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Biology 260 > Unit 5 pt. 2 > Flashcards

Unit 5 pt. 2 Flashcards

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1
Q

Define horizontal gene transfer

A

The transfer of genetic information between organisms in the same generation

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2
Q

What are the 3 types of horizontal gene transfer that occur in bacteria?

A

Transformation

Transduction

Conjugation

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3
Q

Define Transformation

A

The process by which a cell takes up foreign DNA from its environment and incorporates it into its own

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4
Q

Define Transduction

A

The process by which bacterial DNA is transferred from one bacterium to another via a bacteriophage

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5
Q

Define Conjugation

A

DNA is transferred from one living bacterial cell to another with the sex pilis;

the cells must touch and after the process both cells have their own copy of the transferred DNA

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6
Q

What do all 3 of these mechanisms involve? (transformation, transduction, conjugation)

A

A donor cell that transfers a portion of its DNA to a recipient cell;

which may incorporate the new DNA into its own becoming a recombinant organism

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7
Q

A recombinant cell is a cell that receives DNA _____

A

from an outside source and incorporates it into its own

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8
Q

What is the hallmark of all horizontal gene transfers?

(basic definition)

A

Transfer of DNA between organisms of the same generation

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9
Q

What does it mean when a cell is competent?

A

can take up DNA from their surrounding environment and integrate it into their own chromosomes by recombination

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10
Q

Cells of a smooth strain produce a capsule that allows them to escape ______________

A

phagocytosis by the body’s defensive white blood cells

(unlike rough strain)

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11
Q

What can be used to kill the smooth strain?

A

Heat

S (heat-killed) cells when injected = mice live

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12
Q

R (live) + S (heat-killed) cells =

(both harmless)

A

death; s strain found in blood

because the harmless rough strain cells must have gained the genes to produce capsules like those of the virulent s strain cells

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13
Q

Mice that are injected with only the R strain of Streptococcus pneumoniae ___

A

stay healthy, because their immune systems can kill this strain easily

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14
Q

What characteristic of the S strain allows it to evade the immune system of the mice?

A

The cells have a capsule

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15
Q

What most likely explains the recovery of live S strain cells from a mouse injected with heat-killed S strain mixed with live R strain cells?

A

The R strain picked up the S strain DNA, enabling it to produce a capsule

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16
Q

Which finding is most surprising from Griffith’s experiments?

A

S strain cells are isolated from the blood of mice infected with heat-killed S strains and live R strains

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17
Q

Bacterial conjugation is often referred to as bacterial sex. Why is this term inaccurate?

A

Conjugation does not result in the formation of new offspring

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18
Q

What must occur for bacterial conjugation to take place?

A

The cells must come into contact with each other

19
Q

Which statement about conjugation is false?

a. E. coli is the model for bacterial conjugation.

b. Conjugation is a process of bacterial reproduction.

c. After conjugation, each cell involved has a copy of the shared DNA.

A

b. Conjugation is a process of bacterial reproduction.

20
Q

What is transferred during bacterial conjugation?

A

A bacterial plasmid

21
Q

What are cells containing an F factor called?

A

F+ cells;

they serve as DNA donors during conjugation

22
Q

What is an F factor?

A

Fertility factor or F plasmid

23
Q

What are conjugation pili or sex pili?

A

proteinaceous, rod like structures;

formed by (E. coli) cells containing an F factor

24
Q

What are cells lacking the F plasmid called?

A

F- cells;

they serve as DNA recipients during conjugation

25
Q

What happens at the start of conjugation?

A

A conjugation pilus extends from an F+ cell to an F- cell and pulls the cells together

26
Q

What happens in conjugation after the cells are pulled together by the pilus from the F+ cell?

A

The cells come together and stabilize, probably through fusion of their cell membranes then the transfer of DNA begins

27
Q

What is transferred between conjugation of F+ and F- cells?

A

A single stranded copy of the F factor is transferred from the F+ cell to the F- cell

Each cell synthesizes a complementary strand of the plasmid resulting in a complete copy of the plasmid in each cell

28
Q

What do both cells contain after conjugation of F+ and F- cells?

A

A copy of the F factor therefore both cells are now F+ cells and can go on to initiate conjugation with other F- cells

29
Q

What is the function of the conjugation pilus?

A

It pulls the F+ and F- cells together

30
Q

What is required by an F- cell to become an F+ cell?

A

F plasmid

31
Q

What is the key difference between donor cells and recipient cells?

A

An F plasmid (donor cell has)

32
Q

What cellular macromolecule is the fertility factor comprised of?

A

Nucleic acid

33
Q

At which point does a recipient cell become an F+ cell?

A

Formation of the complementary strand of the F factor

34
Q

How is F+ cell converted into a Hfr?

A(n) ______ integrates into the E. coli _____

A

An F factor integrates into the E. coli chromosome

35
Q

How are F+ and Hfr cells similar?

A

They both form conjugation pili which attach to F- cells

36
Q

Where does the DNA transfer begin with Hfr and F-?

A

In the middle of the F factor within the Hfr cell’s chromosome;

usually the chromosome breaks before it is completely transferred

37
Q

What is the result of the Hfr’s chromosome breaking before it is completely transferred?

A

The F- cell does not receive a full copy of the F factor;

because of this it remains F- however the DNA from the donor can recombine with the recipients chromosome giving the recipient new chromosomal genes

38
Q

How does an F+ cell differ from an Hfr cell?

A

Hfr strains have the F plasmid integrated into the chromosome

39
Q

Why does conjugation between an Hfr strain and an F- strain not result in two Hfr strains?

A

Conjugation is typically disrupted before the fertility factor can be transferred

40
Q

What are 3 characteristics of a F+ cell?

A
  1. Ability to synthesize sex pili
  2. Presence of a fertility factor
  3. Ability to mate with an F- cell
41
Q

What benefit does the F- strain receive from mating with an Hfr strain?

A

It acquires new, potentially beneficial genes from the Hfr strain

42
Q

A mutation that causes production of a defective pilus in a bacterium will prevent __________

A

Conjugation

43
Q

What was the scientific result of Frederick Griffith’s experiments with Streptococcus pneumoniae?

A

He showed that the DNA from strain S cells could transform strain R cells

Biology 260 (35 decks)

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