Module Two a

Question 1

what is vertical gene inheritance?

Answer 1

asexual reproduction via cell division

Question 2

what are the three types of horizontal gene transfer?

Answer 2

• conjugation
• transduction
• transformation

Question 3

what is horizontal gene transfer?

Answer 3

organism acquires genes directly from another cell and incorporates them into its genome

• responsible for the spread of fitness-enhancing traits, including antibiotic resistance
• provides an awesome mechanism for ongoing adaptive evolution

Question 4

what is conjugation?

Answer 4

DNA transfer through cell-to-cell contact mediated by a mobile genetic element such as a plasmid

Question 5

what is conjugation mediated by?

Answer 5

a mobile genetic element like a plasmid

Question 6

what is transduction?

Answer 6

DNA transfer mediated by a bacteriophage

Question 7

what is transformation?

Answer 7

uptake of naked DNA into a competent recipient cell

Question 8

what is the direction of transfer?

Answer 8

unidirectional, from donor to recipient

Question 9

how much of the genome is transferred?

Answer 9

only part of the genome

Question 10

what form is the DNA in when it is transferred?

Answer 10

in a linear form that cannot replicate autonomously

Question 11

how are genes stably inherited?

Answer 11

they must be recombined into the recipient chromosome

Question 12

what was the basis of Lederberg’s experiment?

Answer 12

• represented the first use of conditional mutants to select against the parental type
• the mutants were double mutants so reversion artifacts were avoided
• the prototrophic recovery technique had enormous sensitivity

Question 13

what was the Davis U-tube experiment?

Answer 13

Two strains are added into a U-tube, seperated by a fine filter
It was mixed for several hours and then the solutions from each side of the U-tube were plated

Question 14

what were the results of the Davis U-tube experiment?

Answer 14

no recombinants

Question 15

what did the Davis U-tube experiment show?

Answer 15

that physical contact is required for genetic recombination

Question 16

how does an F factor transfer?

Answer 16

F factor can transfer from F+ cell to F- cell at high frequency by rolling circle mechanism

F- becomes F+ while F+ remains F+

F+ does not mate with F+ (surface exclusion)

Question 17

what is the donor F plasmid?

Answer 17

Donor F+ (male)

Question 18

what is the recipient F plasmid?

Answer 18

Recipient F- (female)

Question 19

how are Hfr strains formed?

Answer 19

by homologous recombination between identical copies of an insertion sequence or transposon present on F and on the chromosome

Question 20

what are the structural features of the F plasmid?

Answer 20

~100.00 Kb
hok/sok
pif
oriT

Question 21

what is the disrupted mating experiment?

Answer 21

added plasmids to a blended and blended them at different intervals

Question 22

what are the conclusions from the interrupted mating experiment?

Answer 22

• each donor allele first appears in recipient at a specific time after mating begins
• donor alleles appear in a specific sequence
• the maximal yield of cells containing a specific donor marker is lower for the donor markers that enter later
• Hfr chromosome is transferred in a linear fashion, beginning a specific origin. The further from O, the later a gene will be transferred and the more likely the transfer process will be interrupted before the gene is transferred.

Question 23

how many crossovers is required to incorporate transferred DNA?

Answer 23

An even number of crossovers

Question 24

What is the purpose of High Resolution Mapping by recombination Frequency?

Answer 24

to determine the distance between markers (interrupted mating will determine the order of markers)

Question 25

what is the problem with mapping by recombination frequency?

Answer 25

there are more recombination with markers closer to the origin

Question 26

what is the basis of mapping by recombination frequency?

Answer 26

Select for the latest marker to enter and screen for earlier markers

Question 27

what does the frequency of recombinant classes show?

Answer 27

the order of the genes on the chromosome and the distance between each pair of genes

Question 28

where does conjugation occur?

Answer 28

Diverse bacteria
F and yeast
Plants, fungi, yeats, agrobacterium, and human cells

Question 29

what are the features of the E.coli chromosome?

Answer 29

• 4,638,858 base pairs
• 4200 genes
• 48 transposable elements
• genes of related function often clustered into operons

Question 30

what is generalized Transduction?

Answer 30

• bacteriophage acts as a passive carrier of bacterial DNA which is injected into the recipient cell and incorporated by recombination
• any bacterial gene can be transduced at a low frequency
• the amount of DNA that can be transferred is limited by the size of the phage head

Question 31

what is transformation?

Answer 31

uptake of naked DNA into a competent recipient cell

Question 32

what are the two strains of pneumococci?

Answer 32

smooth (S) and rough (R)

Question 33

what experiment was done about DNA transformation?

Answer 33

the Avery-Macleod-McCarty Experiment

Question 34

what is competence?

Answer 34

specialised cell state

Question 35

what is the mechanism for DNA incorporation in transformation?

Answer 35

by homologous recombination, replacing host DNA