DNA – The Molecule of Life Lecture Notes

Vocabulary flashcards covering DNA structure, replication, protein synthesis, the Human Genome Project, and genetic disorders as outlined in the MYP Booklet 2025-2026.

Nucleic acids

Organic polymers made up of nucleotides (monomers) joined together, containing (carbon C), (Hydrogen H), (Oxygen O), (Nitrogen N), and (phosphorus P).

Nucleotide

The monomer of nucleic acids consisting of a 5-carbon pentose sugar, a phosphate group, and a nitrogen base.

DNA (Deoxyribonucleic acid)

A double-stranded, helical nucleic acid containing the sugar deoxyribose and the nitrogenous bases Adenine ($A$), Thymine ($T$), Cytosine ($C$), and Guanine ($G$).

RNA (Ribonucleic acid)

A single-stranded, non-helical nucleic acid containing the sugar ribose and the nitrogenous bases Adenine ($A$), Uracil ($U$), Cytosine ($C$), and Guanine ($G$).

Complementary base pairing

The specific rule where Thymine binds to Adenine using two hydrogen bonds, and Guanine binds to Cytosine using three hydrogen bonds.

Sugar-Phosphate Backbone

The structural framework of DNA formed by covalent bonds between the phosphate group of one nucleotide and the deoxyribose sugar of the next.

Antiparallel Strands

The arrangement of the two DNA strands running in opposite directions, one from $5'$ (five-prime) to $3'$ and the other from $3'$ to $5'$.

Erwin Chargaff

Biochemist who discovered in 1949 that the amount of adenine always equals the amount of thymine, and the amount of guanine equals the amount of cytosine.

Rosalind Franklin

Scientist who in 1950 improved X-ray diffraction patterns of DNA molecules, leading to the discovery of the helical shape.

James Watson and Francis Crick

Scientists who used Chargaff’s data and Franklin’s findings to create a 3-dimensional model of DNA, winning a Nobel prize in 1962.

Enzymes

Biological catalysts that speed up chemical reactions in cells without being consumed in the process.

Gene

Segments of DNA that carry information used to make proteins.

Genome

The entire collection of genes in an organism, population, or species.

Semi-conservative

The mechanism of DNA replication where each resulting DNA molecule consists of one original parent strand and one newly synthesized strand.

DNA Helicase

An enzyme that uses ATP energy to unwind the DNA double helix and break hydrogen bonds between complementary base pairs to form a replication fork.

DNA Polymerase

The enzyme responsible for assembling new DNA strands by adding nucleotides in the $5'$ to $3'$ direction and proofreading the sequence.

Okazaki fragments

Short DNA fragments synthesized discontinuously on the lagging strand against the direction of the replication fork.

Ligase

The enzyme that fills the spaces between Okazaki fragments by adding missing covalent bonds.

Transcription

The process occurring in the nucleus where RNA polymerase synthesizes a complementary mRNA copy using the antisense (template) strand of DNA.

Translation

The synthesis of a polypeptide in the ribosomes where mRNA sequence is read to determine the amino acid sequence.

Codon

A sequence of three DNA or mRNA bases that codes for a specific amino acid; there are $64$ different codons for $20$ amino acids.

Anticodon

A sequence of three nucleotides on a tRNA molecule that is complementary to a codon on an mRNA strand.

tRNA (Transfer RNA)

The molecule that acts as a bridge between the genetic code and amino acids, carrying the specific amino acid corresponding to the mRNA codon.

Human Genome Project (HGP)

An international effort completed in 2003 to sequence the $2.9$ billion DNA base pairs that make up the human genome.

Genomics

The study of entire genomes, specifically using technology to compare genes within and between species.

Genetic disorder

A disease caused by a change or mutation in an individual's DNA sequence.

Cystic fibrosis

A genetic disorder caused by inheriting a faulty CFTR gene missing three bases, leading to protein malfunction and lung blockages.

Huntington’s disease

A disorder caused by the repetition of the CAG (glutamine) genome section more than $35$ extra times, causing premature senility.

Hemophilia

A disorder caused by a faulty factor VIII protein, resulting in internal bleeding into joints or muscles.