4. microbial genetics Flashcards
the basic unit of heredity; a segment of DNA that encodes for a gene product (polypeptide, protein or RNA)
gene
is the entire set of DNA instructions found in a cell. contains all the information needed for an individual to develop and function. consists the coding regions of DNA and non coding regions
genome
this is the genetic material found in the cell passed through generations
genotype
what are some examples of genotypes found in the cell?
plasmid, chromosomes
this is the observable characteristic or traits of an organism
phenotype
what are some examples of phenotypes found in the cell?
flagellum, cell wall, pili, proteins, capsule
T/F: transcription and translation occur in the same area in a prokaryotic cell
true - both occur in cytoplasm because prokaryotic cell doesn’t have a nucleus
T/F: transcription and translation occur in the same area in a eukaryotic cell
false
transcription - nucleus
translation - cytoplasm
what is the product and reactant of transcription?
DNA -> mRNA
the mRNA (referred to as ssRNA) is transcribed as the RNA complement to the coding DNA strand
what enzyme catalyzes transcription?
RNA polymerase
_____ is performed by ribosomes in the cytoplasm of the cell
translation
____- participates in translation (polypeptide synthesis) by transferring the amino acids from the cytoplasm to the ribosomes and binding them to the peptide chain according to the mRNA codons
tRNA (transfer RNA)
these two types of RNA tend to be stable and together account for more Ethan 95% of the total RNA in a bacterial cell
rRNA and tRNA
____ eukaryotic cells contain two homologous of each chromosome
diploid
the gene which does not achieve phenotypic expression in the precedes of its homologue is ______
recessive
the gene that overrides the effect of its homologue is ____
dominant
region that resides within a gene but does not remain in the final mature mRNA molecule following transcription of that gene and does not code for amino acids that make up the protein encoded by that gene; found only in eukaryotes
introns
som eukaryotes, such as yeast, contain _______ - additional circular genetic materials that independently replicate
plasmids or episomes
most _____ genomes consist of a single circular DNA molecule chromosome
prokaryotic
a few bacteria have two chromosomes. what are some examples?
- brucella melitensis
- burkholderia pseudomallei
- vibrio cholerae
some bacteria have linear chromosomes, not circular. what are some examples?
- acintomycetes
- mycobacteria
bacterial genes are _____ (haploid/diploid)
haploid
many bacteria contain additional genes on _______. these are not important for the life of bacteria, they just give extra characteristics to the bacteria
plasmids
in contrast to eukaryotic genomes, 98% of bacterial genomes are __________ (coding/noncoding) sequences
coding
T/F: genes essential for bacterial growth and reproduction are carried on the plasmid
false - carried on the bacterial chromosome found in the core part of the chromosome
these structures of the prokaryotic genome are double-stranded DNA molecules that can exist and replicate independently. some of these can integrate into the hosts chromosome. they are NOT required for bacterial growth or reproduction.
plasmids
plasmids carry genes that give their host a selective advantage. list these four advantages
- render bacteria drug-resistant
- give them new metabolic abilities
- make them pathogenic
- provide them with other properties
plasmids mediate their transfer from one organism to another through _____ and ______ formation
conjugation and sex pili
plasmids are responsible for properties that can spread throughout a bacterial population such as _________
drug resistance - plasmids can move from antibiotic resistant bacteria to non-antibiotic resistant bacteria
these are distinct genetic elements on the chromosomes of a large number of bacterial pathogens; they encode various virulence factors and are normally absent from non-pathogenic strains of the same closely related species
pathogenicity islands (PAIs)
what are some characteristic of PAI’s?
- they have a different guanine + cytosine content from the rest of the genome of that bacteria
- they are closely linked on the chromosome to tRNA genes
- they are flanked by different repeats: allows the PAIs to be copied and inserted at a different locating of the genome
- they contain diverse genes important for pathogenesis, including antibiotic resistance, adhesions, invasions, exotoxins, and genes involved in genetic mobilization
these are a class of genetic elements that can move or “jump” to different locations within a genome; they are always integrated into the genome (chromosomes or plasmids) and can not replicate by themselves. They eventually become inactive and no longer move overtime
transposons
these are the simplest transposable elements which are found in almost all bacteria, viruses and some eukaryotes.; they create insertion mutations
insertion sequences elements (IS)
these are elements that could have antibiotic resistance or toxins genes
composite transposons
DNA replication in prokaryotes:
the replication off bacterial DNA begins at one point (oriC) and terminates in a region called ter. Does it move in one direction or both directions?
both directions - bidirectional replication
during DNA replication in prokaryotes, the two old strands of DNA are separated and used as templates to synthesize new strands. this is called:
semiconservative replication
during semiconservative replication, the structure where the two strands are separated is referred to as the ____________
replication fork
this is a large protein complex that carries out DNA replication in prokaryotes and has several enzymatic activities (DNA polymerases I, II and III)
replisome
these are enzymes that alter the supercoiling of dsDNA, by cutting the DNA to relax the oil and extend the DNA molecule
topoisomerases (DNA gyrase)
____________ are the targets of antibiotics e.g. quinolones - therefore DNA replication will not occur
topoisimerases
what are the two mechanisms of gene transfer?
- vertical gene transfer
- horizontal gene transfer
this is the vertical inheritance of parental genes to the progeny cells (offspring)
vertical gene transfer
this is where DNA can be transferred from one organism to another, for e.g. to another bacteria; the DNA can be stably incorporated into the recipient, permanently changing its genetic composition
horizontal gene transfer
what are the three mechanisms that mediate horizontal gene transfer?
- conjugation
- transduction
- transformation
mechanism that mediates HGT:
this mechanism requires donor cell-to-recipient cell contact to transfer only one strand of DNA. the recipient completes the structure of dsDNA by synthesizing the strand that complements the strand acquired from the donor.
conjugation
_____ are most frequently transferred by conjugation
plasmids
in conjugation, these are responsible for the formation of sex pilus and the extracellular multimeric proteins that attach donor cells to recipient cells; some of these can mobilize other plasmids of portions of the chromosome for transfer
fertility factors or self-transmissible plasmids (have tra genes)
mechanism that mediates HGT:
this is a phage (virus) mediated genetic recombination in bacteria. the phages infect bacterial cells and propagate inside them. when they leave the cell to infect other cells, they take some bacterial genes with them
transduction
mechanism that mediates HGT:
this is the direct uptake of extracellular “naked” DNA by the recipient cell; this process can be natural of forced.
transformation
