Genetics, Evolution, and Chemistry: Key Concepts for Biology and Chemistry

Nucleotide

The basic building block of DNA.

Phosphate group

Forms the backbone of DNA.

Deoxyribose sugar

A 5-carbon sugar that connects the phosphate and base.

Nitrogenous base

One of four types (A, T, C, G) in DNA.

Complementary Base Pairing Rule

A pairs with T and C pairs with G.

Meiosis

The cell division process that produces gametes (sperm and egg cells).

Diploid

A cell with two sets of chromosomes (2n).

Haploid

A cell with one set of chromosomes (n).

Crossing over

The exchange of genetic material during meiosis.

Independent assortment

Random distribution of chromosomes during meiosis.

Dominant allele

Always expressed in the phenotype if present (e.g., A).

Recessive allele

Only expressed when both alleles are recessive (e.g., aa).

Genotype

The genetic makeup (e.g., TT, Tt, tt).

Phenotype

The physical expression or appearance (e.g., tall or short).

Punnett Square

A diagram used to predict the outcome of a genetic cross.

DNA Mutation

Changes in the DNA sequence that can create new traits.

Original fossils

Actual remains (e.g., bone, tooth, shell).

Replacement fossils

Minerals replace original material (e.g., petrified wood).

Carbon film fossils

Thin carbon layer left behind (e.g., plant imprints).

Indirect fossils

Evidence of activity (e.g., footprints, burrows).

Index Fossils

Remains of species that were widespread, abundant, and lived for a short geological period.

Transitional fossils

Fossils that show features between groups (e.g., Archaeopteryx).

Natural Selection

The process where individuals with favorable traits survive and reproduce.

Variation

Provides raw material for natural selection.

Genetic diversity

Populations with greater genetic diversity are more adaptable to change or disease.

Peppered moth

Dark moths survived industrial pollution; lighter ones declined.

Insecticide resistance

Some insects evolved resistance to insecticides.

Antibiotic resistance

Overuse of antibiotics leads to resistant strains of bacteria.

Species

A group of organisms that can interbreed and produce fertile offspring.

Speciation

The formation of a new species due to isolation and genetic change.

Biodiversity

The variety of life on Earth — essential for ecosystem stability.

Atomic Symbols

Written as: Element symbol - Mass number over Atomic number.

Atoms of Common Elements

H: 1 protons, 1 electrons, 0 neutrons; C: 6 protons, 6 electrons, 6 neutrons; O: 8 protons, 8 electrons, 8 neutrons; Na: 11 protons, 11 electrons, 12 neutrons.

Electron Configurations

Electrons fill energy levels around the nucleus: First shell: 2, Second: 8, Third: 8.

Cations

Positive ions - formed when atoms lose electrons (e.g., Na⁺).

Anions

Negative ions - formed when atoms gain electrons (e.g., Cl⁻).

Periodic Table Structure

Groups (vertical): Elements with similar chemical properties and same number of valence electrons; Periods (horizontal): Elements with the same number of electron shells.

Atomic number trend

Increases left → right, top → bottom.

Reactivity of Metals

More reactive down a group.

Reactivity of Non-metals

More reactive up a group.

Complete Combustion

Hydrocarbon + Oxygen → Carbon dioxide + Water.

Incomplete Combustion

Hydrocarbon + Limited Oxygen → Carbon monoxide + Carbon + Water.

Corrosion

Iron + Oxygen + Water → Iron oxide (rust).

Photosynthesis

Carbon dioxide + Water → Glucose + Oxygen.

Respiration

Glucose + Oxygen → Carbon dioxide + Water + Energy.

Collision Theory

Particles must collide with enough energy (activation energy) and the correct orientation to react.

Law of Conservation of Energy

Energy cannot be created or destroyed, only transformed.