Unit 1 Study Guide: The Chemistry of Heredity

Nucleic acids

Essential macromolecules that store, transmit, and express hereditary information.

Nucleotide

The monomer of nucleic acids, consisting of a five-carbon sugar, a phosphate group, and a nitrogenous base.

Phosphate Group

A component of nucleotides attached to the 5' carbon of the sugar, contributing to DNA's acidic character.

Nitrogenous base

Variable part of a nucleotide that carries the genetic code.

Purines

Nitrogenous bases with a double-ring structure; includes Adenine and Guanine.

Pyrimidines

Nitrogenous bases with a single-ring structure; includes Cytosine, Thymine, and Uracil.

Dehydration synthesis

Process by which nucleotides connect to form a polynucleotide chain.

Phosphodiester bond

The bond between the phosphate group of one nucleotide and the sugar of the next.

Sugar-Phosphate Backbone

The structural framework of nucleic acids formed by phosphodiester bonds.

5' End

The end of a nucleic acid strand that terminates with a phosphate group.

3' End

The end of a nucleic acid strand that terminates with a hydroxyl (-OH) group.

Double helix

The structure of DNA, consisting of two strands twisted around each other.

Antiparallel strands

Refers to the orientation of DNA strands running in opposite directions.

Deoxyribose

The pentose sugar in DNA, lacking an oxygen atom at the 2' carbon.

Base pairing rules

Rules dictating how nitrogenous bases pair; A pairs with T, and G pairs with C.

A-T pair

A pair linked by 2 hydrogen bonds.

G-C pair

A pair linked by 3 hydrogen bonds.

RNA

Ribonucleic acid that translates genetic code from DNA into proteins.

Ribose sugar

The sugar in RNA that has a hydroxyl (-OH) group at the 2' carbon.

Uracil

A nitrogenous base in RNA that pairs with Adenine and replaces Thymine.

Single-stranded

The typical structure of RNA, existing as a single polynucleotide strand.

DNA stability

DNA is highly stable for long-term storage, in contrast to the less stable RNA.

Confusing directionality

A common mistake where students think DNA strands run the same way instead of anti-parallel.

Bond type confusion

Mistaking hydrogen bonds for covalent bonds in the sugar-phosphate backbone.

Identifying the ends

Mistaking bases for determining the direction when the phosphate and hydroxyl groups should be considered.

Uracil vs Thymine

Mistaking Thymine as RNA and Uracil as DNA; T indicates DNA while U indicates RNA.