Nucleic Acid Structures and Functions

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Biochemistry › Nucleic Acid Structures and Functions

Questions 1 - 10
1

Which of the following statements about B DNA are incorrect?

B DNA has a wide and deep major groove and a narrow and shallow minor groove

B DNA is the most commonly found double helical structure

B DNA is right handed with 10 base pairs per turn

B DNA has a diameter of

All of these are correct

Explanation

B DNA has a wide and deep major groove and a narrow and deep minor groove. All other statements regarding B DNA are true.

2

The backbone of a strand of DNA is comprised of which of these?

Sugars and phosphates

Sugars and nucleotides

Nucleotides and phosphates

Sugars only

Nucleotides only

Explanation

The backbone of DNA is made up of alternating phosphate groups and sugar groups, linked together via phosphodiester bonds. The nitrogenous bases jut off of the backbone and form bonds with nitrogenous bases on other strands of DNA to become double stranded. A nucleotide consists of a sugar, nitrogenous base, and one or more phosphate groups.

3

Which of the following nitrogenous bases is a purine?

Adenine

Cytosine

Thymine

Uracil

Explanation

In DNA and RNA, there are two types of nitrogenous bases: pyrimidines and purines. A pyrimidine contains one carbon-nitrogen ring with two nitrogen atoms. A purine consists of a pyrimidine fused with an imidazole ring. Adenine and guanine are purines. Cytosine, thymine, and uracil are pyrimidines.

4

Which of the following statements about B DNA are incorrect?

B DNA has a wide and deep major groove and a narrow and shallow minor groove

B DNA is the most commonly found double helical structure

B DNA is right handed with 10 base pairs per turn

B DNA has a diameter of

All of these are correct

Explanation

B DNA has a wide and deep major groove and a narrow and deep minor groove. All other statements regarding B DNA are true.

5

What is the role of xanthine oxidase?

I. The enzyme xanthine oxidase converts hypoxanthine to xanthine and, also, xanthine to uric acid.

II. Xanthine oxidase is involved in purine (nucleotides like adenine, guanine) degradation.

III. In diseases where there is a high production of purines, the enzyme's products (uric acid) can cause gout.

IV. Gout medication is designed to target xanthine oxidase.

I, II, III, and IV

I and IV

I, II, and III

II, III, and IV

I and II

Explanation

Xanthine oxidase is an enzyme important in purine catabolism. Nucleotides from DNA degradation are metabolized to uric acid by xanthine oxidase.In diseases with high levels of nucleotide production, uric acid levels are also high and produce symptoms of gout (uric acid is deposited abnormally in tissues). Gout is treated with inhibitors of xanthine oxidase such as allopurinol, reducing the levels of uric acid and the symptoms of gout.

6

The backbone of a strand of DNA is comprised of which of these?

Sugars and phosphates

Sugars and nucleotides

Nucleotides and phosphates

Sugars only

Nucleotides only

Explanation

The backbone of DNA is made up of alternating phosphate groups and sugar groups, linked together via phosphodiester bonds. The nitrogenous bases jut off of the backbone and form bonds with nitrogenous bases on other strands of DNA to become double stranded. A nucleotide consists of a sugar, nitrogenous base, and one or more phosphate groups.

7

What is the role of xanthine oxidase?

I. The enzyme xanthine oxidase converts hypoxanthine to xanthine and, also, xanthine to uric acid.

II. Xanthine oxidase is involved in purine (nucleotides like adenine, guanine) degradation.

III. In diseases where there is a high production of purines, the enzyme's products (uric acid) can cause gout.

IV. Gout medication is designed to target xanthine oxidase.

I, II, III, and IV

I and IV

I, II, and III

II, III, and IV

I and II

Explanation

Xanthine oxidase is an enzyme important in purine catabolism. Nucleotides from DNA degradation are metabolized to uric acid by xanthine oxidase.In diseases with high levels of nucleotide production, uric acid levels are also high and produce symptoms of gout (uric acid is deposited abnormally in tissues). Gout is treated with inhibitors of xanthine oxidase such as allopurinol, reducing the levels of uric acid and the symptoms of gout.

8

What is the role of xanthine oxidase?

I. The enzyme xanthine oxidase converts hypoxanthine to xanthine and, also, xanthine to uric acid.

II. Xanthine oxidase is involved in purine (nucleotides like adenine, guanine) degradation.

III. In diseases where there is a high production of purines, the enzyme's products (uric acid) can cause gout.

IV. Gout medication is designed to target xanthine oxidase.

I, II, III, and IV

I and IV

I, II, and III

II, III, and IV

I and II

Explanation

Xanthine oxidase is an enzyme important in purine catabolism. Nucleotides from DNA degradation are metabolized to uric acid by xanthine oxidase.In diseases with high levels of nucleotide production, uric acid levels are also high and produce symptoms of gout (uric acid is deposited abnormally in tissues). Gout is treated with inhibitors of xanthine oxidase such as allopurinol, reducing the levels of uric acid and the symptoms of gout.

9

Which of the following nitrogenous bases is a purine?

Adenine

Cytosine

Thymine

Uracil

Explanation

In DNA and RNA, there are two types of nitrogenous bases: pyrimidines and purines. A pyrimidine contains one carbon-nitrogen ring with two nitrogen atoms. A purine consists of a pyrimidine fused with an imidazole ring. Adenine and guanine are purines. Cytosine, thymine, and uracil are pyrimidines.

10

Which of the following statements about B DNA are incorrect?

B DNA has a wide and deep major groove and a narrow and shallow minor groove

B DNA is the most commonly found double helical structure

B DNA is right handed with 10 base pairs per turn

B DNA has a diameter of

All of these are correct

Explanation

B DNA has a wide and deep major groove and a narrow and deep minor groove. All other statements regarding B DNA are true.

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