Chapter 6

Question 1

Compare size, packing of DNA, presence of introns, chromosomes, and mitochondria between eukaryotic and bacterial genomes

Answer 1

Eukaryotes: large genome, DNA associated w/ histone octamer coiled into chromatin, introns within genes, multiple chromosomes, mitochondria
Bacteria: small genome, DNA associated w/ histone proteins and supercoiled, no introns, typically one chromosome, no mitochondria

Question 2

T or F: plasmids contain essential genes that are necessary for life and plasmid DNA is always incorporated into the bacterial genome

Answer 2

False, plasmids contain nonessential genes that are usually not necessary for life - sometimes, plasmid DNA is incorporated into the bacterial genome.

Question 3

Fertility (F) plasmids VS Resistance (R) plasmids

Answer 3

F plasmids: contain genes that assist w/ transfer of that plasmid to another host bacterial cell
R plasmids: contain genes that confer antibiotic resistance

Question 4

What are the three types of lateral gene transfer?

Answer 4

1) Conjugation
2) Transformation
3) Transduction

Question 5

Conjugation is the…

Answer 5

transfer of replicated DNA from a donor cell to a recipient cell

Question 6

Transformation is the…

Answer 6

uptake of DNA from the environment

Question 7

Transduction is the..

Answer 7

transfer of DNA from one bacterium to another by a viral vector (bacteriophage)
bacteriophage attaches to donor cell, phage DNA injection causes chromosome fragmentation, phages package donor DNA and attach to a recipient cell

Question 8

Lateral gene transfer

Answer 8

the transfer of genetic material between individual bacteria or archaea and other organisms (same or different species)

Question 9

Describe conjugation between two bacterial cells, one with an F plasmid and one without

Answer 9

The donor cell with the F plasmid is (F+) & the recipient cell without an F plasmid is (F-). The donor cell creates a pilus, connecting the two bacterial cells. A relaxosome complex binds to the F plasmid at the origin of transfer (oriT) and the single strand enters the recipient cell. Both donor and recipient cells are now (F+)

https://www.youtube.com/watch?v=7Q9Eg1GV6WI

Question 10

How does an (F+) bacterial cell convert into an Hfr strain?

Answer 10

Within an (F+) cell, recombination can occur between the bacterial chromosome and F plasmid at an IS element. This incorporates the F plasmid into the bacterial genome, producing a “high frequency recombination” (Hfr) strain.

Question 11

Explain Hfr conjugation from an Hfr cell to an (F-) cell

Answer 11

With Hfr conjugation, donor bacterial chromosomal genes can be transferred to the recipient, where homologous recombination occurs between this transferred linear DNA and the circular chromosome of the recipient, generating recombinants

Question 12

What is the purpose of the recipient cell (F-) in Hfr conjugation having an R plasmid?

Answer 12

???

Question 13

Describe the concept of interrupted mating and time of entry mapping for bacterial genomes.

Answer 13

An Hfr cell that contains specific genes undergoes Hfr conjugation with an (F-) cell that has the opposite genes. By observing how long it would take for each gene to transfer over to the recipient cell, they could map the entire bacterial genome by distance. Multiple Hfr strains can be used to map all the genes since a single Hfr strain is limited and would break apart before the whole donor genome is transferred.

Question 14

T or F: in mapping bacterial genomes, F+ conjugation could be used too.

Answer 14

False, only Hfr conjugation works since F+ conjugation does not transfer donor bacterial chromosomes over to the recipient cell.

Question 15

Describe F’ conjugation from a F’ cell to an F- cell

Answer 15

An F’ cell is produced when the F factor is separated from an Hfr strain but the F factor now contains genes from the bacterial chromosome. When crossed w/ an (F-) cell, the recipient cell now has two copies of a gene

Question 16

Question 1: was the exconjugant converted to donor state?
Question 2: was the donor bacterial genes transferred to exconjugant?
For (F+ x F-), (Hfr x F-), and (F’ x F-), answer these questions

Answer 16

(F+ x F-): yes, no
(Hfr x F-): no, yes
(F’ x F-): yes, yes

Question 17

A cell capable of being transformed is said to be _______________

Answer 17

competent

Question 18

Describe the Lytic Cycle

Answer 18

phage attaches to host cell, injects phage DNA, phage DNA replicates, transcribing and translating, progeny phages are produced and then released via lysis

Question 19

Describe the Lysogenic Cycle

Answer 19

phage attaches to host cell, injects phage DNA, which integrates into host chromosome (prophage), eventually excised from the host chromosome, and the lytic cycle resumes

Question 20

T or F: during the lysogenic cycle, it is true that the prophage may stay attached to the host bacterial chromosome for several generations before being excised

Answer 20

True

Question 21

When bacteriophages infect bacteria, a spot with dead bacteria forms called a ________.

Answer 21

plaque

Question 22

Fine-structure mapping using lambda phages revealed combination could occur within genes. Bacteria could be ______________ by phage strains with different mutations that prevented normal plaque development. However, rare recombination could occur within these genes that created a functional ___________, meaning ___________________ could form.

Answer 22

coinfected, wild-type allele, normal plaques