Question 1

Which of the following best explains why a mortar and pestle are used in the wheat germ DNA isolation protocol but not in the cheek cell protocol?

Accepted Answer

Plant cells have a rigid cell wall that must be mechanically broken, while human cheek cells lack a cell wall.

Question 2

During the DNA isolation procedure, what is the main function of EDTA?

Accepted Answer

To chelate divalent cations such as $$\mathrm{Mg$$^{2+}$$}$$ and $$\mathrm{Ca$$^{2+}$$}$$, thereby inhibiting DNase activity.

Question 3

What is the primary reason cold ethanol is used during the DNA precipitation step?

Accepted Answer

DNA is insoluble in cold ethanol, causing it to precipitate out of solution.

Question 4

Which of the following best describes the composition of a DNA nucleotide?

Accepted Answer

A phosphate group, deoxyribose sugar, and a nitrogenous base.

Question 5

In the DNA isolation protocol, what is the main purpose of adding Sodium Dodecyl Sulfate (SDS)?

Accepted Answer

To denature proteins, disrupt the nuclear envelope, and release DNA from histones.

Question 6

After the first centrifugation of the wheat germ homogenate, what is found in the pellet at the bottom of the tube?

Accepted Answer

Nuclei containing DNA.

Question 7

Why is it important to balance centrifuge tubes before centrifugation?

Accepted Answer

To prevent damage to the centrifuge and ensure even separation of components.

Question 8

Which of the following steps is critical for preventing DNA degradation during isolation?

Accepted Answer

Adding EDTA to inhibit DNase enzymes.

Question 9

What is the role of sodium chloride (NaCl) in the DNA isolation protocol?

Accepted Answer

To precipitate nuclear proteins, allowing DNA to remain in solution.

Question 10

If, after completing the DNA isolation protocol, no DNA is visible at the ethanol interface, which of the following is NOT a likely reason?

Accepted Answer

The DNA was completely dissolved by the ethanol.

Question 11

Which of the following best describes the structure of eukaryotic chromatin prior to DNA isolation?

Accepted Answer

DNA wrapped around histone proteins, forming nucleosomes.

Question 12

In the context of the DNA isolation protocol, what is a 'homogenate'?

Accepted Answer

A mixture containing cytoplasmic components, organelles, and plasma membrane fragments.

Question 13

Which of the following is a key difference between prokaryotic and eukaryotic DNA as described in the study materials?

Accepted Answer

Eukaryotic DNA is linear and found in a nucleus, while prokaryotic DNA is circular and found in a nucleoid region.

Question 14

A student forgets to add SDS during the DNA isolation protocol. Which of the following outcomes is most likely?

Accepted Answer

DNA remains tightly bound to histones and nuclear membranes, reducing yield.

Question 15

Which of the following best explains why proteinase K is added during the cheek cell DNA isolation protocol?

Accepted Answer

To break down proteins and facilitate the release of DNA.

Question 16

If a student uses warm ethanol instead of cold ethanol during DNA precipitation, what is the most likely result?

Accepted Answer

Less DNA will precipitate because DNA is more soluble in warm ethanol.

Question 17

Which of the following steps in the wheat germ DNA isolation protocol is specifically designed to separate nuclei from other cellular components?

Accepted Answer

Low-speed centrifugation.

Question 18

A student observes no visible DNA after following the protocol. Which of the following is a plausible explanation based on the materials?

Accepted Answer

DNase was not inhibited, leading to DNA degradation.

Question 19

Which of the following best describes the role of histones in eukaryotic cells?

Accepted Answer

They package and organize DNA into nucleosomes.

Question 20

During the DNA isolation protocol, why is it important to avoid disturbing the interface between the ethanol and DNA solution after adding ethanol?

Accepted Answer

Disturbing the interface can prevent DNA from aggregating and becoming visible.

Bio 100 LAB 3 Chapter 3 UPDATED

Study Guide - Practice Questions