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Chromosomes are made from DNA. Genes are short sections of DNA. DNA carries genetic code that determines characteristics of a living organism.

Mitosis makes identical cells, meiosis makes gametes.

Genetic diagrams show how characteristics are inherited. Alleles can be recessive, dominant or codominant genes.

Sex is controlled in humans by the X and Y chromosomes. Genetic screening involves testing people or groups of people for the presence of a particular allele or other genetic abnormality.

Genetic engineering is a process that modifies the genome of an organism to introduce desirable characteristics.

Organisms of the same species vary in many ways. There are two types of variation – continuous and discontinuous. Natural selection explains how evolution occurs.