Gene Every human has a gene for eye color. Gene: A piece of DNA that codes for a protein.

Phenotype All of the tall tomato plants show the same phenotype. Phenotype is the physical appearance of a certain trait

Genotype A tomato plant that is Tt and TT, however, do not share the same genotype. Genotype: the alleles for a gene (trait) an organism has

Allele The allele “T” produces tall plants. Alleles: different forms of a gene for a specific trait

Homozygous homozygous: having two identical alleles of a gene/trait Both parents gave curly hair alleles, so their baby was homozygous for curly hair.

Heterozygous Heterozygous: having two different alleles of a gene/trait One parent gave the baby an allele for brown hair, and the other gave the baby an allele for red hair. The baby was heterozygous for hair color.

Dominant Brown hair alleles are dominant over blond hair alleles. Dominant: allele that will always affect phenotype when present (homozygous & heterozygous)

Recessive Blue eyes are recessive to all other eye color alleles. Recessive: allele that will only have an effect on phenotype if there are two copies (homozygous)

Co-dominant Brown eyes and green eyes can be co-dominant in people with hazel eyes. Co-dominant: both alleles show up in the phenotype.