Question

__________is a technique to determine the order of nucleotides in a fragment of DNA. a. PCR b. DNA sequencing c. Electrophoresis d. Nucleic acid hybridization

Short answer

b. DNA sequencing

Step-by-step solution

Identify the Question

We need to determine which technique is used to determine the order of nucleotides in a DNA fragment. The options provided are PCR, DNA sequencing, Electrophoresis, and Nucleic acid hybridization.

Option Analysis: PCR

PCR, or Polymerase Chain Reaction, is a technique used to amplify DNA, meaning it creates many copies of a specific DNA segment but does not determine the order of nucleotides.

Option Analysis: DNA Sequencing

DNA sequencing is specifically a process used to determine the precise order of nucleotides in a DNA molecule. This directly matches the definition provided in the question.

Option Analysis: Electrophoresis

Electrophoresis is a method used to separate DNA fragments by size but does not provide information about the order of nucleotides in a DNA fragment.

Option Analysis: Nucleic Acid Hybridization

Nucleic acid hybridization is a process used to determine if certain nucleic acid sequences are present in a sample by creating hybrid structures, but it does not determine nucleotide order.

Answer Selection

Based on the analysis of all options, DNA sequencing is identified as the correct technique used to determine the order of nucleotides in a DNA fragment.

Key concepts

Nucleotide Order

In the vast world of genetics, understanding the sequence or order of nucleotides is crucial. Nucleotides are the basic building blocks of DNA and RNA, consisting of a phosphate group, a sugar, and a nitrogenous base. The sequence of these nucleotides encodes the genetic information necessary for life's functions. The order of nucleotides in a DNA molecule dictates the genetic instructions used in the growth, development, functioning, and reproduction of all known living organisms and many viruses. Determining this order accurately is vital for many applications, such as identifying genetic disorders, developing drugs, and exploring the intricacies of evolution. To determine the order, scientists use DNA sequencing techniques, which analyze the specific arrangement of nucleotides. DNA sequencing can pinpoint the precise order, offering insights that are essential for biotechnology, medical diagnosis, and forensic science. In summary:

• Nucleotides include: a sugar, a phosphate group, and a base.
• The order of these nucleotides forms the genetic code.
• This order is key to understanding genetic information and its implications.

Electrophoresis

Electrophoresis is a laboratory technique primarily used to separate molecules based on size and charge. It plays an important role in the analysis of DNA, RNA, and proteins. In DNA analysis, electrophoresis involves applying an electric field to a gel, with DNA fragments migrating through the gel matrix. The electric current causes smaller DNA fragments to move faster and farther than larger ones, effectively sorting them by size. This technique, however, doesn't provide the sequence of nucleotides; it only separates DNA fragments. Electrophoresis is crucial for visualizing DNA fragments after processes like PCR and for checking the quality and size of DNA before proceeding to sequencing. Some key points about electrophoresis include:

• Uses an electric field to move DNA fragments through a gel.
• Sorts DNA fragments by size but not by order.
• Commonly used in conjunction with other techniques like PCR.

Polymerase Chain Reaction (PCR)

Polymerase Chain Reaction, better known as PCR, is a revolutionary method used widely in molecular biology. This technique allows scientists to amplify a specific DNA segment, making millions of copies from a small initial sample. PCR is essential in many areas, from cloning DNA for recombination to diagnosing genetic diseases and detecting pathogens. The fundamental steps of PCR involve:

• Denaturation: Heating the DNA so that the strands separate.
• Annealing: Cooling the reaction so that primers can attach to the single strands of DNA.
• Extension: DNA polymerase extends the primers to form a new DNA strand.

Though PCR dramatically amplifies DNA, it's important to note that it doesn't determine the nucleotide order. It's frequently used to produce enough DNA for detailed studies or sequencing, which can then determine the sequence.

Nucleic Acid Hybridization

Nucleic acid hybridization is a technique used to identify relationships between DNA or RNA sequences. This method involves joining two complementary strands of nucleic acids to form a hybrid molecule. It serves as a way to detect the presence of a specific sequence among a mixture of DNA or RNA. By hybridization, scientists can determine whether particular genetic sequences are present in a specimen. This method is particularly useful in research for understanding gene expression and for diagnostic tests, such as detecting viral infections or genetic diseases. For nucleic acid hybridization:

• It identifies the presence of specific sequences.
• Works by recognizing complementary bases to form hybrids.
• Does not determine nucleotide order but confirms sequence presence.

In conclusion, while it's a powerful tool for locating sequences, hybridization is complementary to sequencing techniques.