Autosomes: chromosomes not involved in specifying sex.
Allele: an alternative form of a gene.
Chromosome: a physically organised form of DNA in a cell. The fowl has 38 pairs of autosomes and a pair of sex chromosomes.
Diploid: having a pair of each type of chromosome.
Dominant: the allele that generates the phenotype in a heterozygous organism.
Expression: the process by which the information in a gene is made into a functional gene product.
Gametes: the haploid germ cells; sperm in males, eggs (ova) in females.
Genotype: the genetic composition of an organism.
Haploid: having a single set of chromosomes.
Heterozygote: has two different alleles at a given locus (heterozygous).
Homozygote: has two identical alleles at a given locus (homozygous).
Incomplete dominance: in a heterozygote both alleles at a locus are partially expressed, resulting in an intermediate phenotype.
Linkage: measure of the probability of two genes being transmitted together to offspring.
Locus: the particular point on a chromosome where a gene is located.
Meiosis: the process of cell division by which gametes are formed.
Mendel’s laws: all alleles for a character segregate independently of one another and each is represented in 50% of the gametes and all gametes have an equal chance of fertilisation.
Phalanges: the bones of a finger or toes.
Phenotype: the observed physical and physiological traits of an organism, produced by the genotype in conjunction with the environment.
Recessive: an allele that only generates a phenotype if it is homozygous.
Sex chromosomes: chromosomes which determine the sex of an individual. ZW in females and ZZ in males. The W chromosome in females is very small and does not carry the same genetic information as the Z chromosome.
Sex linked: carried by a sex chromosome.
Wildtype: allele(s) responsible for the ‘normal’ (non-mutant) phenotype.