Unit 3 – Molecular Genetics

DNA

A double helix composed of two antiparallel strands of nucleotides.

Nucleotide Components

Each nucleotide consists of a phosphate group, deoxyribose sugar, and a nitrogenous base (A, T, C, G).

DNA

A double helix composed of two antiparallel strands of nucleotides.

Nucleotide Components

Each nucleotide consists of a phosphate group, deoxyribose sugar, and a nitrogenous base (A, T, C, G).

Base Pairing

A-T and C-G pairs are held by hydrogen bonds in DNA.

Leading Strand

The strand synthesized continuously toward the replication fork during DNA replication.

Lagging Strand

The strand synthesized in fragments away from the replication fork, requiring multiple primers.

Central Dogma

The flow of genetic information from DNA to RNA to protein.

Transcription

The process of converting DNA into mRNA.

Translation

The process of converting mRNA into a protein.

Triplet Hypothesis

The theory that three nucleotides (a codon) in mRNA specify one amino acid.

Homeostasis

The process of maintaining a stable internal environment within an organism.

Negative Feedback

A mechanism that reverses a change to return to normal conditions, as seen in body temperature regulation.

Positive Feedback

A process that amplifies a change, exemplified by contractions during childbirth.

Reflex Arc

The neural pathway involved in reflex actions, consisting of stimulus, receptor, sensory neuron, interneuron, motor neuron, and effector.

Action Potential

The change in membrane potential that occurs when a neuron sends a signal, involving resting potential, depolarization, repolarization, and refractory period.

Hypothalamus

Brain structure that regulates hunger, thirst, body temperature, and hormones.

Medulla Oblongata

Part of the brain that controls autonomic functions such as heart rate and breathing.

Epinephrine

A hormone released by the adrenal gland that prepares the body for stress; also functions as a neurotransmitter.

Thyroid Function Errors

Conditions stemming from thyroid dysfunction, including hypothyroidism (slowed growth, fatigue) and hyperthyroidism (rapid development, anxiety).