Genetic Inheritance

• Gametes are sex cells, such as sperm and ovum, in animals, and pollen nucleus and ovum in plants.
• Phenotype is the term used to describe the characteristics of an organism as seen or observed, such as eye colour or blood type.
• Chromosomes are thread-like structures of DNA, carrying genetic information in the form of genes, and are located in the nucleus of cells.
• Genes are short lengths of DNA found on chromosomes, and code for specific proteins.
• Alleles are different versions of a particular gene.
• A dominant allele is always expressed, even if only one copy is present.
• The combination of alleles that control each characteristic is called the genotype.
• The observable characteristics of an organism are determined by the genotype.
• If the two alleles of a gene are the same, the individual is described as being homozygous (homo = same).
• A recessive allele is only expressed if two copies are present, therefore no dominant allele is present.
• If the two alleles of a gene are different, the individual is described as being heterozygous (hetero = different).