Question 1

Which of the following best explains why RNA can be hydrolyzed by alkali, but DNA cannot?

Accepted Answer

RNA has a 2'-hydroxyl group on the ribose sugar, which can participate in base-catalyzed hydrolysis, while DNA lacks this group.

Question 2

Which base pairing is responsible for the increased stability of DNA compared to RNA?

Accepted Answer

Guanine pairs with cytosine via three hydrogen bonds.

Question 3

A mutation causes the replacement of a cytosine with a thymine in a DNA strand. What is the most likely effect on the DNA structure?

Accepted Answer

It will decrease the stability of the DNA double helix due to loss of a triple hydrogen bond.

Question 4

Which of the following is NOT a function of DNA polymerase during DNA replication?

Accepted Answer

Joining Okazaki fragments together.

Question 5

During PCR (Polymerase Chain Reaction), which step is responsible for the separation of DNA strands?

Accepted Answer

Denaturation

Question 6

Which of the following statements about restriction enzymes is TRUE?

Accepted Answer

They cut DNA at specific recognition sequences.

Question 7

A researcher uses gel electrophoresis to analyze DNA fragments. What property of DNA allows separation in this technique?

Accepted Answer

DNA's negative charge due to phosphate groups

Question 8

Which of the following is a correct representation of the structure of ATP?

Accepted Answer

$$\mathrm{Adenine} - \mathrm{Ribose} - \mathrm{Three\ phosphate\ groups}$$

Question 9

Which of the following enzymes is used to join DNA fragments during molecular cloning?

Accepted Answer

DNA ligase

Question 10

Fatty acids are classified based on the presence and number of double bonds. Which of the following is a polyunsaturated fatty acid?

Accepted Answer

Linoleic acid ($$\mathrm{C$$_{18}$$H_{32}O$$_{2}}$)

Question 11

Which of the following is a function of phospholipids in biological membranes?

Accepted Answer

Forming the bilayer structure that provides membrane fluidity and barrier function

Question 12

A patient presents with symptoms of night blindness. Which vitamin deficiency is most likely responsible?

Accepted Answer

Vitamin A

Question 13

Which of the following is a consequence of vitamin C deficiency?

Accepted Answer

Scurvy

Question 14

Which of the following best describes the amphipathic nature of phospholipids?

Accepted Answer

They have both hydrophilic heads and hydrophobic tails.

Question 15

Which of the following is the correct formula for the calculation of the melting temperature ($$T_m) of $$DNA?

Accepted Answer

$$T_m = 2$$^{\circ}$$\mathrm{C} 	imes (\mathrm{A} + \mathrm{T}) + 4$$^{\circ}$$\mathrm{C} 	imes (\mathrm{G} + \mathrm{C})$$

Question 16

Which of the following is a key difference between prokaryotic and eukaryotic gene expression?

Accepted Answer

Eukaryotes process mRNA by splicing out introns before translation.

Question 17

Which vitamin is essential for the synthesis of clotting factors in the liver?

Accepted Answer

Vitamin K

Question 18

A patient is diagnosed with a deficiency in vitamin B12. Which of the following symptoms is most likely to be observed?

Accepted Answer

Megaloblastic anemia

Question 19

Which of the following best describes the role of restriction enzymes in recombinant DNA technology?

Accepted Answer

They cut DNA at specific sequences to allow insertion of foreign DNA.

Question 20

Which of the following is a correct statement about the structure of nucleotides in DNA?

Accepted Answer

Each nucleotide consists of a nitrogenous base, a deoxyribose sugar, and a phosphate group.

Biochemistry Exam 3 Study Guide: Nucleic Acids, Protein Techniques, and Lipids

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