Midterm #1 material

Question 1

What is an auxotroph

Answer 1

Unable to create all of its own nutrients from elemental substrates

Question 2

What frequency does spontaneous mutants happen in?

Answer 2

10^-10 to 10^-9 for any phenotype

Question 3

What makes mutants independent strains?

Answer 3

If one isolates a single mutant colony from each culture

Question 4

What constitutes sibling mutant strains?

Answer 4

If one isolates more than one mutant colony from any single culture

Question 5

What is selection?

Answer 5

Direct isolation

Question 6

Why is selection beneficial?

Answer 6

You’re able to grow under restrictive conditions that select against the parental strain

Question 7

In Screening, how do you transfer cells from mutant colonies?

Answer 7

Patching, replica plating to a variety of other media

Question 8

What are the conditions for Screening?

Answer 8

Non-selective, permissive

Question 9

What are the compounds required for biosynthesis that auxotrophic mutants cannot synthesize?

Answer 9

Amino acids, nucleotides, vitamins

Question 10

What type of mutants are auxotrophs? What is the result of their characteristic?

Answer 10

• Biosynthetic/anabolic mutants
• Will fail to grow on minimal media regardless of carbon source

Question 11

What are Catabolic mutants unable to do?

Answer 11

Break-down compounds supplied as a source of carbon/energy

Question 12

What can you deduce from the appearance of auxotrophic phenotypes?

Answer 12

The mutagenesis was successful

Question 13

How do you calculate transposition frequency?

Answer 13

Divide mutants/ml by recipients/ml

Question 14

How do you increase mutation rate because the spontaneous mutation rate is too low?

Answer 14

Add mutagenic agent like chemical (EMS, NTG) or physical (UV)

Question 15

How do you optimize probability of isolating desired mutants?

Answer 15

Following a chemical or physical mutagenesis procedure with an Enrichment step

Question 16

What type of synthesis does penicillin-type antibiotics interfere with?

Answer 16

Peptidoglycan

Question 17

What do Penicillin only kill?

Answer 17

Actively growing/dividing cells

Question 18

What do Penicillin not kill?

Answer 18

Non-growing cells

Question 19

What does Penicillin do to mutants under restrictive conditions?

Answer 19

Kill them

Question 20

What do nutrients released from killed cells allow?

Answer 20

Mutants to grow under restrictive conditions and be killed by penicillin

Question 21

Where can Penicillin enrichment only be done?

Answer 21

On liquid tubes not solid plates

Question 22

What is Auxanography?

Answer 22

A way to identify nutrient requirement of auxotrophic

Question 23

What is an auxotroph?

Answer 23

Strains that fail to grow because a nutrient they are unable to biosynthesize is missing from a medium

Question 24

What are prototrophs?

Answer 24

Are able to biosynthesize all nutrients from C, N, P

Question 25

What do mutations in any of the lac genes characteristically result in?

Answer 25

A lactose utilization phenotype

Question 26

What is a mutation?

Answer 26

Change in the genetic code relative to the wild type or parental strain

Question 27

What are examples of a mutation?

Answer 27

Base pair changes, insertions, deletions, rearrangements

Question 28

What is a mutant?

Answer 28

An organism carrying a mutation(s)

Question 29

What is Isogenic strains?

Answer 29

Has the same genetic background and

Question 30

What are forward mutations?

Answer 30

Wild-type to mutant genotype

Question 31

What are reversion mutations?

Answer 31

Mutant to wild-type genotype

Question 32

What are Absolute Defective Mutations?

Answer 32

Same phenotype under all conditions and same phenotype in presence of other mutations

Question 33

What are Conditional mutations?

Answer 33

Phenotype depends upon conditions or presence of other mutation

Question 34

What are suppressor-sensitive mutations?

Answer 34

Mutations where the OG mutation puts a stop codon where a stop codon shouldn't be

Question 35

What are specific examples of nonsense mutations?

Answer 35

Amber (Am), Opal (Op), and Ochre (Oc)

Question 36

What does Temperature Sensitive mean?

Answer 36

Mutant phenotype at restrictive temperature

Question 37

What are frameshift mutations?

Answer 37

Insertion or deletion of a number of nucleotides that is not a multiple of 3 within the translated portion of gene

Question 38

What are transitions?

Answer 38

Base change from a purine to another purine, or a pyrimidine to another pyrimidine

Question 39

What is the make up of a purine?

Answer 39

A,G: Double ring

Question 40

What is the make up of a pyrimidine?

Answer 40

T (U), C: single ring

Question 41

What are transversions?

Answer 41

Base change from purine to pyrimidine

Question 42

What is a silent mutations?

Answer 42

Mutated codon encodes the same amino acid as the wild-type codon

Question 43

What are Neutral mutations?

Answer 43

Mutated codon encodes a different but functionally-similar amino acid

Question 44

What is a missense mutation?

Answer 44

Mutated codon encodes a different amino acid

Question 45

What is a nonsense mutation?

Answer 45

Mutated codon is a translational stop signal

Question 46

How many start codons are there?

Answer 46

6

Question 47

How many stop codons are there?

Answer 47

3

Question 48

What are the examples of start codons?

Answer 48

AUG (methionine), GUG (Valine), UUG (Leucine)

Question 49

What are the codons for the Ribosomal Binding site?

Answer 49

AGGA

Question 50

What do wobble allows for?

Answer 50

tRNAs to insert an amino acid into a growing peptide chain

Question 51

What is intragenic suppression?

Answer 51

Suppressor mutation occurring in the same gene as the first mutation

Question 52

What is extragenic suppression?

Answer 52

Suppressor mutations within a different gene