DNA structure

What are the components of a nucleotide?

Phosphate group, sugar (deoxyribose in DNA, ribose in RNA), and nitrogenous base (A, T, U, G, C).

What type of bond links nucleotides in nucleic acids?

Phosphodiester bonds link nucleotides between the 5’ phosphate group of one and the 3’ hydroxyl group of another.

Which bases are considered purines?

Adenine (A) and Guanine (G) are purines.

What mnemonic helps to remember pyrimidine bases?

‘CUT the pie’ helps remember Cytosine, Uracil, and Thymine.

What is the pairing rule for complementary bases?

A pairs with T (or U in RNA), and G pairs with C.

How many hydrogen bonds are formed between A-T and G-C base pairs?

A-T (or A-U) has 2 hydrogen bonds; G-C has 3 hydrogen bonds.

What is the significance of G-C pairs in DNA?

G-C pairs are stronger and more stable, contributing to DNA stability and melting temperature.

What does the 5’ and 3’ designation refer to in nucleic acids?

5’ end has a phosphate group; 3’ end has a hydroxyl group.

What defines the antiparallel nature of DNA strands?

One DNA strand runs 5’ → 3’ while the other runs 3’ → 5’.

What are the major and minor grooves of DNA?

Major groove is larger and allows more access for protein binding; minor groove is smaller with limited protein interaction.

What are the key differences between DNA and RNA?

DNA contains deoxyribose, thymine, and is double-stranded; RNA contains ribose, uracil, and is single-stranded.

Why doesn’t DNA contain uracil?

Cytosine can deaminate to uracil, and having uracil in DNA would complicate the repair of deaminated cytosine.

What is the role of histones in DNA organization?

Histones are proteins that DNA wraps around to form nucleosomes, aiding in compaction.

What structure is formed by the DNA-histone complex?

A nucleosome is formed when DNA wraps around an octamer of histones.

What are the two types of chromatin?

Euchromatin (loosely packed and active) and heterochromatin (tightly packed and inactive).