| 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) |
GCSE Biology > Genetic Terminology