5.2 - Chromosomal Theory of Inheritance

gene

sequence of DNA that codes for a protein and thus determines a trait

allele

different versions of a gene

dominant

an allele that is always expressed when present

recessive

An allele that is only expressed in the phenotpye if there is not a dominant allele in the genotype is said to be recessive.

P generation

parental generation, the first two individuals that mate in a genetic 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

law of segregation

Mendel's first law, stating that the pairs of homologous chromosomes separate in meiosis so that only one chromosome from each pair is present in each gamete

law of independent assortment

Mendel's second law, stating that genes separate independently of one another in meiosis during gamete formation

principle of dominance

Mendel's second conclusion, which states that some alleles are dominant and others are recessive

one-trait cross

a cross between individuals that involves one pair of traits

two-trait cross

a cross between individuals that involves two pairs of traits

homozygous

having two identical alleles for a particular gene

heterozygous

having two different alleles for a particular gene

genotype

an organism's genetic makeup, or allele combinations.

phenotype

physical characteristics/appearance of an organism