Microbial Genetics

Question 1

prokaryotic genome

Answer 1

• circular
• dna in nucleoid
• haploid
• no introns
• single
• contains plasmids

Question 2

eukaryotic genome

Answer 2

• linear
• nucleus
• diploid or haploid
• mulltiple

Question 3

bacterial gene expression

Answer 3

transcription and translation both occur in the same location in the cytoplasm and at the same time

Question 4

eukaryotic gene expression

Answer 4

Transcription occurs in the nucleus, translation in the cytoplasm
-RNA must be processed before translation

Question 5

lac operon

Answer 5

• inducible operon
• inducer: allolactose
• allolactose binds to the repressor and decreases the repressors affinity for the operator

Question 6

arginine operon

Answer 6

• constitutively active and repressible
• under control of repressor ArgR
• if Arg accumulates it binds to the repressot to activate it
• the repressor than can’t bind to the operator and blocks transcription

Question 7

when there is low cAMP and high glucose, the lac operon:

Answer 7

weak expression of the lac operon

Question 8

when there is high cAMP and low glucose, the lac operon

Answer 8

CAP can bind to cAMP and enhance lac operon expression

Question 9

sigma factor

Answer 9

subunit loosely attached to RNA pol that recognizes a promoter

Question 10

how is genetic variation introduced into bacteria

Answer 10

• mutation passed down from parents to progeny

- horizontal gene transfer

Question 11

point mutation

Answer 11

• most common

- single nucleotide change

Question 12

spontaneous mutation

Answer 12

arise during normal DNA replication; mutations can be passed to progeny

Question 13

induced mutations

Answer 13

caused by exposure to mutagens (physical or chemical)

Question 14

silent mutations

Answer 14

no change in AA sequence

Question 15

missense mutation

Answer 15

slightly different AA sequence

Question 16

nonsense mutation

Answer 16

polypeptide synthesis ceases

Question 17

frameshift mutation

Answer 17

major difference in AA sequence

Question 18

Radiation effect on DNA

Answer 18

X-rays: single and double stranded DNA breaks (often lethal)

UV: thymine dimers

Question 19

alkylating agents

Answer 19

• change base pairing properties

* increase chance of incorrect nucleotide incorporation

Question 20

base analogs

Answer 20

resemble bases, but have different H bonding properties

Question 21

intercalating agents

Answer 21

flat molecules that insert into DNA

-cause addition or deletion of single base during replication –> frameshift mutation

Question 22

temperate phage

Answer 22

Ability to display a lysogenic life cycle

• can integrate genome into their host bacteriums chromosome
• can also undergo a lytic life cycle

Question 23

lytic phage

Answer 23

results in destruction of the infected cell and its membrane

Question 24

plasmids

Answer 24

• have origins of replication
• can replicate independently of the chrom
• can have a high or low copy number
• most frequently transferred via conjugation

Question 25

transposable elements

Answer 25

mobile segments of DNA that transpose themselves from one location to another in the SAME cell
-non homologous recombination

Question 26

restriction endonuclease

Answer 26

recognize specific nucleotide sequences and cleave the DNA at those specific sites

Question 27

Transformation

Answer 27

• Naked DNA in solution is taken up by the cell
• Inhibited by DNAse
• Demonstrated in streptoc. pneum
• homologous recombination to enter into DNA

**Cell must be competent

Question 28

Transduction

Answer 28

Process by which bacterial viruses (phages) transfer bacterial genes from a donor to a recipient

Question 29

Generalized Transduction

Answer 29

lytic bacteriophage

Question 30

Specialzied Transduction

Answer 30

Temperate bacteriophage

Question 31

temperate phages

Answer 31

• integrate into bacterial chromosome

- must be excised to enter lytic life style

Question 32

Generalized Transduction steps

Answer 32

1. phage attaches and enters cell
2. Phage cuts bacterial DNA into pieces and phage nucleic acid is replicated
3. Transducing particle carries bacterial DNA instead of phage DNA
4. Transducing particle attaches to a recipient cell
5. bacterial DNA is injected into the cell

Question 33

specialized transduction

Answer 33

1. temperate phage injects its DNA into the cell
2. phage DNA integrates into the host at specific site
3. prophage excised from bacterial chromosome, mistake made, some bacterial DNA flanking the phage is taken and phage DNA left behind

Question 34

conjugation

Answer 34

• Genetic transfer via direct contact
• F+ cell with origin of transfer conjugates to F- cel
• transfer of F plasmid
• sometimes not the full chromosome is able to transfer over

Question 35

Transposable elemnts

Answer 35

Integrate into new location through non-homologous recombination

Question 36

Transposable elements

Answer 36

Insertion sequences: simplest, inverted repeats, transposase gene

Transposans: contain gene for transposase and other

Question 37

lentivirus

Answer 37

type of retrovirus modified to be non-pathogenic

-viral DNA integrates randomly into the host chrom and introduces a gene that expresses protein

Question 38

adenovirus

Answer 38

• modified to be non-pathogenic creating a recombinant virus
• does NOT integrate into host genome