To separate genomic DNA fragments by size, which of these laboratory methods is most useful?

A. Filtration

B. Spectrophotometry

C. Titration

D. Electrophoresis

Answer Explanation:

One of the most common techniques for separating DNA fragments by size is electrophoresis. Electrophoresis is a process that uses an electric field to move charged molecules through a porous gel matrix. The gel acts as a sieve, allowing smaller molecules to move faster and farther than larger ones. By applying a dye to the DNA samples and loading them into wells at one end of the gel, the DNA fragments can be visualized as bands after electrophoresis. The distance of each band from the well indicates the size of the corresponding DNA fragment.

Therefore, the Correct Answer is D.

Q #1: Which of the following substances protects the skin from ultraviolet radiation?

A. Melanin

B. Perspiration

C. Sebum

D. Keratin

Answer Explanation

One of the functions of the skin is to protect the body from harmful effects of ultraviolet (UV) radiation. UV rays can damage the DNA of skin cells and cause mutations that may lead to skin cancer. The skin has a natural defense mechanism against UV radiation, which is the production of a pigment called melanin. Melanin is synthesized by specialized cells called melanocytes, which are located in the basal layer of the epidermis. Melanin absorbs UV rays and prevents them from reaching the deeper layers of the skin.
Q #2: Which of the following is the structure through which blood exits the glomerulus?

A. Proximal tubule

B. Distal tubule

C. Afferent arteriole

D. Efferent arteriole

Answer Explanation

The glomerulus is a network of capillaries that filters blood and forms the primary urine. The blood enters the glomerulus through the afferent arteriole and leaves through the efferent arteriole. The efferent arteriole has a smaller diameter than the afferent arteriole, creating a high pressure in the glomerulus that facilitates filtration.
Q #3: Which of the following properties of water explains its solvent abilities for certain substances?

A. Polarity of water molecules

B. High specific heat

C. High surface tension

D. Kinetic energy of liquid water molecules

Answer Explanation

Water is a versatile solvent because it can dissolve many different kinds of substances. The reason for this is the polarity of water molecules, which means that they have a slight positive charge on one end and a slight negative charge on the other. This allows water molecules to attract and surround ions or polar molecules of other substances, forming hydration shells that separate them from each other.

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To separate genomic DNA fragments by size, which of these laboratory methods is most useful?

More Questions on TEAS 7 Science

Q #1: Which of the following substances protects the skin from ultraviolet radiation?

Answer Explanation

Q #2: Which of the following is the structure through which blood exits the glomerulus?

Answer Explanation

Q #3: Which of the following properties of water explains its solvent abilities for certain substances?

Answer Explanation

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