Chapter 7: Bacterial and Viral Genetic Systems Flashcards
What did the microorganism experiment with leu- and leu+ bacterial colonies tell us regarding supplemental mediums?
A colony that grows ONLY on the supplemented medium has a mutation in a gene that encodes the synthesis of an essential nutrient
Regarding medium consumption, which two types of bacteria exist?
- Prototrophic
- Auxotrophic
Define prototrophic bacteria
Wild type, can eat anything, can survive off minimum medium
Define auxotrophic bacteria
Cannot eat everything, needs a complete medium
Define minimum medium
A medium with scarely any nutrients, only required by prototrophic bacteria
Define complere medium
Contains all substances required by all bacteria, including auxotrophic bacteria
Are wild type bacteria signaled with a + or a -, what about mutant bacteria?
Wild type: +
Mutant type: -
Ex:
met+ = wild type
met - = mutant type
What does the symbol “s” mean regarding bacteria and antibiotics?
Sensitive to antibiotics
Ex: METs
What does the symbol “r” mean regarding bacteria and antibiotics?
Resistant to antibiotics
Ex: METr
Define plasmid
Extra-chromosomal small circles of DNA
Define conjugation
Direct transfer of DNA from one bacterium to another
What is the difference between transformation and transduction?
Transformation: Bacterium take up free DNA
Transduction: Bacterial viruses take DNA from one bacterium to another
Who all played a role in the discovery of conjugation? (3 people)
William Hayes: Discovered the “F” facotr
Lederberg and Tatum: confirmed recombination took place between 2 mutant strains
What is the F factor, and what does it mean?
F = fertility factor, which means one strain was always the donor while the other was always the recipient.
How are the two strains (donor and recipient) depicted? (X+ and X-)
F+ = donor
F- = recipient
What is an R plasmid?
Like an F plasmid it can rapidly replicate, but it also contains genes from many bacteria
T/F: R plasmids play a role in antibiotic resistance
True
What is the difference between a virus and a bacteriophage?
Virus: replicating structure (DNA/RNA) + protein cost
Bacteriophage: bacterial virus
There are 2 types of “phages” what are they?
- Virulent phage
- Temperate phage
Which reproduction cycle does virulent phage use?
Lytic cycle, always kills host cell
Which reproduction cycle do temperate phages use?
Lysogenic cycle, inactive prophase, phage DNA integrates into bacterial chromosome
T/F: Transduction usually occurs between bacteria of the same or closely related species
True
How does cotransuction rate and distance between genes relate? (cotransduction is just genes transferred together)
Higher cotransduction rate = lower distance between genes
Is influenza single or double-stranded?
Single
What is a retrovirus?
A virus that reverses transcription from RNA to DNA
A hypothetical bacterial colony grows well on minimal media plus raffinose. Select the genotype that most correctly represents this colony:
A) raf+
B) raf-
C) Raf^s
D) raf^R
Select the explanation of the genotype:
A) The colony is resistant to raffinose
B) The colony can utilize raffinose as a carbon source
C) The colony cannot utilize raffinose as a carbon source
D) The colony is sensitive to raffinose
A) raf+
and
B) The colony can utilize raffinose as a carbon source
Explanation:
- The question stated nothing regarding sensitivity r resistance, so raf^S and raf^R can be eliminated. If the colony DIDN’T grow on raffinose, it would be raf-, but because it did, it is raf+
- With the previous knowledge, resistance, and sensitivity are removed, and sine the colony can grow on raffinose it can utilize it as a carbon source.
What is the definition of an auxotroph?
A) an organism that grows well in the absence of a required metabolite
B) an organism that produces complex compounds in order to grow
C) an organism that uses organic carbon in order to grow
D) an organs that lacks to the ability to synthesize a required metabolite
D) an organs that lacks to the ability to synthesize a required metabolite
Which of the following are characteristics of F- bacterium? (2 correct answers)
- Bacteria with F factor integrated into the genome
- Contains a plasmid with only the F factor
- Contains a plasmid with the F factor and some genomic DNA
- Does not contain the F factor sequences
- Recipient of DNA during conjugation
- Does not contain the F factor sequences
- Recipient of DNA during conjugation
Which of the following is a characteristic of the F+ bacterium?
