Genetically determined classes of human blood that are based on the presence or absence of carbohydrates A and B on the surface of red blood cells. The ABO blood group phenotypes, also called blood types, are A, B, AB, and O.
A form of human dwarfism caused by a single dominant allele; the homozygous condition is lethal.
An alternative form of a gene.
A technique for diagnosing genetic defects while a fetus is in the uterus. A sample of amitotic fluid, obtained via a needle inserted into the amnion, is analyzed for telltale chemicals and defective fetal cells.
An individual who is heterozygous for a recessively inherited disorder and who therefore does not show symptoms of that disorder.
Chorionic villus sampling
A technique for diagnosing genetic defects while the fetus is in the uterus. A small sample of the fetal portion of the placenta is removed and analyzed.
Chromosome theory of inheritance
A basic principle in biology stating that genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns.
Inheritance pattern in which a heterozygote expresses the distinct trait of both alleles.
A type of inheritance in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable.
The fusion of sperm and egg derived from two different individuals.
An experimental mating of individuals differing at two genetic loci.
In a heterozygote, the allele that determines the phenotype with respect to a particular gene.
Duchenne Muscular Dystrophy
A human genetic disease caused by a sex-linked recessive allele; characterized by progressive weakening and a loss of muscle tissue.
Trait results from interaction among products of 2 or more gene pairs; a gene interaction where one gene suppresses the effect of another gene that is at a different locus on the chromosome.
The offspring of two parental (P generation) individuals; F1 stands for first filial.
The offspring of the F1 generation; F2 stands for second filial.
The scientific study of heredity and hereditary variations.
The genetic makeup of an organism.
Having two different alleles for a given gene.
Having two identical alleles for a given gene.
A human genetic disease caused by a dominant allele; characterized by uncontrollable body movements and degeneration of the nervous system; usually fatal 10 to 20 years after the onset of symptoms.
The offspring of parents of two different species or of two different varieties of one species; the offspring of two parents that differ in one or more inherited traits; an individual that is heterozygous for one or more pairs of genes.
Mating between close relatives.
A type of inheritance in which the phenotype of a heterozygote (Aa) is intermediate between the phenotypes of the two types of homozygotes (AA and aa).
Law of independent assortment
A general rule in in inheritance that when gametes form during meiosis, each pair of alleles for a particular characteristic segregate independently; also known as Mendel's second law of inheritance.
Law of segregation
A general rule in inheritance that individuals have two alleles for each gene and that when gametes form by meiosis, the two alleles separate, and each resulting gamete ends up with only one allele of each gene; also known as Mendel's first law of inheritance.
Linked genes (know ratio)
Genes located on the same chromosome that tend to be inherited together.
An experimental mating of individuals differing at one genetic locus.
Inheritance of quantitative traits or polygenic inheritance refers to the inheritance of a phenotypic characteristic that varies in degree and can be attributed to the interactions between two or more genes and their environment.
The parent individuals from which offspring are derived in studies of inheritance (P stands for parental).
A family tree representing the occurrence of heritable traits in parents and offspring across a number of generations.
The expressed traits of an organism.
The control of more than one phenotypic characteristic by a single gene.
The additive effect of two or more gene loci on a single phenotypic characteristic.
A diagram used in the study of inheritance to show the results of random fertilization.
In a heterozygous individual, the allele that has no noticeable effect on the phenotype.
Red-green color blindness
A category of common, sex-linked human disorders involving several genes on the X chromosome; characterized by a malfunction of light-sensitive cells in the eyes; affects mostly males but also homozygous females.
THe fusion of sperm and egg produced by the same individual organism.
A chromosome that determines whether an individual is male or female.
Sex linked gene
A gene located on a sex chromosome.
The mating between an individual of unknown genotype for a particular characteristic and an individual that is homozygous recessive for that same characteristic.
Referring to organisms for which sexual reproduction produces offspring with inherited traits identical to those of the parents; the organisms are homozygous for the characteristics under consideration.
A technique for examining a fetus in the uterus. High-frequency sound waves echoing off the fetus are used to produce an image of the fetus.