Located in the nucleus, they are made of DNA and protein.


characteristic that is inherited; can be either dominant or recessive


They are a section of DNA which codes for making a particular protein. They determine your characteristics.


Different variations of a gene. (e.g. F, f)

dominant allele

An allele that is always expressed (shown) if it is part of the genotype. (E.g. F)

recessive allele

An allele that is ONLY expressed (shown) if two are present (e.g. ff)


Deoxyribonucleic acid - carries the instructions for making proteins.

diploid cell

A cell which has two of each kind of chromosome.

haploid cell

A cell which has only one of each kind of chromosome (e.g. egg or sperm).

stem cell

A cell that has the potential to become any one of a variety of types of cells

homologous chromosome

These are chromosomes which carry genes for the same characteristics in the same place.


Having two of the same alleles for a gene (e.g. ff, FF)


Having two different alleles for a gene (e.g. Ff)


The alleles that you have. (e.g. Ff, ff, FF)


The features you have which depend on your genotype. (E.g. blonde or black hair)


When neither of the alleles is dominant or recessive but both have an effect on the phenotype of a heterozygous organism. (E.g. a red and white carnation cross pollinate to produce a pink carnation)

true breeding

Homozygous - parents that always produce offspring with the same characteristic as themselves.

Down's syndrome

A condition where a person has an extra copy of Chromosome 21.


When there is a problem in meiosis or in the copying of the DNA in cells, it results in mutations → the genetic code is changed.


A group of genetically identical organisms

amino acids

The building blocks of proteins

cystic fibrosis

Caused by an unusual protein that makes too much mucus in the lungs.


The average period , considered about 30 years, during which children are born, grow up, become adults and start to have own children


Passing on of characteristics from parent to offspring


a molecule that is made up of amino acids and that is needed to build and repair body structures and to regulate processes in the body.


a specific sequence of three adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid

nitrogen bases

The chemicals that make up the rungs of the DNA ladder - adenine, thymine, guanine, cytosine


The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group.

double helix

Twisted ladder shape of DNA, formed by two nucleotide strands twisted around each other


agents, such as chemicals or radiation, that damage or alter genetic material (DNA) in cells

gene expression

conversion of the information encoded in a gene first into messenger RNA and then to a protein


(genetics) the process whereby DNA makes a copy of itself before cell division


Reproductive cells, called ova and sperm)


The study of heredity

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