Ch.8 Microbial Genetics Flashcards
what is a phenotype?
functioning of proteins in a cell
how are genotype and phenotype connected?
connected through various RNA molecules
how do changes in genotype affect phenotypes?
changes in DNA result in differences in amino acid sequences and are protein detective
How is the genotype preserved?
through replication of DNA
What is the flow of information?
DNA->RNA->Protein
what determines the phenotypic trait?
the inherited genetic makeups of an organism
what kind of chromosome does the prokaryote genome have?
single circular chromosome
what is the inheritance of a prokaryote genome?
vertical and horizontal transmission of genes
1 step in gene expression
Retrieval of information:
*genetic code based on transcript
*Employs different RNAs
2 step in gene expression
Transcription:
*transcribe a gene
*RNA Polymers
*mRNA (transcript)
3 step in gene expression
Translation:
*Ribosomes(rRNA)
*Transfer RNA’s
transition & translation are coupled in what?
prokaryotes
what are mutations defined as?
permanent alterations of the DNA base sequence
mutation can be
silent (no effect)
Lethal (Kills)
Beneficial(evaluate in the context of what going to happen)
what is a mutation caused by?
chemicals
Radiation
Mutagens
what is spontaneous mutation?
random mistakes during replication
What is a missense mutation?
amino acid substitution
causes:
the loss of function or change of structure
what is a nonsense mutation?
premature stop codon forms
(lethal, bad/nonfunctional)
what is a frameshift mutation?
insertion or deletion of a single base
change in amino acid sequence following insertion/deletion site
What are the mechanisms of horizontal gene transfer?
Tranformation
Conjugation
Transduction
Transpotion
describe transformation
uptake of naked DNA from the environment
(comes into the cell)
describe conjugation
transfer of DNA via cell-to-cell contact (donor recipient) via sex pilus
physical contact between the cell usually passage of plasmid
describe transduction
DNA transfer via a viral intermediate
(virus )
describe transposition
transfer of transposons (mobile genetic elements)
what did Fredirck Griffith work with?
Streptococcus pneumoniae culture
what did Griffith discover?
transformation: the transfer of “naked” DNA from cell to cell in solution
describe the experiment by Fredrick Griffith
heat-killed virulent forms of S.pneumoniae lysed
cells released DNA
taken up by live non-virulent forms
what is competence?
cell envelope changes occur which enables the uptake of DNA
what is artificial transformation?
it is made to be competent via chemical treatment and electrical shock
what are plasmids?
small,extra-chromosomal circular segment of DNA
what is the size of plasmids?
2-25 kbp
how do plasmids replicate?
replicate autonomously
possesses own origin of replication(ori)
describe conjugative plasmids
are transferable, F (fertility) Factor
posses ori for conjunctive transfer
what can be found on plasmids?
catabolic genes
virulence genes
plasmids can transfer only if what?
if there is an F factor
The fertility factor(conjugative plasmid) has
donor F+
recipient F- cells
the recipient receiving an F factor may integrate it into its chromosome resulting
cell termed Hfr (high-frequency recombination) cell
conjugation of Hfr with F- cell:
replication and transfer of chromosome copy;
initiated within integrated F factor
conjugation of Hfr with an F- cell: the F- recipient cell remains as an F- following conjugation
the connection between cells is disrupted
the chromosome breaks & the F- factor is not transferred
The F- F-recipient cell acquires whatever genes are received prior to breakage and can express these
bacterial viruses (phages) serve as
The vehicle to transfer DNA between donor & recipient cells
what is generalized transduction?
any host genes can be transferred
what is specialized transduction?
only specific host genes are transferred (very restrictive)
Shiga
toxin
diphtheria toxin
cholera toxin
steps to generalized transduction:
- phage attachment
- Host DNA cleaved
- phage assembly; host DNA segments randomly package w/pahge carrying bacterial DNA
- Donor & recipient DNA recombine
what are transposons?
mobile genetic elements (700-40kbp long)
can move within chromosome
can move from cell to cell via
what is transposition?
transposons possess a transposase
the gene that recognizes specific inverted repeat sequences
simplest transposition:
insertion sequences (IS); have only transposase
complex transposition:
have transposase & other genes
Ex: antibiotic resistance
what does the Recall protein do?
mediates recombination between donor/recipient DNA
