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BIOL 114
Ch 9: Patterns of Inheritance
Term | Definition |
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ABO blood groups | 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. |
achondroplasia | A form of human dwarfism caused by a single dominant allele. The homozygous condition is lethal. |
alleles | An alternative version of a gene. |
Carrier | An individual who is heterozygous for a recessively inherited disorder and who therefore does not show symptoms of that disorder. |
character | A heritable feature that varies among individuals within a population, such as flower color in pea plants. |
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. |
codominance | The expression of two different alleles of a gene in a heterozygote. |
dihybrid cross | A mating of individuals differing at two genetic loci. |
dominant allele | In a heterozygote, the allele that determines the phenotype with respect to a particular gene. |
F1 generation | The offspring of two parental (P. generation) individuals. F1 stands for first filial. |
F2 generation | The offspring of the F1 generation. F2 stands for second filial. |
Genetics | The scientific study of heredity (inheritance). |
genotype | The genetic makeup of an organism. |
Hemophilia | A human genetic disease caused by a sex-linked recessive allele and characterized by excessive bleeding following injury. |
Heredity | The transmission of traits from one generation to the next. |
heterozygous | Having two different alleles for a given gene. |
homozygous | Having two identical alleles for a given gene. |
Huntington's disease | 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. |
hybrids | 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. |
hypercholesterolemia | An inherited human disease characterized by an excessively high level of cholesterol in the blood. |
incomplete dominance | 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 of inheritance, first proposed by Gregor Mendel, that states that when gametes form during meiosis, each pair of alleles for a particular character segregate (separate) independently of each other pair. |
law of segregation | A general rule of inheritance, first proposed by Gregor Mendel, that states that the two alleles in a pair segregate (separate) into different gametes during meiosis. |
linkage map | A map of a chromosome showing the relative positions of genes. |
linked genes | Genes located close enough together on a chromosome that they are usually inherited together. |
locus | The particular site where a gene is found on a chromosome. Homologous chromosomes have corresponding gene loci. |
monohybrid cross | A mating of individuals differing at one genetic locus. |
P generation | The parent individuals from which offspring are derived in studies of inheritance. P stands for parental. |
pedigree | A family tree representing the occurrence of heritable traits in parents and offspring across a number of generations. |
phenotype | The expressed traits of an organism. |
pleiotropy | The control of more than one phenotypic character by a single gene. |
polygenic inheritance | The additive effect of two or more genes on a single phenotypic characteristic. |
Punnett square | A diagram used in the study of inheritance to show the results of random fertilization. |
recessive allele | In heterozygotes, the allele that has no noticeable effect on the phenotype. |
recombination frequency | With respect to two given genes, the number of recombinant progeny from a mating divided by the total number of progeny. Recombinant progeny carry combinations of alleles different from that seen in either of the parents as a result of independent assortment of chromosomes and crossing over |
Red-green colorblindness | A category of common sex-linked human disorders involving several genes on the X chromosome and characterized by a malfunction of light-sensitive cells in the eyes; affects mostly males but also homozygous females. |
rule of multiplication | A rule stating that the probability of a compound event is the product of the separate probabilities of the independent events. |
sex-linked gene | A gene located on a sex chromosome. |
sickle-cell disease | A genetic disorder in which the red blood cells have abnormal hemoglobin molecules and take on an abnormal shape. |
testcross | The mating between an individual of unknown genotype for a particular character and an individual that is homozygous recessive for that same character. |
trait | A variant of a character found within a population, such as purple flowers in pea plants. |
true-breeding | 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. |
wild-type trait | The trait most commonly found in nature. |