Term 1: Terminology Genetics 214
• Pure breeding: An individual that is homozygous for any allele.
• Independent Segregation: The equal likelihood of any gamete to receive one or the
other allelic copy of the paired unit factor.
• Independent assortment: Assumption that allows the use of probability rules for
determining multi-locus genotypic ratios in crosses where more than one trait is
investigated.
• Test cross: Mating an individual, showing the dominant phenotype, to an individual
showing the recessive phenotype to determine if the former is a carrier.
• Dominant: An allelic variant at a gene that masks the phenotypic effects of a different
allelic variant of the same gene.
• Recessive Lethal: Homozygosity for the null allele does not support life.
• Dominant lethal: lethal alleles may be dominant; hetro state also lethal
• Wild type: The allele (and resulting phenotype) that is most frequent in a population;
can be dominant or recessive.
• Co-dominance: Both allelic variants are expressed and detected in the phenotype
when an individual is heterozygous.
• Neutral mutation: A DNA allelic variant that does not have an impact on phenotypic
fitness.
• Null allele: A mutant allele that results in a completely dysfunctional protein.
• Incomplete dominance: Both allelic variants are expressed resulting in an
intermediate phenotype when an individual is heterozygous.
• Genetic anticipation: Phenotype severity or prominence becomes more evident with
each generation.
• Complimentary Epistasis: At least one dominant allele is needed at both loci to
exhibit the phenotype.
• Penetrance: 80% of the heterozygotes show the phenotype associated with a
dominant mutant allele.
• Complementation: Two mutations in different genes causes the same mutant
phenotype, in heterozygotes (for both genes) the wild type phenotype is restored.
• Pleiotropy: A gene is responsible for phenotypic development of coat colour in cats,
but also has an influence on temperament. One gene affects more then one
phenotypic character.
• Allele: Alternative versions of a gene that normally relates to difference in the
nucleotide base pair sequence.
• Genotype: The combination of gene copies that an individual has for a particular
gene or genomic region.
• Gene: Fundamental unit of heredity consisting of a series of nucleotide base pairs
that codes for a polypeptide or RNA molecule.
• Chromatid: One of the longitudinal subunits of a replicated chromosome
• Trait: An observable, measurable or classifiable characteristic that is determined by
heredity
• Haloid number: Typically, the total number of chromosomes in a gamete, that
contains only one member of an homologous pair.
• Centromere: A heterochromatic region of a chromosome that binds its sister
chromatids
• Locus: A specific chromosomal region in the genome.
• Phenotype: Alternative forms of an trait that is genetically determined
• Pure breeding: An individual that is homozygous for any allele.
• Independent Segregation: The equal likelihood of any gamete to receive one or the
other allelic copy of the paired unit factor.
• Independent assortment: Assumption that allows the use of probability rules for
determining multi-locus genotypic ratios in crosses where more than one trait is
investigated.
• Test cross: Mating an individual, showing the dominant phenotype, to an individual
showing the recessive phenotype to determine if the former is a carrier.
• Dominant: An allelic variant at a gene that masks the phenotypic effects of a different
allelic variant of the same gene.
• Recessive Lethal: Homozygosity for the null allele does not support life.
• Dominant lethal: lethal alleles may be dominant; hetro state also lethal
• Wild type: The allele (and resulting phenotype) that is most frequent in a population;
can be dominant or recessive.
• Co-dominance: Both allelic variants are expressed and detected in the phenotype
when an individual is heterozygous.
• Neutral mutation: A DNA allelic variant that does not have an impact on phenotypic
fitness.
• Null allele: A mutant allele that results in a completely dysfunctional protein.
• Incomplete dominance: Both allelic variants are expressed resulting in an
intermediate phenotype when an individual is heterozygous.
• Genetic anticipation: Phenotype severity or prominence becomes more evident with
each generation.
• Complimentary Epistasis: At least one dominant allele is needed at both loci to
exhibit the phenotype.
• Penetrance: 80% of the heterozygotes show the phenotype associated with a
dominant mutant allele.
• Complementation: Two mutations in different genes causes the same mutant
phenotype, in heterozygotes (for both genes) the wild type phenotype is restored.
• Pleiotropy: A gene is responsible for phenotypic development of coat colour in cats,
but also has an influence on temperament. One gene affects more then one
phenotypic character.
• Allele: Alternative versions of a gene that normally relates to difference in the
nucleotide base pair sequence.
• Genotype: The combination of gene copies that an individual has for a particular
gene or genomic region.
• Gene: Fundamental unit of heredity consisting of a series of nucleotide base pairs
that codes for a polypeptide or RNA molecule.
• Chromatid: One of the longitudinal subunits of a replicated chromosome
• Trait: An observable, measurable or classifiable characteristic that is determined by
heredity
• Haloid number: Typically, the total number of chromosomes in a gamete, that
contains only one member of an homologous pair.
• Centromere: A heterochromatic region of a chromosome that binds its sister
chromatids
• Locus: A specific chromosomal region in the genome.
• Phenotype: Alternative forms of an trait that is genetically determined