- Bacteria with F factor integrated into the genome
- Contains a plasmid with only the F factor
- Contains a plasmid with the F factor and some genomic DNA
- Does not contain the F factor sequences
- Recipient of DNA during conjugation
- Contains a plasmid with only the F factor
Which of the following is a characteristic of F’ (F-prime) bacterium?
- Bacteria with F factor integrated into the genome
- Contains a plasmid with only the F factor
- Contains a plasmid with the F factor and some genomic DNA
- Does not contain the F factor sequences
- Recipient of DNA during conjugation
- Contains a plasmid with the F factor and some genomic DNA
Which of the following is a characteristic of the Hfr bacterium?
- Bacteria with F factor integrated into the genome
- Contains a plasmid with only the F factor
- Contains a plasmid with the F factor and some genomic DNA
- Does not contain the F factor sequences
- Recipient of DNA during conjugation
- Bacteria with F factor integrated into the genome
Describe conjugation
DNA transferred from a donor to a recipient cell via direct connections
Describe transduction
DNA transfer mediated through the action of a bacterial virus
Describe transformation
Transfer of genetic material from the extra cellular environment
Organize the 4 steps of bacterial transformation into order of occurrence
Below are the steps organized alphabetically (not correctly)
1. An enzyme dissociated the DNA into single strands
2. A single-stranded fragment of DNA is imported into the cell
3. DNA binds to the DNA-binding complex
4. The DNA fragment recombines into a homologous region of the bacterial chromosome
- DNA binds to the DNA-binding complex
- An enzyme dissociated the DNA into single strands
- A single-stranded fragment of DNA is imported into the cell
- The DNA fragment recombines into a homologous region of the bacterial chromosome
Shorted version:
1. DNA binding
2. Enyme separation
3. DNA enters cell
4. DNA enters chromosome
How can the amount of frequencies in recombinants show the order of the recombinants?
The higher the frequencies, the closer to the reference point; the lower the frequency, the further.
Ex: In STR there are 100 recombinants of b+, 50 recombinants of a+ and 25 recombinants of d+. So the order is b+, a+, d+ based of recombination
Which of the following statements is true of plasmids?
a. They are composed of RNA
b. They normally exist outside bacterial cells
c. They possess only a single strand of DNA
d. They contain an origin of replication
d. They contain an origin of replication
Which process of DNA transfer in bacteria requires a virus?
a. Conjugation
b. Transduction
c. Transformation
d. All of the above
b. Transduction
Conjugation between and F+ and an F- cell usually results in
a. two F+ cells
b. Two F- cells
c. An F+ and an F- cell
d. an Hfr cell and an F+ cell
a. two F+ cells
A bacterial strain with the genotype his-leu-thr- is transformed with DNA from a strain that is his+leu+thr+. A few leu+thr+ cells and a few his+thr+ cells are found, but no his+leu+ cells are observed. Which genes are furthest apart?
his and leu
CRISPR-Cas systems are capable of remembering DNA from a specific pathogen by
a. Modifying the bacteria’s DNA by methylation
b. Acquiring plasmids with antibiotic resistance
c. Incorporating part of the pathogen DNA into the CRISPR array
d. Cleaving foreign DNA with restriction enzymes
c. Incorporating part of the pathogen DNA into the CRISPR array
In which bacteriophage life cycle does the phage DNA incorporate into the bacterial chromosome?
a. Lytic
b. Lysogenic
c. Both lytic and lysogenic
d. Neither lytic nor lysogenic
b. Lysogenic
In gene mapping using generalized transduction, bacterial genes that are contrasduced are
a. far apart on the bacterial chromosome
b. on different bacterial chromosomes
c. close together on the bacterial chromosome
d. on a plasmid
c. close together on the bacterial chromosome
What enzyme is used by a retrovirus to make a DNA copy of its genome?
Reverse transcriptase
