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45 terms

Chapter 9: Patterns of Inheritance Vocabulary

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Genetics
Scientific study of heredity and hereditary variations
Heredity
Transmission of characteristics from parents to offspring
Self-fertilization
Fusion of sperm and egg that are provided by the same individual
Cross-fertilization
Fusion of sperm and egg provided by two different individuals
True-breeding
Organism for which sexual reproduction produces offspring with inherited traits identical to those of the parents; organisms are homozygous for the characteristic under consideration
Hybrid
Offspring of two parents that differ in one or more inherited traits; an individual that is heterozygous for one or more pairs of genes
Genetic cross
Cross-fertilization of two different varieties of an organism or two different species; hybridization
P generation
Parent individuals from which offspring are derived in inheritance studies; P = parental
F1 generation
Offspring of two P generation individual; F = filial
F2 generation
Offspring of two F1 generation individuals
Monohybrid cross
An experimental mating of individuals differing at one genetic locus
Alleles
Alternative form of a gene
Homozygous
Having two identical alleles for a given gene
Heterozygous
Having tow different alleles for a given gene
Dominant allele
In a heterozygote, allele that determines the phenotype with respect to a particular gene
Recessive allele
In a heterozygote, allele that has no noticeable effect on the phenotype
Law of segregation
Individuals have two alleles for each gene and that when gametes form by meiosis, the two alleles separate and each resulting gamete possesses only one allele of each gene
Punnett square
Diagram used in the study of inheritance to show the results of random fertilization
Phenotype
The expressed traits of an organism; outward appearance
Genotype
Genetic makeup of an organism
Locus
Particular site where a gene is found on a chromosome; homologous chromosomes have corresponding gene loci
Dihybrid cross
Experimental mating of individuals differing at two loci
Law if independent assortment
General rule of inheritance that when gametes form during meiosis, each pair of alleles for a particular characteristic segregate independently
Rule of multiplication
The probability of a compound event is the product of the separate probabilities of the independent events
Wild-type traits
Traits most commonly found in nature
Pedigree
Family tree representing the occurrence of heritable traits in parents and offspring across a number of generations
Carrier
Individual who is heterozygous for a recessive inherited disorder and who does not show symptoms of that disorder
Inbreeding
Mating of close relatives
Achondroplasia
Form of human dwarfism caused by a single dominant allele; homozygous condition is lethal
Huntington's disease
Human genetic disease caused by a dominant allele and characterized by uncontrollable body movements and degeneration of the nervous system; usually fatal 10-20 years after onset of symptoms
Incomplete dominance
Type of inheritance in which the phenotype of a heterozygote is intermediate between the two types of homozygous phenotypes
Hypercholesterolemia
Inherited human disease characterized by an excessively high level of cholesterol in the blood
ABO blood groups
Genetically determined human blood classes that are based on the presence or absence of carbohydrates A and B in the surface of red blood cells
Codominance
Expression of two different alleles of a genotype in a heterozygote
Pleiotropy
Control of more than one phenotypic characteristic by a single gene
Sickle-cell disease
Genetic disorder in which red blood cells have abnormal hemoglobin molecules and take on an abnormal shape
Polygenic inheritance
The additive effect of two or more gene loci on a single phenotypic characteristic
Chromosome theory of inheritance
Basic biological principle stating that genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns
Linked genes
Genes located closely enough on a chromosome that they are usually inherited together
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 different combinations of alleles than their parents as a result of independent assortment and crossing over
Linkage map
Map of a chromosome showing the relative position of genes
Sex-linked gene
Gene located on a sex chromosome
Red-green color blindness
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 eye; affects mostly males but also homozygous females
Hemophilia
Sex-linked human genetic blood disorder caused by a recessive allele that affects proper blood clotting
Duchenne muscular dystrophy
Human genetic disease caused by sex-linked recessive allele and characterized by progressive weakening and a loss of muscle tissue