Genetics

Alleles

Different versions of the same gene

Carrier

A person who does not show symptoms of a disease but carries the recessive allele for that disease. This means they could possibly pass it onto their offspring

Chromosomes

Molecules made of DNA that are found in the nucleus of a cell. Human body cells have 46 chromosomes

Continuous variation

A feature that can vary, for example, height or weight

Crossing over

Crossing over occurs during meiosis when homologous chromosomes are lined up and parts of the chromosome are switched. The two chromosomes contain the same genes, but may have different forms of the genes.

Discontinuous variation

Variation where there are limited options, for example tongue rolling- you can either tongue roll or you cannot.

DNA

Deoxyribonucleic acid, found inside the nucleus of a cell and, carries the genetic information.

Dominant allele

The allele that shows up as a characteristic in an organism even if only one copy of the allele is present. It is represented by a capital letter

Double Helix

The twisted shape that DNA takes / has

Fertilisation

Fusing of egg(ova) and sperm to create zygote that will ultimately become a new individual

Gametes

Another name for sex cells, such as sperm and egg

Genes

Made up of DNA. They control an organism’s characteristics

Genetic marker

A DNA sequence with a known physical location on a chromosome

Gene tracking

A method for determining the inheritance of a particular gene in a family. It is used in the diagnosis of genetic diseases, such as cystic fibrosis and Huntington's disease.

Genetic variation

Differences in genes between individuals in a population, or between different populations.

Genomic variation

Differences in genomes (the complete set of genetic material) between individuals in a population, or between different populations.

Genotype

The combination of alleles that a person or organism has for a particular  trait.

Heredity

The passing of genes from parents to offspring

Heterozygous

Having two different alleles to code for a trait.  OR Having two different versions of the same gene.

Homologous chromosomes

Two chromosomes in a pair – one inherited from the mother and one from the father. For example, the two copies of Chromosome 1 in a cell would be referred to as homologous chromosomes.

Homozygous

Having two of the same alleles to code for a trait.

Meiosis

A form of cell division that creates gametes (sperm and eggs).

Mutation

A change in the structure of DNA

Natural Selection

A process where the organisms with the characteristics most suited to their environment are more likely to survive and pass on their genes.

Nucleotide

The building block of DNA.  It is made of a sugar, phosphate and base.

Nucleus

The central part of a cell, which contains the chromosomes.

Pedigree chart

Pedigree diagrams are used to show how a genetic condition is inherited in a family.

Phenotype

A term used to describe the appearance of an individual.

Phylogenetic tree

 A diagram that shows the lines of  descent of different species, organisms, or genes from a common ancestor.

Population

All the members of a single species that live in a habitat

Protein

A molecule made of amino acids that determine the structure and function of an organism. Genes code for protein molecules.

Punnett square

The Punnett square is a diagram used to predict the outcome of a particular genetic cross.

Recessive allele

The allele that shows up as a characteristic in an organism if contains the two copies of it.  It is represented by a lowercase letter.

Sexual reproduction

A type of reproduction that involves gametes from two parents and leads to variation in the offspring.