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Genetics > Chapter 7 > Flashcards

Chapter 7 Flashcards

1
Q

What are the 9 advantages of using bacteria and viruses for genetic studies?

A
  1. Reproduction is rapid
  2. Many progeny reproduced
  3. The haploid genome allows all mutations to be expressed directly
  4. Asexual reproduction simplifies the isolation of genetically pure strains
  5. Growth in lab is easy and requires little space
  6. Genomes are small
  7. Techniques are available for isolating and manipulating bacterial genes
  8. They have medical importance
  9. They can be genetically engineered to produce substances of commercial value
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2
Q

What are the characteristics of prokaryotes?

A

Unicellular, no nucleus, no membrane bound organelle, diverse shapes and sizes, binary fission, haploid, single circular dsDNA chromosome, most of the genome encode protein.

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3
Q

What do organisms need to live?

A
  • An energy source (like carbohydrates)
  • May need organic growth factors (like an amino acid)
  • Lack of toxins or ability to breakdown toxins (like antibiotics)
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4
Q

What are catabolic genes?

A

Provide information to synthesize enzymes needed to break down molecules for energy. Break down carbohydrates, like gal and lac.
Can be gal+, gal-, lac+, lac-
‘+’ means they can break it down
‘-‘means they can’t

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5
Q

What are anabolic genes?

A

Provide information to synthesize enzymes needed to make molecules. Makes amino acids like his, trp, leu, thr
Each can have either a ‘+’ or a ‘-‘
‘+’ means they can synthesize it
‘-‘ means they can’t

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6
Q

What are antibiotic resistant genes?

A

Provide information to synthesize enzymes needed to make molecules. Resist antibiotics.
examples are amp, tet
can be ampr, amps
tetr, tets
‘r’ means they are resistant
‘s’ means they aren’t

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7
Q

What is a prototrophic?

A

Wild type (ex. leu+), can live on minimum media

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8
Q

What is an auxotrophic?

A

Mutant type (ex. leu-), need complete media: contain all substances required by auxotrophic bacteria.

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9
Q

Does E. coli (his-) on a plate with media that does NOT contain the amino acid histidine grow bacteria? What about E. coli (his+)?

A

E. coli (his-) does not grow bacteria.
E. coli (his+) does grow bacteria.

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10
Q

Does E. coli (lac-) on a plate with media that contains only lactose as an energy source grow bacteria? What about with E. coli (lac+)?

A

E. coli (lac-) does not grow bacteria.
E. coli (lac+) does grow bacteria.

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11
Q

Does E. coli (ampr) on a plate with media that contains ampicillin grow bacteria? What about E. coli (amps)?

A

E. coli (ampr) does grow bacteria.
E. coli (amps) does not grow bacteria.

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12
Q

Why is replica plating used?

A

It’s useful for screening and selecting for mutants. A colony that grows only on the supplemented medium has a mutation in a gene that encodes the synthesis of an essential nutrient.

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13
Q

What are plasmids?

A

Small, circular DNA distinct from the chromosome. Carry genes not essential to function, could have important roles. (promote conjugation, produce compounds that kill other bacteria, antibiotic resistant, metabolism, genetic engineering)

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14
Q

What is the origin?

A

The special starting point for DNA replication.

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15
Q

What did the Lederberg and Tatum experiment prove?

A

Bacteria can exchange large pieces of genetic information

Bacteria’s genes can also change in a way similar to that of sexual reproduction seen in more complex organisms

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16
Q

What do the U-tube experiments show?

A

They provide a way to ascertain if transfers are due to conjugation, transformation, or transduction.
It’s conjugation if the auxotrophs do not change phenotype.
If they do change, it could be either transformation or transduction. You can use DNase to degrade free DNA to figure it out (viruses protect DNA from degrading in the presence of DNase).

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17
Q

What are the 3 types of gene transfer in bacteria?

A
  1. Conjugation- direct transfer of DNA from on bacterium to another.
  2. Transformation- bacterium takes up free DNA.
  3. Transduction- bacterial viruses take DNA from one bacterium to another.
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18
Q

How do the 3 transfers of bacteria differ from genetic exchange that occurs in sexual reproduction?

A
  1. DNA exchange and reproduction are not coupled in bacteria.
  2. Donated genetic material not recombined into the host DNA is usually degraded.
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19
Q

In conjugation, what are F+, F-, Hfr, and F’ (prime) cells?

A

F+ cells: donor cells contain F factor

F- cells: recipient cells lacking F factor

Hfr cells: donor cells with F factor integrated into the donor bacterial chromosome- process can reverse, so Hfr cell becomes F+ or F’.

F’ cells: Contains F plasmid carrying some bacterial genes.

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20
Q

What is an F factor?

A

A piece of DNA that is either autonomous or integrated into the bacterial DNA.

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21
Q

How is distance between genes measured during conjugation?

A

Measured by the time required for DNA transfer from Hfr cells to F- cells.

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22
Q

Cotransformation between two genes is more likely if they are:

A

Close to one another.

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23
Q

Which explanation is one of the reasons for the ability of the influenza virus to evolve rapidly?

A

The virus may undergo antigenic shift when multiple strains infect the same organism.

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24
Q

A cell that carries a F factor integrated into the bacterial chromosome is best known as a/an:

A

Hfr cell

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25
Q

You place a bacterial culture (labeled culture A) that is his+ ampr on one side of a u-tube apparatus and a bacterial culture (labeled culture B) that is his-amps on the other side. Both sides of the U-tube apparatus contain DNase. Later, you grow some of culture B in media that contains ampicillin and is deficient in histidine. There is now some growth of the bacteria on the plates. Which example of gene transfer in bacteria is the best explanation of what happened?

