Genetics PPT 2

Question 1

Bacteria use three different mechanisms to adapt to

changing environments

Answer 1

Natural Selection
Mutation
Gene transfer

Question 2

A genetic change alters an organism’s

Answer 2

genotype

Question 3

a genetic change in bacteria can have a profound impact on bacteria because they are

Answer 3

haploid

Question 4

A change in genotype can easily alter the observable

characteristics of an organism

Answer 4

phenotype

Question 5

stable heritable changes in the base

sequence of DNA

Answer 5

mutations

Question 6

mutations can occur due to (3)

Answer 6

 Base substitutions
 Removal or addition of nucleotides
 Transposable elements

Question 7

how can mutations occur

Answer 7

spontaneously or be induced through the

use of a mutagen

Question 8

occur in natural environment

Occur infrequently and randomly

Answer 8

spontaneous mutations

Question 9

the probability that a mutation will be observed in a

given gene each time the cell divides

Answer 9

rate of mutation

Question 10

how are mutations classified

Answer 10

in terms of their effect on phenotype

Question 11

change colonial or cellular morphology

Answer 11

morphological mutations

Question 12

kill the organism

Answer 12

lethal mutations

Question 13

expressed only under certain conditions (e.g.,

high temperature)

Answer 13

conditional mutations

Question 14

changes in metabolic capabilities

auxotrophs vs prototrophs

Answer 14

biochemical mutations

Question 15

have mutations in biosynthetic pathways
 cannot synthesize product of pathway
 require product of pathway as nutrient in minimal
growth media

Answer 15

auxotrophs

Question 16

grow in minimal media without supplements

Answer 16

prototrophs

Question 17

resistance to pathogen, chemical, or antibiotic

Answer 17

resistance mutations

Question 18

 Most common type of
mutation
 Result from mistakes
during DNA synthesis

Answer 18

base substitutions

Question 19

Occur when one base pair is changed

Answer 19

point mutations

Question 20

• Results from a nucleotide change that generates a codon which still specifies the wild type amino acid

Answer 20

silent mutation

Question 21

Mutations resulting from nucleotide substitution leading

to a change in the amino acid incorporated into the protein

Answer 21

missense mutation

Question 22

Mutations that change an amino acid codon to

a stop codon

Answer 22

nonsense mutation

Question 23

Deletion or addition of nucleotide base pairs (Shifts the codons)
Alters reading frame
Affects all amino acids downstream from addition or deletion

Answer 23

frameshift mutations

Question 24

• changes in regulatory sequences

* alter control of gene expression

Answer 24

regulatory mutations

Question 25

can disrupt protein synthesis

some tRNA mutations are suppressor mutations

Answer 25

rRNA and tRNA mutations

Question 26

Special segments of DNA that move spontaneously

from gene to gene

Answer 26

Transposable Elements

Question 27

disrupt proper function of gene into which they insert

Answer 27

transposons

Question 28

Mutations can be intentionally produced to
demonstrate function of particular gene or set of
genes

Answer 28

induced mutations

Question 29

what are the three ways to induce mutationsf

Answer 29

Chemical mutagens
Transposition
Radiation

Question 30

Gene that receives transposon will undergo an

insertion mutation

Answer 30

knock out mutation

Question 31

what are the two types of radiation

Answer 31

ultraviolet light and x rays

Question 32

Causes covalent bonding between adjacent thymine bases forming thymine dimers which distorts DNA

Answer 32

ultraviolet light

Question 33

 Cause breaks and alterations in DNA

• Breaks that occur on both strands are often lethal

Answer 33

x rays

Question 34

Largest group of chemical mutagens

Answer 34

Alkylating agents

Question 35

Chemicals that are structurally similar to the nitrogenous bases but have slightly altered base pairing properties

Answer 35

base analogs

Question 36

what do the base analogs include

Answer 36

5-bromouracil and 2 -aminopurine

Question 37

Planar molecules that insert themselves between adjacent bases (create space between bases)

Answer 37

Intercalating agents

Question 38

Cells developed two methods of repair

Answer 38

proofreading and post replication repair

Question 39

correction of errors in base pairing made during
replication
• DNA polymerase has this function
• Able to excise incorrect base and replace with
correct one

Answer 39

proofreading

Question 40

Corrects damage that causes distortions in double helix
• e.g., thymine dimers
• e.g., damaged bases

Answer 40

Excision Repair

Question 41

type of excision repair
Endonuclease removes short stretch of nucleotides
• DNA polymerase fills gap
• DNA ligase joins ends

Answer 41

mismatch repair

Question 42

Used by E. coli postreplication repair system to

distinguish old DNA strands from new DNA strands

Answer 42

DNA Methylation

Question 43

what DNA is methylated

Answer 43

old DNA methylated; new DNA not methylated

Question 44

what are the two repair mechanisms of thymine dimers

Answer 44

Photoreactivation and excision repair

Question 45

Removes the nitrogenous base without removing the sugar phosphate backbone

Answer 45

glycosylase

Question 46

Last ditch effort to bypass damage
 Inducible repair system
 Used to repair excessive damage that halts
replication, leaving many gaps
Produces new DNA polymerase

Answer 46

SOS repair

Question 47

finding mutants requires what

Answer 47

sensitive detection methods
• Direct selection
• Indirect selection

Question 48

Observation of changes in phenotype

 Involves inoculating population of bacteria on medium on which only mutants will grow

Answer 48

direct selection

Question 49

Used to detect auxotrophic mutants

Answer 49

indirect selection