3.17 Understand the meaning of the terms: dominant, recessive, homozygous, heterozygous, phenotype, genotype and codominance

Homozygous: two same alleles of a gene on each chromosome on a homologous pair
Heterozygous: one of each allele of a gene on each chromosome on a homologous pair
Rescessive: an allele only expressed if the dominant allele is absent or if [the recessive gene] is homozygous.
Dominant: an allele that always express itself whether it is heterozygous or homozygous


Homologous pair: a chromosome containing a maternal and paternal chromatid joined together. (these have the same gene but may have different alleles)
Chromatid: each of the two threadlike strands that chromosomes divide into during mitosis.