random fertilization
source of genetic variation caused by the unlimited number of possible sperm & egg combinations
crossing over
exchange of genetic material between homologous chromosomes during prophase I of meiosis
true-breeding
term used to describe organisms that produce offspring identical to themselves
carrier
A person whose genotype includes a gene that is not expressed in the phenotype.
testcrosses
way to determine unknown genotypes
parent generation
P generation where all the offspring get thier traits from, The first generation of a cross.
F1 generation
the first generation of offspring obtained from an experimental cross of two organisms
F2 generation
the second generation of offspring, obtained from an experimental cross of two organisms; the offspring of the F1 generation
homozygous
having two identical alleles for a trait
heterozygous
having two different alleles for a trait
dominant allele
An allele whose trait always shows up in the organism when the allele is present.
recessive allele
An allele that is hidden whenever the dominant allele is present
genotype
An organism's genetic makeup, or allele combinations.
phenotype
physical characteristics of an organism
gene locus
Location of a gene on a chromosome
pedigree
A diagram that shows the occurrence of a genetic trait in several generations of a family.
incomplete dominance
A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a blending of the parental traits.
multiple alleles
A gene that has more than two alleles
codominance
A condition in which both alleles for a gene are fully expressed
pleiotropy
A single gene having multiple effects on an individuals phenotype
polygenic inheritance
occurs when multiple genes determine the phenotype of a trait
karyotype
A display of the chromosome pairs of a cell arranged by size and shape.
nondisjunction
An error in meiosis or mitosis in which members of a pair of homologous chromosomes or a pair of sister chromatids fail to separate properly from each other.