direction
- NEG is more common
what are topoisomerases?
-cause DNA to relax or supercoil
what does the topoisomerase, DNA gyrase do?
introduces negative strands
what does topoisomerase I do?
removes supercoiling
what does topoisomerase IV do?
unlinks the two circular molecules of DNA during replication
what are plasmids?
small molecules of DNA that replicate independent of the chromosome
what is the copy number of plasmids?
number of plasmids per cell
what is curing of plasmids?
loss of elimination of plasmids
what are the functions of plasmids?
carry gene codes for:
- antibiotic resistance
- virulence factors
- chemical resistance
- sex pili
- enzymes for environmental contamination
what are transposons?
transposable genetic elements or jumping genes
what do transposons do?
they are segments of DNA that can move from one site to another site on the same chromosome
-contain info for transposition (removal and instertion)
what cells have transposons?
prokaryotic and eukaryotic cells
-plays a role in genetic variation
what are the two types of transposons?
- insertion sequences: IS1, IS2, etc, contain a gene that codes for transposase
- transposons: Tn1, Tn2, etc, these are larger
T/F: transposons with antibiotic resistance can move resistance to other bacteria?
true
what are bacteriophages?
viruses that infect bacteria
what are the two types of baceriophages?
-lytic or lysogenic(temperate)
what is bactriophage immunity?
presence of prophage prevents infection by the same phage
what is phage conversion?
presence of prophage confers new properties
what is phage therapy?
the therapeutic use of lytic bacteriophages to treat bacterial infections
lytic phages are similar to what?
antibiotics
what is a mutation?
change in nucleotide base sequence that is inherited
what is genetic recomination?
genes from two different genomes are brought together
which brings about a larger change, mutation or recombination?
recombination
define horizontal gene transfer
from a donor cell to a recipient cell
define vertical gene transfer
mother to daughter cell
define mutant
an organism that carries mutation
define wild type strain
parental strain that existed in nature
define genotype desgnation
italicized gene encodes for a protein (?)
define phenotype designation
His+ or His-
what can cause spontaneous mutation?
- exposure to natural factors (oxygen radicals, etc)
- errors in base pairing during replication
what is point mutation?
change in one base pair - the phenotypic change depends on where the mutation occurs
what is a silent point mutation?
no phenotypic change
what is nonsense point mutation?
termination of protein synthesis
what is missense point mutation?
coding a different amino acid
what is a frameshift mutation?
insertion or deletion of a base pair results in reading frame shift
what is transposon mutagenesis?
mutation due to insertion of transposon (insertion sequence)
what is site directed mutagenesis?
mutation at a specific site or gee
what is genetic recombination?
physical exchange of genes between genetic elements
what are the three mechanisms of genetic recombination?
- transformation
- transduction
- conjugation
define transformation as a mechanism of genetic recombination
incorporation of free DNA into a recipient cell
a bacterium capable of being transformed is called what?
competent
define transduction as a mechanism of genetic recombination
DNA transfer is mediated by bacteriophage
what are the two methods of transduction
- generalized transduction
- specialized transduction
what is generalized transduction?
DNA from any portion of the host genome is transferred
what is specialized transduction
DNA from specific region of the host genome is transferred
what is conjugation as a mechanism of genetic recombination
DNA transfer is mediated by a cell to cell contact
-mediated by a conjugative plasmid from the donor cell
