DNA and RNA focused

What are the three components of a nucleotide?

Nitrogenous base, pentose sugar, and phosphate group

Which nitrogenous bases are purines?

Adenine and guanine

Which nitrogenous bases are pyrimidines?

Cytosine, thymine (DNA), and uracil (RNA)

What is the difference between a nucleoside and a nucleotide?

A nucleoside has only a base and sugar; a nucleotide also includes a phosphate group

What sugar is found in RNA?

Ribose

What sugar is found in DNA?

Deoxyribose

Which base is unique to RNA?

Uracil

Which base is unique to DNA?

Thymine

Which DNA base pairs with cytosine?

Guanine (G≡C, 3 hydrogen bonds)

Which DNA base pairs with adenine?

Thymine (A=T, 2 hydrogen bonds)

Which RNA base pairs with adenine?

Uracil

How many hydrogen bonds are in a G≡C base pair?

Three

How many hydrogen bonds are in an A=T or A=U base pair?

Two

What is the most common form of DNA in cells?

B-form DNA

What is a distinguishing feature of B-form DNA?

Right-handed helix, ~10.5 bp per turn, wide major groove

What conditions favor A-form DNA?

Low hydration or RNA helices and DNA-RNA hybrids

What type of DNA has a left-handed helix?

Z-DNA

What is the major groove in DNA?

The wider groove that allows protein access for base sequence recognition

Why is RNA less stable than DNA?

RNA has a 2′-OH group that makes it prone to hydrolysis

What is a hairpin loop in RNA?

A structure where RNA folds back on itself forming a stem of base pairs and a loop

What type of pairing occurs in RNA hairpins?

A=U and G≡C, sometimes G=U wobble pairing

What is the difference in strand structure between DNA and RNA?

DNA is usually double-stranded; RNA is usually single-stranded

Why does RNA form complex 3D structures?

Due to intramolecular base pairing and secondary structures like loops and bulges

What is the functional relevance of the major groove in DNA?

It's the primary site where proteins bind and recognize specific DNA sequences

How are phosphodiester bonds involved in nucleic acids?

They link nucleotides together between the 3′ OH and 5′ phosphate

Which form of DNA has tilted bases and a narrow major groove?

A-form DNA

What are pseudoknots in RNA?

Complex tertiary structures where bases in a loop pair with complementary bases outside the loop