genetics test 4
where are exconjugants identified by their growth?
on a selective growth medium
How many donor genes may a new exconjugant aquire by homologous recombination?
one or more
What are exconjugants that contain a complete F' factor called?
partial diploids
How many chromosomes are usually in bacteria?
1
The passage of DNA into a recipient is accompanied by what?
degradation of one of the strands
What does the alignment of the donor and the recipient trigger?
excision of one strand of recipient DNA and REPLACEMENT WITH DONOR DNA... this forms a heteroduplex
What happens after contact is established by the conjugation pilus?
gene expression from the F factor produces a protein complex called a relaxosome
what are the 2 types of transduction?
general and specialized
what are small double stranded circular DNA molecules containing NON-ESSENTIAL genes?
plasmids
What is the name of the protein complex that the F factor produces?
relaxosome
Plasmids that can replicate independently of the bacterial chromosome so that the number of plasmids per cell can increase rapidly are called what?
high-copy-number plasmids
Transfer of one or more donor alleles into the recipient chromosome occurs by what?
homologous recombination
what are the parts of a bacteriophage?
icosahedral head, protein sheath, sometimes tail fibers
How will each Hfr strain used in interrupted mating experiments transfer genes?
in a specific order
T strand transfer across the pilus is accompanied by a specialized process called _______________________________
rolling circle replication
what did ledenberg and tatum hypothesize about bacterial genetic transfer?
that physical contact was needed
what is lysis?
the breakage of a donor cell and fragmentation of the DNA of the donor
what is the recipient cell called after conjugation?
the exconjugant
What does the recipient cells use as a template for replication?
the imported DNA
what does rolling circle replication use as a template for DNA replication?
the non-transferred DNA strand
What complex binds the coupling complex?
the nucleoprotein complex
what provides a recognition signal for the coupling complex?
the nucleoprotein complex at the 5' end of the T strand
what is the transformed cell called?
the transformant
What are experiments that test for gene transfer at timed intervals used for?
to determine the distances between genes
In an interrupted mating experiment, the purpose of plating cells on a selective medium is
to ensure that only recombinant genotypes are recovered
How is transformation used in the laboratory?
to introduce plasmids to recipient cells
what is a cell that has been attacked by a bacteriophage called?
transductant
What is the transfer of DNA from one bacterium to another by viral vector?
transduction
What is the uptake of DNA from the environment?
transformation
what does cotransformed mean?
transformed into the recipient on the same fragment of DNA
when does an episome occur?
when a plasmid integrates into the bacterial chromosome
When does Transformation occur?
when a recipient cell takes up a fragment of donor DNA from the surrounding growth medium
Can transformation be used to map genes?
yes
What can happen to the episome at each insertion sequence?
it can be oriented in either of two directions
Where is the location and orientation of F Factor?
it varies among Hfr strains
What will be the cotransformation frequency for two genes too far apart to be cotransformed? How many crossover events will it require?
it will be the product of the two transformation frequencies, 4
who identified bacterial DNA transfer and when?
ledenberg and tatum 1946
Mapping information for a single Hfr gene is ___________
limited
plasmids that are usuallly present in one or two per bacterial cell and cannot replicate independently are called what?
low-copy-number plasmids
What is transformation preceded by?
lysis
What are insertion sequence elements?
mobile segments of bacterial DNA that can transpose themselves to new locations
time-of-entry maps are constructed using what?
multiple Hfr strains
what kinds of plasmids are found in bacteria?
naturally occurring
Is the F fcator fully transferred during mating?
no
Where is the nucleoprotein complex located?
at the 5' end of the T strand
what are the 6 steps of the lytic cycle?
attachment, injection, replication, transcription/translation, packaging, lysis
what are the 4 steps of the lysogenic cycle
attachment/injection, integration, excision of prophage, resumption of lytic cycle
Why are partial diploids called partial diploids?
because they contain two copies of the bacterial chromosome genes found on the F' factor
how is genetic information transferred during conjugation?
by a conjugation pilus
How are the maps from each strain consolidated?
by identifying overlap regions from each strain
How can three genes' orders be determined?
by the cotransformation frequency
_____________________ will often end up on th esame fragment of transforming DNA and require only ______ crossover events. they will have a ___________________ frequency similar to the transformation frequency of a single gene
closely linked genes, 2, cotransformation
What is the transfer of replicated DNA from a donor to a recipient?
conjugation
Which kind of bacterial genetic transfer is closest to sexual reproduction
conjugation
How long is an F factor?
100 Kb
How many steps is transformation?
4
how many insertion sequence elements does a large component F factor consist of?
4
How many of the genes that control conjugation are encoded by the F factor?
40
What is time-of-entry-mapping?
Experiments that test for gene transfer at timed intervals
Which of the following transposition events is most likely to result in a loss of function mutation? A.Insertion of an IS element within the coding region of a gene B. Transposition of an IS element that contains a stop codon within the inverted repeat sequence C. Insertion near the promoter region of a gene
A.Insertion of an IS element within the coding
what kind of organism has nutritional requirements in addition to those of the normal organism and cannot make their own nutrients?
Auxotroph
You perform a cotransduction experiment with a leuA + met4 - tyr9 + proC - donor and a leuA - met4 + tyr9 - proC + recipient. You select for leuA + transductants by plating on minimal medium + methionine, tyrosine, and proline. The bacteriophage you use is capable of transducing more than 300 kilobases (kb) of DNA at a time. Based on the map, which of the following statements is(are) true? Check all that apply. A.The leuA + met4 - tyr9 - proC - genotype will be the most common transductant genotype. B.The leuA + met4 + tyr9 + proC + genotype will be the least common transductant genotype. C.The leuA + met4 - tyr9 + proC - genotype will be more common than the leuA + met4 - tyr9 + proC + genotype. D. The leuA + met4 - tyr9 - proC - genotype will be more common than the leuA + met4 + tyr9 - proC + genotype.
