| DNA | The molecule which contains genes. It’s shaped like a double helix (a spiral) |
| Chromosomes | Found in the cell nucleus: X-shaped things made up of long coils of DNA |
| Chromatids | The separate arms of the chromosomes |
| Centromere | Area at centre of chromosome where the separate arms meet |
| Gene | Section of DNA molecule |
| Allele | A gene, but there are two types of alleles |
| Homozygous | An organism with two alleles the same for a particular gene (e.g. HH or hh) |
| Heterozygous | An organism with two alleles that are different (e.g. Hh) |
| Dominant | An allele/gene that determines the characteristics in the organism (dominant over the recessive allele) |
| Recessive | Does not usually affect the phenotype of the organism |
| Genotype | The description of the GENES you have (e.g. MM or Hh etc…) |
| Phenotype | The description of your PHYSICAL ATTRIBUTES (e.g. hair colour) |
| Mitosis | Cell division – one cell splits into two identical cells |
| Meiosis | Cell division – produces haploid cells (the sperm / egg cells) |
| Diploid | Describes a cell with the full number of chromosomes (46 for humans) |
| Haploid | Describes a cell with half the full number of chromosomes |
| Zygote | A newly formed life just after fertilisation of the egg by the sperm |
| Gamete | A sperm / egg cell (both haploid) |
