BIO Ch.9-10 SG Vocab

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.