Inheritance Flashcards
Allele
One or two or more forms of a gene located in the same position on homologous chromosomes.
Homozygous
Describes a condition in which both alleles for the gene are the same.
Purebred
An organism that is homozygous for a trait and this carries the same phenotype as the parents.
Heterozygous
Each allele for the characteristic exhibiting a different expression.
Hybrid (Genetic)
Heterozygote for a characteristic; plant or animal resulting from a cross between parents that are genetically unalike for that trait.
Wild Type
The most common phenotype for a feature in a population.
Dominant Trait
The particular trait of a characteristic that is expressed in the phenotype of a heterozygous individual.
Dominant Allele (Autosomal Dominant)
An allele for a gene that overrides the effects of the recessive allele in the heterozygous condition; can be autosomal or sex-linked.
Recessive Trait
trait due to an allele that can be masked by the dominant allele in the heterozygous condition but expressed in the homozygous condition.
Recessive Allele (Autosomal Recessive)
An allele found on an autosomal chromosome that can be masked by its dominant form in the heterozygous condition; can be autosomal or sex-linked.
Punnett Square
Mathematical device used to calculate probabilities of genetic crosses.
Monohybrid Cross
Genetic cross between two individuals, both heterozygous for a specific trait.
Dihybrid Cross
Genetic cross between two individuals, both heterozygous for two specific traits.
Dihybrid Ratio
Predicted ratio of offspring obtained from a cross between individuals simultaneously for two characteristics.
Product Rule
A law of probability, stating that the change of two independent events occurring together is equal to the chance of one event occurring alone multiplied by the chance of the other event occurring alone.
Frequency Histogram
A accurate representation of the distribution of numerical data and is an estimate of the probability frequency distribution of a continuous variable (quantitative variable).
Test Cross
A cross between an organism displaying the recessive trait of a characteristic and one showing the dominant trait, to determine whether the dominant phenotype is due to a homozygous genotype; this only applies if a large number of offspring are produced.
Modifier Genes
Genes that influence the expression of another gene.
Codominance
Genetic inheritance of two or more traits of a characteristic, each of which expressed in the phenotype.
Intermediate Dominance (Partial Dominance or Incomplete Dominance)
A pattern of inheritance in which neither allele for a characteristic completely masks the effects of the other; results in a blending of traits for the characteristics.
Multiple or Ploy Alleles
The inheritance of a characteristic governed by more than two allelic forms, e.g. blood groups.
Agglutination
Sticking together of incompatible cells, e.g. by different ‘groups’ of red blood cells.
Universal Donor
A person with type O blood, which has no antibodies to antigens A and B; thus this blood can be donated in small quantities to individuals of all other blood groups.
Universal Recipient
A person with type AB blood, which has both A na dB antigens, so can receive small quantities of all other blood groups.
Polygenic (or Multiple Gene) Inheritance
Inheritance from a set of genes that together control quantitative character such as height.
Continuous Variation
A variety of phenotypes as a result of more than one gene contributing to a characteristic.
Gene Complexes
Two or more genes interacting to determine the phenotypic expression of a characteristic.
Epistasis
(=Standing upon) where the phenotypic expression of one gene is masked by another gene.
Phenylketonuria (PKU)
A homozygous recessive genetic disease in which one enzyme required for the normal breakdown of phenylalanine is lacking.
Sex-Linked Genes
Genes on the X chromosome.
Carrier
An individual (female in humans) who is heterozygous for a sex-linked gene or an individual who is infected by a pathogen but does not display the symptoms.
Colour Defective Vision
Inability of individuals to distinguish the colours red and green.
Haemophilia
A group of disorders in which the blood does not clot normally.
Barr Body
Inactive X chromosome in the cells of female mammals.
X Inactivation
The condensation, and this inhibition, of one of the paris of X chromosomes in the female vertebrates.
Family Tree
A chart showing the ancestry, descent and relationships between all members of a family or other genealogical group.
Holandric Genes
Genes found on a vertebrate Y chromosome.