B.The leuA + met4 + tyr9 + proC + genotype will be the least common transductant genotype. C.The leuA + met4 - tyr9 + proC - genotype will be more common than the
Sort the items according to whether they may be found only in free virus particles, only in uninfected host cells, or in both viruses and host cells. Into Viruses only, Host Cell Only, or Both RNA DNA Capsid Protein Ribosome Envelope with glycoproteins Capsomere(core protein)
Both have DNA, RNA, and protein only host cells have ribosomes capsomeres, envelopes, and capsids are only in viruses.
All of the following are characteristics of insertion sequences elements except _______. A.they encode protein B. there can be more than one copy of an IS element in a bacterial genome C. a copy of the insertion sequence becomes integrated at a new location D. they are flanked by inverted repeats
C. a copy of the insertion sequence becomes integrated at a new location
The role of transposase activity in IS element transposition includes _______. A.truncating other proteins B.filling in single-stranded gaps after IS insertion C. regulating expression of the target sequence D. cutting DNA at the target sequence
D. cutting DNA at the target sequence
Which of the following statements about conjugation is true?
DNA is transferred from an F+ cell to an F− cell.
What did Cavalli-Sforza identify in 1953?
Donor strains that transferred bacterial genes rather than F factor genes at a high rate
What can take place at any Insertion sequence element on a bacterial chromosome?
F factor integration
What are donor cells carrying an F' factor called?
F' cells
An ______________________ contains a functional F factor derived from ________________________ of the F factor from an Hfr chromosome
F' donor bacterium, imperfect excision
what are donor cells that possess an F factor called?
F+ cells
What are recipients, those who lack an F factor, called?
F- cells
True or false? A bacterial strain that is pro+ thi+ leu− met− will grow on minimal media plus leucine and thiamine.
False
True or False. Partial diploidy is not retained as a characteristic of the exconjugant and their descendants.
False. It is retained
True or False. The formation of the Hfr chromosome is very common.
False. It occurs rarely.
true or false. Plasmids are ususally larger than bacterial chromosomes.
False. They are smaller
True or False. Transformation is not a naturally occurring mechanism.
False. it is naturally occurring.
what kind of plasmid contains genes that promote its own transfer from donors to recipients?
Fertility Plasmid
Mapping bacterial genes by conjugation is based on which of the following assumptions?
Genes are transferred from donor to recipient in a linear fashion.
What is the ability to act as a donor determined by?
Heredity and a fertility factor
WHat can we call F factor cells that have been integrated into bacterial chromosomes?
Hfr cells
The F factor integrates into the bacterial chromosome to form what?
Hfr chromosome
What did Cavalli-Sforza name his dicovery?
High frequency recombination (Hfr) strains
Instead of recircularizing, what happens to linear DNA in the recipient cell?
Homologous recombination occurs between the linear DNA and the circular chromosome of the recipient.
What are mobile segments of bacterial DNA that can transpose themselves to new locations
Insertion sequence elements
What is the cessation of conjugation by breaking the conjugation tube?
Interrupted mating
A newly discovered gene zig is tested for linkage to rag. A double auxotrophic bacterial strain with the genotype zig− rag− is transformed by a prototrophic bacterial strain (zig+ rag+ ). The individual transformation frequencies for the genes are 0.018% for zig and 0.012% for rag. In a screen of 108 cells, there are two zig+ rag+ cotransformants. Do the results indicate that zig and rag are linked?
NO
What is the difference between natural and induced transformation?
Natural transformation is when DNA fragments in the environment are taken up by the cell. The fragment can either be degraded or integrated with induced transformation, a plasmid is used, and stable transformation happens when the plasmid is taken up... there is no degradation
Can linear DNA in the recipient cell recircularize?
No
Conjugation with F' Strains produces what?
Partial diploids
what kind of plasmid carries antibiotic resistance genes that can be transferred to recipient cells
Resistance plasmid
True or False. Complete transfer of the bacterial chromosome is not accomplished
True
True or False. The ability to act as a donor could be restored after conjugation with another donor strain.
True
The ____________ unwinds and a protein called ___________ binds the free 5' end
T strand, relaxase
How is a merozygote formed?
The F factor and several adjacent genes are excised from the chromosome of an F+ cell and transferred to an F− strain.
Which of the following statements about mapping bacterial genes by conjugation is NOT true?
The closer a gene to the Hfr origin, the more likely it will be transferred to the recipient during conjugation.
THe order and time of each in exconjugants are related to what?
The distance from the origin of transfer (oriT)
Once F factor insertion has taken place what happens the the locatoin and direction of the F factor for that Hfr strain?
They remain constant
What will happen to genes closer to the oriT
They will transfer earlier and beincorporated more frequently into recipients
What is the transfer of genetic material from donor to recipient by bacteriophage
Transduction
where does rolling circle replication begin?
at oriT
who isolated a strain that formerly acted as a donor but lost its ability to do so? When did he do it?
William Hayes, 1953
What does a bacterial chromosome usually look like?
a covalently closed circular molecule of double stranded DNA
What kind of organism can generate all its own macromolecules from simple sugars and inorganic minerals?
a prototroph
the F' factor that results from imperfect excision contains what?
all its own DNA plus a segment of the bacterial chromosome
circular elements like the F factor can integrate into the bacterial chromosome to form what?
an episome
homologous recombination forms what?
an exconjugant chromosome
What is used as a tool to control growth of bacteria?
antibiotic sensitivity and resistance
Where does integration occur?
at insertion sequence elements
