©SIRJOEL EXAM SOLUTIONS
10/3/2024 9:54 PM
Brock Biology of Microorganisms - Chapter
11 Exam Study Guide.
Mutation - answer✔heritable change in DNA sequence that can lead to a change in phenotype
(observable properties of an organism)
wild-type strain - answer✔-typically refers to strain isolated from nature
-this adjective for a strain can also refer to just one gene
mutant - answer✔-a cell of virus derived from wild type that carries a nucleotide sequence
(genotype) change
-observable properties (phenotype) may also be altered
-can be obtained from parental strain derived from wild-type
genotype - answer✔-designated by italicized letters (three lowercase + capital letter) for a gene
(ex. hisC)
phenotype - answer✔-designated by capital letter + two lowercase letters and +/- to indicate
presence/absence (ex. His+ or His-)
isolation of mutants - answer✔styles are screening (nonselectable) versus selection (selectable)
selectable mutations - answer✔-makes isolation advantageous
-changing environmental conditions can allow progeny to outgrow and replace parent
-powerful genetic tool
-Ex. antibiotic resistance
nonselectable mutations - answer✔-does not make isolation advantageous
-can still lead to a phenotypic change
-requires time-consuming screening
, ©SIRJOEL EXAM SOLUTIONS
10/3/2024 9:54 PM
-Ex. color loss in pigmented organism
isolation of nutritional auxotrophs - answer✔-use replica plating screening for isolation
-has an additional nutritional requirement for growth (ex. His-)
replica plating - answer✔-screens for nutritionally defective mutants
-transfer colonies from master plate
-inability of colony to grow medium lacking a nutrient indicates mutation?
-colony on master plate is picked, purified, and characterized
prototroph - answer✔parental strain (ex. His+)
spontaneous mutation - answer✔-mutations that occur without external intervention
-most result from occasional errors by DNA polymerase during replication
induced mutation - answer✔-mutations made environmentally and deliberately
-can result from exposure to natural radiation or chemicals that chemically modify DNA
point mutations - answer✔-mutations that change only one base pair
-can lead to single aa change in a protein, and incomplete protein, or no change at all
base-pair substitutions - answer✔missense, nonsense, and silent mutations
silent mutations - answer✔base-pair mutations that do not affect sequence of encoded
polypeptide or phenotype (almost always third base of codon)
missense mutation - answer✔-base-pair mutations that change sequence of aa in polypeptide
-if at a critical locations, especially active site, could alter activity
-does not always lead to dysfunction
nonsense mutation - answer✔-base-pair mutation that leads to stop codon
-typically results in truncated (incomplete) protein that lacks normal activity
truncated protein - answer✔an incomplete protein (as a result of nonsense mutation)
transitions - answer✔base-pair mutations where purines are substituted for purines (or
pyrimidines substituted for pyrimidines)
10/3/2024 9:54 PM
Brock Biology of Microorganisms - Chapter
11 Exam Study Guide.
Mutation - answer✔heritable change in DNA sequence that can lead to a change in phenotype
(observable properties of an organism)
wild-type strain - answer✔-typically refers to strain isolated from nature
-this adjective for a strain can also refer to just one gene
mutant - answer✔-a cell of virus derived from wild type that carries a nucleotide sequence
(genotype) change
-observable properties (phenotype) may also be altered
-can be obtained from parental strain derived from wild-type
genotype - answer✔-designated by italicized letters (three lowercase + capital letter) for a gene
(ex. hisC)
phenotype - answer✔-designated by capital letter + two lowercase letters and +/- to indicate
presence/absence (ex. His+ or His-)
isolation of mutants - answer✔styles are screening (nonselectable) versus selection (selectable)
selectable mutations - answer✔-makes isolation advantageous
-changing environmental conditions can allow progeny to outgrow and replace parent
-powerful genetic tool
-Ex. antibiotic resistance
nonselectable mutations - answer✔-does not make isolation advantageous
-can still lead to a phenotypic change
-requires time-consuming screening
, ©SIRJOEL EXAM SOLUTIONS
10/3/2024 9:54 PM
-Ex. color loss in pigmented organism
isolation of nutritional auxotrophs - answer✔-use replica plating screening for isolation
-has an additional nutritional requirement for growth (ex. His-)
replica plating - answer✔-screens for nutritionally defective mutants
-transfer colonies from master plate
-inability of colony to grow medium lacking a nutrient indicates mutation?
-colony on master plate is picked, purified, and characterized
prototroph - answer✔parental strain (ex. His+)
spontaneous mutation - answer✔-mutations that occur without external intervention
-most result from occasional errors by DNA polymerase during replication
induced mutation - answer✔-mutations made environmentally and deliberately
-can result from exposure to natural radiation or chemicals that chemically modify DNA
point mutations - answer✔-mutations that change only one base pair
-can lead to single aa change in a protein, and incomplete protein, or no change at all
base-pair substitutions - answer✔missense, nonsense, and silent mutations
silent mutations - answer✔base-pair mutations that do not affect sequence of encoded
polypeptide or phenotype (almost always third base of codon)
missense mutation - answer✔-base-pair mutations that change sequence of aa in polypeptide
-if at a critical locations, especially active site, could alter activity
-does not always lead to dysfunction
nonsense mutation - answer✔-base-pair mutation that leads to stop codon
-typically results in truncated (incomplete) protein that lacks normal activity
truncated protein - answer✔an incomplete protein (as a result of nonsense mutation)
transitions - answer✔base-pair mutations where purines are substituted for purines (or
pyrimidines substituted for pyrimidines)
