Problem 7 - Biology Today and Tomorrow with Physiology

Question

Fragments of DNA can be separated by electrophoresis according to ______. a. sequence b. length c. species

Step-by-Step Solution

Answer

DNA fragments are separated by electrophoresis according to their length.

Step 1: Understand the Question

We need to determine what characteristic of DNA fragments allows them to be separated by electrophoresis from the choices given: sequence, length, or species.

Step 1: Analyze DNA Fragment Separation

In electrophoresis, DNA fragments are separated based on a physical characteristic as they move through a gel in an electric field.

Step 2: Evaluate Separation Factor

The main factor that affects the movement of DNA fragments in an electric field is their length or size. Shorter fragments move faster and farther than longer ones, due to less resistance from the gel matrix.

Step 3: Apply Concept to Choices

Considering electrophoresis uses size as the separation factor, compare this understanding with the given options: - Sequence: Less relevant to physical separation - Length: Directly related to movement through gel - Species: Not relevant to separation mechanism

Step 4: Conclude Decision

Based on the analysis, length is the characteristic that allows DNA fragments to be separated by electrophoresis.

Key Concepts

DNA fragment length

DNA fragment length is a vital characteristic that determines how DNA fragments move during electrophoresis. In a gel electrophoresis setup, DNA fragments are sorted based on their size when an electric current is applied. This movement depends on the length of the fragment because the gel matrix acts like a sieve, where smaller fragments navigate more easily through the pores, traveling further across the gel.
Longer DNA fragments face more resistance and thus, travel a shorter distance compared to their shorter counterparts. This principle of sorting by length allows researchers to separate DNA fragments and understand genetic information efficiently. This method is particularly useful in various biological and genetic studies, such as analyzing genetic mutations or conducting paternity tests.

gel electrophoresis

Gel electrophoresis is a powerful technique used extensively in molecular biology to separate macromolecules like DNA, RNA, and proteins. A gel, usually made from agarose or polyacrylamide, serves as the medium through which these molecules travel when an electric field is applied. The gel acts as a physical barrier that impedes the movement of larger molecules more than smaller ones.
During the process:

• The DNA samples are placed in wells at one end of the gel.
• An electric current is applied, causing the molecules to move towards the positive electrode, since DNA is negatively charged.
• The varying speeds at which these DNA fragments travel cause them to separate based on size.

Gel electrophoresis is crucial for visualizing the sizes of DNA fragments, which can then be compared to known standards for analysis. This allows scientists to draw conclusions about the genetic makeup of a sample.

separation techniques in biology

Separation techniques in biology are fundamental processes used to isolate and analyze different biological components, such as cells, proteins, and nucleic acids. These techniques are crucial in research and diagnostic laboratories because they enable the study of specific molecules or cellular components in detail.
Some of the most common separation techniques include:

• Centrifugation: uses centrifugal force to separate particles based on density.
• Chromatography: separates components based on their movement through a medium.
• Electrophoresis: utilizes an electric field to separate charged particles, such as DNA or proteins, based on size and charge.

These techniques allow scientists to purify compounds, assess the purity of samples, and support the identification of molecular structures. Electrophoresis, specifically, is invaluable for genetic studies and the analysis of biomolecules.