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. |
