1. What is the main purpose of cell lysis during DNA isolation?
A.
To break open the cell and release its contents
B.
To join two DNA fragments
C.
To cut DNA at specific sites
D.
To introduce DNA into a host cell
Correct Answer:
To break open the cell and release its contents
Explanation:
Cell lysis breaks the cell membrane or cell wall, allowing the cellular contents, including DNA, to be released.
2. Which type of substance is commonly used to disrupt the cell membrane during cell lysis?
A.
Detergent
B.
Restriction enzyme
C.
DNA ligase
D.
Antibiotic marker
Correct Answer:
Detergent
Explanation:
Detergents disrupt the lipid membrane of cells and help release the cellular contents during lysis.
3. Which physical method can help break open cells during DNA isolation?
A.
Grinding the tissue
B.
Adding DNA ligase
C.
Using a cloning vector
D.
Cutting DNA with a restriction enzyme
Correct Answer:
Grinding the tissue
Explanation:
Grinding mechanically breaks cells and tissues, helping release their contents for DNA isolation.
4. What happens to a cell membrane when a suitable detergent is added during lysis?
A.
It is disrupted
B.
It becomes a DNA molecule
C.
It forms a plasmid
D.
It joins DNA fragments
Correct Answer:
It is disrupted
Explanation:
Detergents disturb the lipid structure of the cell membrane, causing it to break apart and release cell contents.
5. Which enzyme is commonly used to help lyse bacterial cells by breaking down their cell wall?
A.
Lysozyme
B.
DNA ligase
C.
RNA polymerase
D.
Restriction endonuclease
Correct Answer:
Lysozyme
Explanation:
Lysozyme breaks down the peptidoglycan layer of bacterial cell walls, assisting in cell lysis.
6. Cell lysis is usually performed at which stage of DNA isolation?
A.
At the beginning
B.
After DNA ligation
C.
After transformation of the host cell
D.
After selection of recombinant cells
Correct Answer:
At the beginning
Explanation:
Cells must first be opened so that their DNA can be released for subsequent isolation steps.
7. What is released when cells are lysed during DNA isolation?
A.
Cellular contents including DNA
B.
Only restriction enzymes
C.
Only plasmid vectors
D.
Only DNA ligase
Correct Answer:
Cellular contents including DNA
Explanation:
Lysis opens the cells and releases their contents, including genomic DNA and other cellular components.
8. Which treatment can help lyse plant cells by weakening their rigid cell walls?
A.
Mechanical grinding
B.
DNA ligation
C.
Transformation
D.
Restriction mapping
Correct Answer:
Mechanical grinding
Explanation:
Plant tissues can be mechanically ground to break their cells and assist in releasing DNA.
9. Why is gentle handling often used after cell lysis during DNA isolation?
A.
To reduce unwanted physical damage to the released DNA
B.
To make DNA enter a host cell
C.
To join DNA fragments together
D.
To create a restriction site
Correct Answer:
To reduce unwanted physical damage to the released DNA
Explanation:
Once DNA is released by lysis, gentle handling helps prevent unnecessary shearing or breakage of the DNA molecules.
10. Which structure must be disrupted to release DNA from a bacterial cell?
A.
Cell membrane and, where present, cell wall
B.
DNA restriction site only
C.
Plasmid origin of replication only
D.
Ribosome only
Correct Answer:
Cell membrane and, where present, cell wall
Explanation:
Bacterial lysis requires disruption of the cell membrane and often the cell wall so that the cellular contents and DNA can escape.
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