Question

this passage describes the iridescent scales trait in bettas: a betta, or siamese fighting fish, is a popular aquarium pet. many bettas have shiny iridescent scales, which contain tiny crystals that reflect light. these crystals cause the fishs color to look slightly different when seen from different angles. some bettas are covered in mostly iridescent scales. other bettas have mostly plain, non - iridescent scales. in a group of bettas, some individuals have mostly iridescent scales and others have mostly plain scales. in this group, the gene for the iridescent scales trait has two alleles. the allele i is for mostly iridescent scales, and the allele i is for mostly plain scales. sandy is a betta from this group. sandys phenotype for the iridescent scales trait is mostly plain scales. sandys genotype for the iridescent scales gene is ii. based on this information, complete the following statement. sandy is for the iridescent scales gene. homozygous heterozygous

Explanation:

A homozygous individual has two identical alleles for a gene. Since Sandy's genotype for the iridescent - scales gene is $ii$ (two identical alleles), Sandy is homozygous. A heterozygous individual has two different alleles for a gene.

Answer:

homozygous