Exam 2 Total Review

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Questions and Answers

What is the main function of photoreactivation in DNA repair?

Directly repairs UV induced damage (correct)

Corrects mismatched base pairs

Replaces missing nucleotide sequences

Removes damaged DNA segments

Which mechanism of horizontal gene transfer involves direct cell contact?

Transduction

Replication

Transformation

Conjugation (correct)

How do Hfr cells differ from F+ cells?

Hfr cells have the F plasmid integrated into their chromosomes (correct)

Hfr cells can only receive plasmids

F+ cells contain chromosomal DNA

F+ cells are integrated into the chromosome

What is the role of the operator in an operon?

Regulates the operon by binding repressors Signup and view all the answers

What distinguishes specialized transduction from generalized transduction?

It transfers specific genes adjacent to prophage integration sites Signup and view all the answers

What are restriction endonucleases primarily used for in genetics?

To cut DNA at specific sequences Signup and view all the answers

Which of the following methods increases the competency of cells for transformation?

Applying an electric field to create pores Signup and view all the answers

In blue-white screening, what does a white colony indicate?

Successful uptake of foreign DNA Signup and view all the answers

What is the primary purpose of nucleotide excision repair?

To remove segments of damaged DNA Signup and view all the answers

What is defined as the process of transferring genes from parent to offspring?

Vertical gene transfer Signup and view all the answers

What is generation time in microbial growth?

The time between successive binary fission of a cell Signup and view all the answers

During which phase of the bacterial growth curve do the symptoms of disease typically develop?

Log phase Signup and view all the answers

Which methods are commonly used to count the number of bacteria in a culture tube?

Direct microscope count and standard plate count Signup and view all the answers

Which classification of oxygen requirement includes organisms that cannot survive in the presence of oxygen?

Obligate anaerobes Signup and view all the answers

What does the streak plate method primarily aim to achieve?

Isolate pure bacterial colonies Signup and view all the answers

What does being VBNC indicate about an organism?

It is an organism that cannot be easily cultured in lab conditions Signup and view all the answers

Which group of bacteria is capable of undergoing fermentation?

Facultative anaerobes Signup and view all the answers

What does the catalase test determine about an organism's physiology?

Presence of enzymes that detoxify hydrogen peroxide Signup and view all the answers

Which of the following environmental conditions best supports the growth of psychrophiles?

0-15 degrees Celsius Signup and view all the answers

What is the optimal growth condition for mesophiles?

Temperature range of 20-45 degrees Celsius Signup and view all the answers

Which bacteria group primarily thrives at human body temperature and can be most pathogenic?

Mesophiles Signup and view all the answers

What mechanism allows Helicobacter pylori to survive in the acidic environment of the stomach?

Produces urease to convert urea to ammonia Signup and view all the answers

What type of medium supports the growth of fastidious organisms by providing extra nutrients?

Enriched media Signup and view all the answers

Which experiment demonstrated the transformation principle where non-virulent bacteria became virulent?

Frederick Griffith’s experiment Signup and view all the answers

How do eukaryotic transcription and prokaryotic transcription differ fundamentally?

Eukaryotic transcription occurs only in the nucleus and includes mRNA processing Signup and view all the answers

What is the role of the Shine-Dalgarno sequence in prokaryotic mRNA?

It facilitates translation initiation Signup and view all the answers

What is one of the key findings of Oswald Avery and his colleagues regarding genetic material?

DNA is the genetic material responsible for mutations Signup and view all the answers

What fundamental structure did Watson and Crick discover about DNA?

Double helix structure Signup and view all the answers

Which type of mutation results in the premature termination of protein synthesis?

Nonsense mutation Signup and view all the answers

How does polycistronic mRNA differ from monocistronic mRNA in bacterial cells?

Polycistronic mRNA encodes information for multiple genes Signup and view all the answers

Study Notes

Restriction Endonucleases

Enzymes that cut DNA at specific nucleotide sequences, called restriction sites.
Recognize palindromic sequences and make cuts, either blunt or sticky ends.
Used in genetic engineering to splice DNA fragments.

Competence

Ability of a cell to take up extracellular DNA.
Cells can become competent through:
- Natural competence: Certain conditions (e.g., Streptococcus)
- Chemical competence: Treating cells with calcium chloride to increase membrane permeability.
- Electroporation: Applying an electric field to create temporary pores in the cell membrane.
- Heat shock: Exposing cells to a sudden increase in temperature.

Molecular Cloning Steps

Isolating the DNA of interest using restriction enzymes.
Inserting the isolated DNA into a cloning vector (e.g., plasmid) using ligation.
Transforming the recombinant vector into a competent bacterial host cell.
Selecting the recombinant cells using antibiotic resistance or reporter genes.

Blue-White Screening

Technique to differentiate between bacterial colonies that contain recombinant plasmids and those that do not.
Bacteria with non-recombinant plasmids produce a blue color (due to β-galactosidase activity).
Bacteria with recombinant plasmids (foreign DNA insertion disrupts the lacZ gene) produce white colonies.

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Description

This quiz covers the fundamentals of molecular cloning, focusing on restriction endonucleases and cell competence. You'll learn about how these enzymes cut DNA and the steps involved in creating recombinant DNA. Test your knowledge on techniques used in genetic engineering and transformation methods.