DNA Sequencing Methods

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Which of the following best describes the primary purpose of DNA sequencing?

To package DNA into a more compact form for cellular storage.
To determine the precise order of nucleotide bases in a DNA molecule. (correct)
To amplify specific DNA regions for cloning.
To measure the overall size and mass of a DNA strand.

What is the fundamental principle behind the Maxam-Gilbert method of DNA sequencing?

Hybridization of fluorescent probes to specific DNA sequences.
Real-time monitoring of nucleotide incorporation during DNA synthesis.
Enzymatic extension of DNA using modified nucleotides.
Chemical modification and cleavage of DNA at specific bases. (correct)

In the Maxam-Gilbert method, what is the purpose of treating the DNA fragment with alkaline phosphatase?

To add a phosphate group to the 5' end of the DNA.
To protect the DNA from degradation during subsequent steps.
To remove the 5' phosphate group, preparing it for labeling. (correct)
To denature the DNA into single strands.

Which reagent is used in the Maxam-Gilbert method to specifically modify guanine residues in DNA?

Dimethyl sulfate (A) Signup and view all the answers

Which of the following is a major disadvantage of the Maxam-Gilbert method compared to the Sanger method?

It involves more intermediate purification steps and is not easily automated. (D) Signup and view all the answers

What key component is used in the Sanger sequencing method to terminate DNA chain elongation?

Dideoxyribonucleotide triphosphates (ddNTPs) (B) Signup and view all the answers

Why is the absence of a 3'-OH group crucial for the function of ddNTPs in the Sanger method?

It allows the ddNTP to be incorporated into the DNA strand but prevents further extension. (B) Signup and view all the answers

Which of the following applications is NOT directly supported by DNA sequencing technologies?

Determining the secondary structure of proteins. (D) Signup and view all the answers

In Sanger sequencing, what is the role of ddNTPs (dideoxynucleotides)?

They terminate DNA strand elongation at specific nucleotide positions. (C) Signup and view all the answers

Why are four separate reaction tubes used in Sanger sequencing?

To allow for the incorporation of a different ddNTP (ddATP, ddCTP, ddGTP, or ddTTP) in each reaction. (A) Signup and view all the answers

Which of the following components is NOT required for a Sanger sequencing reaction?

Reverse transcriptase (C) Signup and view all the answers

What is the purpose of gel electrophoresis in Sanger sequencing?

To separate DNA fragments based on their size, allowing for sequence determination. (D) Signup and view all the answers

What key advantage does the Sanger method offer over the Maxam-Gilbert method?

The Sanger method uses enzymatic reactions, whereas the Maxam-Gilbert method relies on chemicals. (B) Signup and view all the answers

Which of the following is a direct result of the incorporation of a ddNTP into a growing DNA strand during Sanger sequencing?

Further nucleotide addition to that strand is halted. (B) Signup and view all the answers

Why is it important to include a small amount of ddNTPs in each Sanger sequencing reaction?

To allow for controlled termination at every possible nucleotide position while still allowing for some full-length strands to be synthesized. (B) Signup and view all the answers

How are the DNA fragments generated during Sanger sequencing typically detected after gel electrophoresis?

By using autoradiography to detect radiolabeled primers or dNTPs. (A) Signup and view all the answers

DNA Sequencing

Determining the precise order of nucleotide bases (A, T, C, G) within a DNA molecule.

Purpose of DNA Sequencing

Understanding the genetic instructions, detecting mutations, typing microorganisms and identifying genetic variations, helping to understand disease and inheritance.