Chapter 10-Genetics

Question 1

Mutation

Answer 1

Heritable change in the base sequence of the genome of an organism

Question 2

Mutant

Answer 2

Organism with a mutation, genotype differs from parents

Question 3

Wild-type

Answer 3

Isolated from nature, can be gene or strain

Question 4

What are some examples of genotype vs. phenotype? How do these examples relate to mutations?

Answer 4

The gene for histodinol phosphate aminotransferase, hisC codes for the protein HisC. Mutations in this gene are hisCI and hisC2
His+ and His- do different actions

Question 5

What does His+ do?

Answer 5

Makes own histodine (histodine prototroph)

Question 6

What does His- do?

Answer 6

Cannot make own histidine, requires histidine supplement (histidine auxotroph)

Question 7

Mutant selection

Answer 7

Placing organisms under conditions that favor or inhibit growth of cells with certain phenotypes

Question 8

Mutant screening

Answer 8

Procedure to evaluate many strains, but all strains are able to grow

Question 9

Is antibiotics resistance selectable or screening?

Answer 9

It’s selectable

Question 10

Is pigment production selectable or screening?

Answer 10

Must screen

Question 11

What are two molecular bases for mutation?

Answer 11

1. Induced-environmental cause

2. Spontaneous-errors in DNA replication

Question 12

Transition

Answer 12

a point mutation that changes a purine nucleotide to another purine (A ↔ G) or a pyrimidine nucleotide to another pyrimidine (C ↔ T).

Question 13

Transversion

Answer 13

the substitution of a (two ring) purine for a (one ring) pyrimidine or vice versa, in deoxyribonucleic acid (DNA).[1]

Question 14

Frameshifts are due to what?

Answer 14

Due to insertions or deletions

Question 15

Reversion

Answer 15

“Back mutation” that restores the original phenotype

Question 16

Same-site revertant

Answer 16

Mutation at same site restores phenotype

Question 17

Second-site revertant

Answer 17

Mutation at different site in DNA restores phenotype-supressor mutation

Question 18

Supressor mutations

Answer 18

• Mutations in same gene (2nd frameshift mutation)
• Mutation in another gene that restores function
• Mutation in another gene that replaces non-functional enzyme with a functional one

Question 19

Deletions, frameshift mutations are…

Answer 19

stable

Question 20

Insertions are…

Answer 20

not as stable

Question 21

What is removed during direct reversal during DNA repair?

Answer 21

An alkyl group

Question 22

What are three ways of DNA repair?

Answer 22

1. Direct reversal
2. Repair of single-stranded damage
3. Repair of double-strand damage

Question 23

In addition to the removal of an alkyl group, what also happens during direct reversal?

Answer 23

Photoreactivation, which cleaves pyrimidine dimers

Question 24

What is repaired during repair of single-strand damage?

Answer 24

Base excision and nucleotide excision

Question 25

How does double-strand damage repair work?

Answer 25

Through recombination to repair

Question 26

What is repaired during double-strand repair?

Answer 26

Cross-strand links and double-stranded break

Question 27

Describe the rate of changes in mutation.

Answer 27

It is low, yet detectable.

Question 28

What organism has enhanced DNA repair?

Answer 28

Deinococcus radiodurans

Question 29

In what ways does Deinococcus radiodurans have enhanced DNA repair?

Answer 29

20x resistant to UV | 200x ionizing radiation

Question 30

What can cause an increased mutation rate?

Answer 30

Mutator strains in changing environments

Question 31

What is the Ames Test?

Answer 31

It is a mutagenicity test for carcinogens.

Question 32

What does the Ames Test test for?

Answer 32

It tests for mutagenic chemicals.

Question 33

How does the Ames Test work?

Answer 33

It uses auxotrophs with point mutations so that reversion can occur (His-S. enterica or Trp- E.coli). Also, back mutants have colonies formed on minimal medium and they form more in presence of mutagen

Question 34

Improvements to the Ames test

Answer 34

- Strains that use error-prone repair pathways don't always give the best reading. - Liver enzyme preparations to convert chemicals to active forms needs work.

Question 35

What are 5 kinds of gene transfer?

Answer 35

1. Recombination 2. Transformation 3. Conjugation 4. Transduction 5. Transposable elements

Question 36

Recombination

Answer 36

DNA from two different sources exchange sections or are brought together into a single DNA molecule

Question 37

What is formed by recombination?

Answer 37

Homologous DNA

Question 38

How does recombination take place?

Answer 38

Crossing over

Question 39

Transformation

Answer 39

Free DNA from the environment transforms competent cells

Question 40

First discovery of transformation was by...

Answer 40

Frederick Griffith in 1928

Question 41

Transformtion

Answer 41

Free DNA from the environment transforms competent cells

Question 42

Transduction

Answer 42

Bacteriophage transfers DNA from one cell to another

Question 43

Generalized transduction

Answer 43

Any gene on donor chromosome can be transferred

Question 44

Specialized transduction

Answer 44

Only a specific set of bacterial genes are transferred due to mistakes in excision

Question 45

Conjugation

Answer 45

Genetic exchange involving cell-to-cell contact

Question 46

An F plasmid stands for

Answer 46

fertility

Question 47

What can an F plasmid do?

Answer 47

Can synthesize F pilus and make able the mobilization of DNA for transfer

Question 48

How is the uptake of another F plasmid prevented?

Answer 48

Alteration of surface receptors

Question 49

Episome

Answer 49

plasmid that can integrate into the chromosome

Question 50

F+ strain

Answer 50

nonintegrated plasmid

Question 51

Hfr strain

Answer 51

plasmid integrated into genome

Question 52

Why is gene transfer system development difficult in Archaea?

Answer 52

Due to extreme conditions and antibiotics are useless

Question 53

What kind of gene transfer happens in Archaea?

Answer 53

Transformation, conjugation, and transduction

Question 54

Mobile DNA, aka

Answer 54

transposable elements

Question 55

Transposable elements

Answer 55

DNA that moves from one site to another within a DNA molecule

Question 56

What are the insertion sequences of transposable elements like?

Answer 56

Short, 1000 nucleotides, inverted repeated of 10-50 base pairs

Question 57

What protein is involved in the insertion sequence formation in transposable elements?

Answer 57

Transposase

Question 58

Describe transposons.

Answer 58

Large Inverted repeats Transposase Other genes

Question 59

Transposon mutagenesis

Answer 59

Selection and screening of treated colonies follow