DNA Review

Question 1

can you describe the structure of a nucleotide?

Answer 1

1. Nitrogenous base: Can be a purine (adenine or guanine) or a pyrimidine (cytosine, thymine in DNA, or uracil in RNA).
2. Pentose sugar: A five-carbon sugar that determines the type of nucleotide.
   - Ribose: Found in RNA.
   - Deoxyribose: Found in DNA (lacks an oxygen atom at the 2’ carbon compared to ribose).
3. Phosphate group(s): One to three phosphate groups are attached to the 5’ carbon of the sugar.

Question 2

how do ribonucleotides and deoxyribonucleotides differ?

Answer 2

Ribonucleotides:
-Contain ribose as the sugar.
-Have a hydroxyl group (-OH) on the 2’ carbon of the sugar.
-Use uracil instead of thymine.
Deoxyribonucleotides:
- Contain deoxyribose as the sugar.
-Lack the hydroxyl group on the 2’ carbon (only a hydrogen is present).
-Use thymine instead of uracil.

Question 3

can you describe the structure of a polynucleotide?

Answer 3

A polynucleotide is a chain of nucleotides linked together through phosphodiester bonds.
- Phosphodiester bond: A covalent bond between the 3’ hydroxyl group of one nucleotide’s sugar and the 5’ phosphate group of the next nucleotide.
- These bonds form a sugar-phosphate backbone: a repeating structure of alternating sugar and phosphate groups.

Question 4

can you describe how a polynucleotide has a 5’ to 3’ orientation?

Answer 4

Polynucleotides have an inherent directionality:
- 5’ end: Has a free phosphate group attached to the 5’ carbon of the sugar.
- 3’ end: Has a free hydroxyl group (-OH) attached to the 3’ carbon of the sugar.

This orientation is critical for biological processes like DNA replication and transcription, which proceed in the 5’ to 3’ direction.

Question 5

Can you describe complementary base pairing in nucleic acids?

Answer 5

• Adenine (A) pairs with Thymine (T) via two hydrogen bonds.
• Guanine (G) pairs with Cytosine (C) via three hydrogen bonds.
  RNA Base Pairs:
• Adenine (A) pairs with Uracil (U) via two hydrogen bonds (replacing thymine found in DNA).
• Guanine (G) pairs with Cytosine (C) via three hydrogen bonds.

Question 6

what is the type of bond involved in complentary base pairing?

Question 7

how many bonds are between each base pair?