Term | Definition |
Gene | A section of a chromosome (or DNA ) which codes for a protein to produce a characteristic. |
Chromosome | A coiled up piece of DNA. Chromosomes are found in the nucleus of a cell. |
D.N.A. | (Deoxyribonucleic acid). Contains all an organism's genetic information. This molecule is what chromosomes are made of. |
Alleles | Alternative forms of a gene. There are often dominant and recessive alleles for the same gene. |
Heterozygous | A pair of alleles where there is a dominant and a recessive allele. |
Homozygous | A pair of alleles where either both genes are recessive or both genes are dominant. |
Dominant | A gene whose characteristic always appears even if only one copy is inherited. |
Recessive | A gene whose characteristic only appears if copies are inherited from both parents. |
Mutation | A ‘mistake’ in a gene or chromosome which usually occurs when it replicates. |
Gamete | These are reproductive cells. They contain half the number of chromosomes of a body cell. Animal gametes are egg and sperm, plant gametes are pollen and ovule. |
Mitosis | This type of cell division occurs in body cells. The chromosomes replicate so that the two new cells both have the same genetic composition as the original cell. |
Meiosis | This type of cell division produces gametes. The chromosomes divide so that each new cell has half the number of the original cell. |
Genotype | The combination of alleles that an individual has e.g. homozygous dominant, BB. |
Phenotype | The physical appearance of an individual as a result of their genotype. |
Asexual reproduction | This is reproduction with only one parent. The offspring are clones of their parent. |
Sexual reproduction | Reproduction where there are two parents and there is genetic recombination. |
Continuous characteristic | A characteristic which shows a continuous range in a population e.g height |
Discontinuous (or discrete) characteristic | A characteristic which has 2 possible outcomes e.g. tongue rolling |
Nucleus | The organelle in which genetic information is found within a cell. |
Variation | The difference between organisms |
Karyotype | A photo of the chromosomes in an organism, organised in pairs from longest to shortest |