Lecture 5: Bacterial Genetics Flashcards
What is a mutant
Offspring from a normal member of a species but genetically distinct from wild type
What is a mutation
Any heritable change in DNA sequence
What is an allele
Different forms of the same gene
What are isogenic strains
Two linages of the same bacterium that have a single change
Do mutations occur spontaneously or are they driven by selective pressures
Occur spontaneously but if you apply selective pressure you will create mutations that are resistant
What is selection
Growth condition that allows for growth of only a specific kind of mutant
What is a spontaneous base pair change
Occurring by insertion of incorrect base during replication
What is an induced base pair change
Addition of external factors (mutagens) that alter chemical bonds in DNA and need repair
What happens to base pairs with UV exposure
Form thymine dimer (T-T instead of T-A)
CCC encodes for ___
Proline
What is a silent or synonymous mutation and example
Change in base pair that doesn’t change coding of amino acid
CCC- encodes proline but so does CCA, CCG, CCU
What is a missense or nonsynonymous mutations
Changes in AA
CCU codes for proline but CGC codes arginine, GCC codes alanine
What is a null mutation
Loss of function of gene being altered
Does a nonsynonymous mutation always lead to a change in phenotype
No
Is mutation always beneficial to bacterium
No
How does transcription and translation occur in prokaryotes
Occurs simultaneously (CTT) because lack nucleus and nuclear membrane so mRNA is produced and ribosomes are immediately added
What is polycistronic
In prokaryotes there are multiple translation start sites, multiple genes controlled by one promoter
What is monocistronic
In eukaryotes single translation start site, 1 gene/1 promoter
Describe how transcription termination can occur with Rho
Rho binds rut sites that are not covered by ribosomes, progresses up to the mRNA strand until it hits RNA polymerase and dislodges it
Controls genes produced
What type of mutation is a mutation that changes from coding an amino acid to coding a stop codon- lead to early translation termination
Nonsense mutation
What are the two stop codons
UAG and UAA
What type of mutation can cause both early termination of transcription and translation
Non-sense mutation
What are frame shift mutations
Base deletions or additions that alter the reading frame of the mRNA
What is vertical gene transfer
DNA replication provides Daugherty cells with copy of parental DNA
What is horizontal gene transfer
Evolutionary process that distributes genes between divergent prokaryotic linages
What is transformation
Uptake of naked DNA from the environment and stable incorporation into genome
What is transduction
Transfer of DNA by virus or viral vector (bacteriophage)
What is transposition
Transposon genes are transferred from one organism to another through copying and insertion processes