chapter 8 Microbial Genetics

Question 1

genetic change in bacteria:
What are the two methods?

Answer 1

mutation and horizontal gene transfer

Question 2

define what mutation is

Answer 2

is a change in the nucleotide sequence of DNA

it also may cause a change in a protein encoded by gene

Question 3

is a change in the nucleotide sequence of DNA, it also may cause a change in a protein encoded by gene

Answer 3

mutation

Question 4

define what horizontal gene transfer is:

Answer 4

genetic info is passed from one living cell go another cell of the same generation for example : plasmid transfer

Question 5

genetic info is passed from one living cell to another cell of the same generation

Answer 5

horizontal gene transfer

Question 6

True or false.
Horizontal gene transfer:

in either case:
Change is stable, and passed on to progeny

Answer 6

true

Question 7

Mutations :
what are the two steps:

Answer 7

1. Base substitution
2. Frameshift mutation

Question 8

define base substitution (point mutation)

Answer 8

a single nucleotide is replaced by another nucleotide

• when DNA replicates- results in a substituted base pair

when DNA is transcribed and translated can result in an incorrect amino acid in the protein - missense mutation

Question 9

when dna is transcribed and translated can result in an incorrect amino acid in the protein

Answer 9

missense mutation

Question 10

describe what missense mutation

Answer 10

when DNA is transcribed and translated can result in an incorrect amino acid in the protein

Question 11

frameshift mutation

Answer 11

insertion- one or two nucleotides added to the gene

deletion- one or two nucleotides removed from the gene

• changes the reading frame if the mRNA
  sequence of amino acids is changed “downstream” of mutation site

——- almost always results in a non functional protein

Question 12

how do mutations occur?
name the two fundamental steps

Answer 12

1.spontaneous mutation
2.induced mutation

Question 13

occur in absence of mutagens, due to occasional mistakes during DNA replication

Answer 13

spontaneous mutation

Question 14

define what spontaneous mutation means

Answer 14

occur in absence of mutagens, due to the occasional mistakes during DNA replication

Question 15

define what induced mutation is

Answer 15

occur when DNA damaging agents cause changes in DNA sequence - mutagens , for example : radiation, some chemicals

Question 16

regardless of origins, mutations can result in

Answer 16

1.no effect on the protein (remains functional)-silent mutation
2.a protein with a different aminoa cid sequence that may have an altered function - missense mutation
3.Premature stop codon- incomplete (truncated) protein, usually non functional- non sense mutation

Question 17

no effect on the protein (remains functional ) is

Answer 17

silent mutation

Question 18

define silent mutation

Answer 18

no effect on the protein (remains functional)

Question 19

A protein with different amino acid sequence that may have an altered function

Answer 19

missence mutation

Question 20

define what missense mutation is

Answer 20

a protein with a different amino acid sequence that may have an altered function

Question 21

Premature stop codon- incomplete (truncated) protein, usually nonfunctional

Answer 21

nonsense mutation

Question 22

define what nonsense mutation is

Answer 22

premature stop codon-incomplete (truncated) protein, usually non functional

Question 23

this is a self replicating, dsDNA molecules, and it contains non essential genes
for example : genes for toxin production

Answer 23

this is what we call plasmids

Question 24

define plasmids

Answer 24

self replicating, dsDNA molecules and it contains non essential genes
for example: genes for toxin production

Question 25

name the three kinds of plasmids

Answer 25

F plasmids
R plasmids
Vir plasmids

Question 26

what is a F plasmids?

Answer 26

another term is fertility factors, it carry genes to make F pilus (or sex pilus)
- it is also involved in conjugation (transfer of genetic information)

Question 27

what is r plasmids?

Answer 27

this is resistance factors , carry genes for antibiotic resistance

Question 28

what is vir plasmids?

Answer 28

virulence factors, carry genes for toxin production

Question 29

carry genes for antibiotic resistance

Answer 29

R plasmids

Question 30

involved in conjugation

Answer 30

F plasmids

Question 31

carry toxic gene production

Answer 31

vir plasmids

Question 32

what are the three basic methods of horizontal gene transfer?

Answer 32

transformation
transduction
conjugation

Question 33

define transformation

Answer 33

pieces of naked DNA are taken up by a bacterial cell example : from dead cells, or released plasmids

these pieces can be integrated into the chromosome recombination , can be passed to progeny and become a stable part of the genome

Question 34

define what transduction is

Answer 34

is a small fragments of DNA transferred between bacteria by bacteriophage

• viruses that infect bacteria

Phage attaches to bacterial cell wall-inject its DNA into the cell

Phage DNA is replicated inside the bacterial cell

Question 35

Define more characteristics about Transduction

Answer 35

Phage DNA also encodes enzymes that cut the bacterium’s DNA into fragments

As new phages are being assembled, some accidentally receive a piece of bacteria DNA instead of phage DNA
- transducing particle

the transducing particle can then carry bacterial genes to another cell

injection mechanism is still fully functional

But, bacterial DNA is injected into the cell

Question 36

True or false.
Transduction:
If the injected DNA recombines with the existing chromosome it becomes unstable genetic elements, however it will still be passed to progeny

Answer 36

false

Question 37

conjugation (bacterial mating) :

Answer 37

mediated by genes encoded on a F factor

Question 38

conjugation(bacterial mating): Transfers occurs when a:

Answer 38

Donor cell (F+)- forms an F pilus and uses it to attach to a recipient cell (F+)

Pilus retracts bringing the cell together

The donor cell replicates the F factor as a copy is passed to the recipient

The recipient becomes an F+ cell.