A

Transduction

26
Q

Bacteria have to make physical contact- Conjugation, transformation, or transduction?

A

Conjugation

27
Q

F+ can transfer to F- in this process- Conjugation, transformation, or transduction?

A

Conjugation

28
Q

Requires phage to act as an intermediary- Conjugation, transformation, or transduction?

A

Transduction

29
Q

This process requires bacterial cell to be competent- Conjugation, transformation, or transduction?

A

Transformation

30
Q

In a U-tube experiment, the presence of DNase prevents which process from happening?- Conjugation, transformation, or transduction?

A

Transformation

31
Q

Involves the uptake of free DNA from the environment- Conjugation, transformation, or transduction?

A

Transformation

32
Q

Experimentally, studying this process may require growing bacteria as lawns on plates and looking for the presence of plaques- Conjugation, transformation, or transduction?

A

Transduction

33
Q

This process was used for generating a map of the E. coli chromosome based on time- Conjugation, transformation, or transduction?

A

Conjugation

34
Q

What happens on R plasmids?

A

Antibiotic resistance comes from the actions of genes located on the R plasmids that can be transferred naturally. The transfer of R plasmids is not
restricted to bacteria of the same or even related species

35
Q

Why are R plasmids important?

A

They cause antibiotic resistance, and they have evolved in the past 60 years, as the use of antibiotics is being more widespread.

36
Q

What is transformation in the bacteria exchange genes go through?

A

A bacterium takes up DNA from the medium, recombination takes place between introduced genes and the bacterial chromosome.

37
Q

What are competent cells? (In transformation)

A

Cells take up DNA

38
Q

What are transformants? (In transformation)

A

Cells that receive genetic material

39
Q

What is cotransformed? (In transformation)

A

Cells that are transformed by two or more genes.

40
Q

What does transformation look like?

A
41
Q

Are viruses alive?

A

No

42
Q

What are viruses?

A

Simple replicating systems amenable to genetic analysis. They are the replicating structure (DNA/RNA) + protein coat. Made of proteins and nucleic acid.

43
Q

What are virulent phages?

A

Reproduce through the lytic cycle, and always kill the host cells.

44
Q

What are temperate phages?

A

inactive prophage— phage DNA integrates into bacterial chromosome (lysogeny)

45
Q

What are the lytic and lysogenic cycles?

A

In the lytic cycle, viruses quickly take over the host cell, make many copies, break the cell, and infect other cells. In the lysogenic cycle, viruses sneak into the host’s DNA, stay hidden, and wait. Later, they become active, make copies, and infect other cells.

46
Q

What is prophage in a lysogenic cycle?

A

The phage DNA integrates into the bacterial chromosome and becomes a prophage (step 3). The prophage is replicated as part of the bacterial chromosome- and can continue through many cell divisions. The prophage may separate from the chromosome and the cell will enter the lytic cycle.

47
Q

What is lysis in a lytic cycle?

A

Bacterial cells are broken open (lysed) and destroyed after immediate replication of the virion. As soon as the cell is destroyed, the phage progeny cam find new hosts to infect.

48
Q

What is the difference between plaques and colonies in microbiology?

A

In colonies, we directly observe the accumulation of large numbers of bacteria, each pile being a colony. In plaques, we directly observe the absence of bacteria against a background of dense bacterial growth, each zone of destruction being a phage plaque (hole) in the lawn of bacteria

49
Q

How do you grow bacteriophages?

A

You must grow bacteria to grow phages. Cultures are grown by infecting bacterial cells. They must infect a host cell in order to reproduce- lytic or lysogenic replication strategies.

50
Q

What is transduction?

A

Bacterial viruses (bacteriophages) carry DNA from one bacterium to another. Transduction usually occurs between bacteria of the same or closely related species.

51
Q

Why is transduction a rare event? (three reasons)

A
  1. The phage degrades the bacterial chromosome.
  2. The process of packaging DNA into the phage particle not be specific for phage DNA.
  3. The bacterial genes transferred by the virus recombine with the chromosome in the recipient cell.
52
Q

What does transduction look like?

A
53
Q

What is cotransduction?

A

The process by which two genetic markers are simultaneously packaged within a bacteriophage for transfer to a new host bacterium. Genes close to one another are more likely to be cotransduced, so the rate of cotransduction is inversely proportional to the distances between genes.

54
Q

How do you map phage genes?

A

Homologous recombination between phage chromosomes.

55
Q

What is a retrovirus and reverse transcriptase? (both a part of HIV/AIDS)

A

RNA viruses that can integrate into the
host genome.
Reverse transcriptase is the synthesis of DNA from an RNA template.

56
Q

What is the type of cells HIV infects?

A

T-helper cells. HIV is deadly if untreated because of the cell type it infects.

57
Q

What is influenza A?

A

Most cases are influenza A- divided into subtypes based on expression of hemagglutinin (HA) and neuraminidase (NA). Can infect more than just humans too. Rapid changes occur through genetic mutation or more major genetic exchanges between viruses.

58
Q

antigenic drift vs. antigenic shift

A

Antigenic drift occurs when viruses undergo gradual mutations in their genetic makeup. Antigenic shift occurs when viruses undergo a sudden change in their genetic makeup, creating a new virus strain

59
Q

What is SARS-CoV-2?

A

The cause of COVID-19, a large +ssRNA genome, a relatively large genome, envelope.
E protein, S protein, M protein (spikes, membrane, envelope, and nucleocapsid proteins)
Family: Coronaviridae

60
Q

What are the 3 types of bacterial transfer?

A

Genetics (23 decks)

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