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Glossary
| Allele |
Different copies of the ame gene. You inherit one allele from your mother and one from your father. |
| Autosome | Any chromosome other than the sex chromosomes. |
| Chromosome |
Structures found in the cell which contain a package of the cell's DNA. |
| Dominant |
Chromosomes come in pairs and a normal human cell has 46 chromosomes: 22 pairs of autosomes and two sex chromosomes. |
| Gene |
Sub-unit of DNA which codes for a specific protein. The translated protein performs a unique function in the cell. |
| Genome |
The entire group of genes possessed by an organism. |
| Genotype |
The actual genes carried by the individual, not necessarily what is expressed (as opposed to phenotype). |
| Heterozygote |
Organism carrying two different alleles of the same gene (adjective is heterozygous). |
| Homozygote |
Organism carrying two of the same allele of a gene (adjective is homozygous). |
| Incomplete penetrance |
Occurs when a gene only sometimes results in disease. |
| Mutation | A change in the nucleotide sequence of a gene. |
| Nucleotide |
A sub-unit of DNA or RNA, consisting of one chemical base plus a phosphate molecule and a sugar molecule. There are four different chemical bases: adenine, guanine, cytosine, and thymine. Nucleotides pair up via hydrogen bonds in the DNA strand to form the double helix. |
| Recessive |
When a gene is inherited in a recessive fashion, the mutated allele will not be expressed if there is a normal copy. You must possess two recessive alleles to show the mutated phenotype. eg. cystic fibrosis (opposite of dominant). |
| Penetrance | The likelihood that a given gene will actually result in disease. |
| Phenotype | The physical characteristics into which genes are translated (eg. a carrier of the CF gene and a non-carrier have the same phenotype). |
| Polymorphism | Different forms of the same gene or allele. |
| Sex chromosome | Chromosomes that contain the genes that distinguish the sexes. In humans, females have two "X" chromosomes, and males have one "X" and one "Y" chromosome. |
| Tumour-suppressor gene |
A gene that normally suppresses cell growth but, if missing or mutated, a cell is allowed to divide uncontrolled. |
