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Lab 03B: HHMI Bacterial Identification
Virtual Lab Questions and Correct
Answers/ Latest Update / Already Graded
What is the piece of DNA used for identifying bacteria, and what does
this indentification rely on?
Ans: The region that codes for a small subunit of the ribosomal
RNA (16S RNA)
the identification relies on matching the sequence from your
sample against a database of all known 16S rDNA sequences
Describe the process of extracting bacterial DNA (sample preparation)
Ans: 1. dissolve the cell wall with digestive buffer
2. heat sample in a water bath 100°C to denature proteolytic
enzymes from digestive buffer
3. spin sample in centrifuge
4. transfer supernatant (the liquid) to PCR tube
Why do you heat the sample after adding the digestive buffer?
Ans: The buffer contains proteolytic enzymes that dissolve the
cell wall so DNA can be extracted. Once it does this, we must
denature the buffer to prevent the proteolytic enzymes from
interfering with the other enzymes used during PCR
All rights reserved © 2025/ 2026 |
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Where is the extracted bacterial DNA in the centrifuge tube?
Ans: The cellular debris is spun down in the centrifuge and
appears as a solid deposit (pellet). The DNA is contained in the
supernatant (the liquid) that is transferred to the PCR tube
how do you dissolve the cell wall to extract the bacterial DNA?
Ans: proteolytic enzymes in digestive buffer dissolve the cell
wall
what is PCR
Ans: polymerase chain reaction is a technique that allows many
copies of DNA to be made from a small original sample
describe what happens in PCR
Ans: In normal cells, the dsDNA is unzipped with an enzyme to
start the replication process. In PCR, ssDNA is made by heating
a chromosome fragment to 95°C. It is then cooled.
Why is the sample cooled after the 95°C water bath?
All rights reserved © 2025/ 2026 |
Lab 03B: HHMI Bacterial Identification
Virtual Lab Questions and Correct
Answers/ Latest Update / Already Graded
What is the piece of DNA used for identifying bacteria, and what does
this indentification rely on?
Ans: The region that codes for a small subunit of the ribosomal
RNA (16S RNA)
the identification relies on matching the sequence from your
sample against a database of all known 16S rDNA sequences
Describe the process of extracting bacterial DNA (sample preparation)
Ans: 1. dissolve the cell wall with digestive buffer
2. heat sample in a water bath 100°C to denature proteolytic
enzymes from digestive buffer
3. spin sample in centrifuge
4. transfer supernatant (the liquid) to PCR tube
Why do you heat the sample after adding the digestive buffer?
Ans: The buffer contains proteolytic enzymes that dissolve the
cell wall so DNA can be extracted. Once it does this, we must
denature the buffer to prevent the proteolytic enzymes from
interfering with the other enzymes used during PCR
All rights reserved © 2025/ 2026 |
, Page |2
Where is the extracted bacterial DNA in the centrifuge tube?
Ans: The cellular debris is spun down in the centrifuge and
appears as a solid deposit (pellet). The DNA is contained in the
supernatant (the liquid) that is transferred to the PCR tube
how do you dissolve the cell wall to extract the bacterial DNA?
Ans: proteolytic enzymes in digestive buffer dissolve the cell
wall
what is PCR
Ans: polymerase chain reaction is a technique that allows many
copies of DNA to be made from a small original sample
describe what happens in PCR
Ans: In normal cells, the dsDNA is unzipped with an enzyme to
start the replication process. In PCR, ssDNA is made by heating
a chromosome fragment to 95°C. It is then cooled.
Why is the sample cooled after the 95°C water bath?
All rights reserved © 2025/ 2026 |
