genetics level 1

DNA (Deoxyribonucleic Acid)

The double-helix molecule made of nucleotides that carries all genetic information in living organisms

Nucleotide

The basic building block of DNA made up of a sugar, phosphate group, and a nitrogen base

Base Pair

The complementary nitrogen bases that hold the DNA strands together A pairs with T and C pairs with G

Gene

A segment of DNA on a chromosome that codes for a specific protein or characteristic

Allele

An alternative version or form of a gene e.g. brown vs. blue eyes

Chromosome

A threadlike structure made of DNA molecules that contains many genes

Triplet

A sequence of three DNA bases that codes for a specific amino acid

Protein

A large chemical made of amino acids, folded into a specific shape, which determines physical and physiological traits

Genotype

The specific combination of alleles an organism has for a gene e.g. Bb

Phenotype

The observable physical or behavioural characteristics of an organism, resulting from its genotype interacting with the environment.

Homozygous (Purebred):

Having two identical alleles for a particular gene

Heterozygous

Having two different alleles for a particular gene

Dominant Allele

An allele that is always expressed in the phenotype even if only one copy is present

Recessive Allele

An allele that is only expressed in the phenotype when two copies are present

Trait / Characteristic

A genetically determined feature or physical/behavioural attribute of an organism.

Mitosis

A type of cell division that produces two genetically identical daughter cells

Meiosis

A type of cell division that produces four genetically unique haploid gametes with half the normal number of chromosomes

Gamete

A sex cell containing a haploid number of chromosomes.

Zygote

A fertilized egg cell formed by the union of a sperm and an egg

Fertilisation

The random fusion of a sperm and an egg, restoring the diploid number and creating new allele combinations in each new offspring

Sexual Reproduction

Reproduction involving two parents, combining genetic material from each parent to produce genetically unique offspring

Asexual Reproduction

Reproduction involving a single parent, producing genetically identical offspring

Clone

An organism that is an exact genetic copy of another

Genetic Variation

The differences in DNA/phenotypes among individuals within a population or species.

Mutation

A permanent, random change in the base sequence of DNA, which can create a new allele

Independent Assortment / Crossing Over

Processes during meiosis where chromosomes shuffle and exchange sections, increasing genetic variation in gametes.

Punnett Square

A grid diagram used to predict the probability or expected ratios of genotypes and phenotypes in offspring from a genetic cross.

Pedigree Chart

A family tree diagram that tracks the inheritance of a specific trait or phenotype across multiple generations.

Environment

External non-genetic factors that can influence how a phenotype is expressed.

Population

A group of organisms of the same species living in a specific area at the same time