SCI102 - Biology Definitons

Adaptations

Traits that help an organism survive.

Alleles

Different versions of the same gene.

Amino acids

Small molecules that join together to make proteins.

Asexual reproduction

One parent → identical offspring.

Cell division

When one cell splits into two.

Cells

Tiny building blocks that make up all living things.

Chromosomes

Packages of DNA found in cells.

Complementary base pairing rule

A pairs with T, and C pairs with G.

Cross breeding

Mixing different parents to get varied offspring.

Crossing over

Chromosomes swap bits of DNA during meiosis.

DNA

A long molecule that holds genetic instructions.

DNA profiling

Comparing DNA to identify individuals.

DNA Replication

Copying DNA before a cell divides.

DNA sequencing

Reading the order of DNA bases.

Dominant allele

Shows its trait even if only one copy is present.

Emigration

Leaving a population.

Endemic birds

Birds found only in one place.

Evolution

Change in a species over time.

Founder effect

Small group starts a new population → limited variation.

Gametes

Sex cells (sperm and egg).

Gene flow

Movement of alleles between populations.

Gene pool

All the alleles in a population.

Genes

Small sections of DNA that code for traits.

Genetic markers

Known DNA sequences used to identify genes.

Genetic screening

Testing DNA for diseases or traits.

Genetic variation

Different alleles in a population.

Genotypes

The allele combination (e.g., Hh).

Genotypic ratios

Ratio of genotype types (e.g., 1HH:2Hh:1hh).

Heterozygous

Two different alleles (Hh).

Homozygous

Two same alleles (HH or hh).

Independent assortment

Chromosomes mix randomly into gametes.

Inheritable traits

Traits passed on through DNA.

Meiosis

Cells

Migration

Moving into a population.

Mitosis

Cell division that makes identical body cells.

Mutations

Changes in DNA.

Natural selection

Best‑adapted individuals survive and reproduce.

Non‑inheritable traits

Traits caused by environment (e.g., scars).

Non‑random mating

Choosing mates based on traits.

Nucleotide

A small unit of DNA made of sugar + phosphate + base.

Pedigree charts

Family trees showing inherited traits.

Phenotypes

The physical trait you see (e.g., brown eyes).

Phenotypic ratios

Ratio of visible traits (e.g., 3 brown:1 blue).

Population

A group of the same species living in one area.

Population bottlenecks

Big drop in population → loss of variation.

Protein

A molecule that does jobs in the body (enzymes, hormones, structure).

Punnett squares

A grid used to predict offspring genotypes.

Pure breeding

Always produces the same trait (homozygous).

Purpose of Meiosis

To make gametes with half the chromosomes and create variation.

Random fertilisation

Any sperm can join with any egg.

Random mating

Mating without choosing specific traits.

Recessive allele

Only shows when two copies are present.

Selective pressure

Something that makes certain traits more useful (predators, climate).

Sexual reproduction

Two parents → varied offspring.

Somatic cells

Body cells (non‑sex cells).

Sources of genetic variation

Mutations, meiosis, random fertilisation.

Species

A group that can breed and produce fertile offspring.

Types of adaptations

Structural (body), behavioural (actions), physiological (internal).

Types of mutations

Substitution, insertion, deletion.

Variation

Differences between individuals.