Question

genes are segments of dna that are the basic unit of heredity. they are passed on from parent to offspring.
the gene form of a trait is called a(n) allele.
an organisms allele combination is called the genotype.
the physical appearance of an organism is called the phenotype.
complete
there are two types of alleles. an allele that masks another is the dominant allele. the one that is masked is called the recessive allele.
an organism that has the same alleles for a particular trait is
an organism that has different alleles for a particular trait is
done

Explanation:

Alleles are different forms of a gene. Genotype refers to the genetic makeup (allele combination). Phenotype is the physical expression. Dominant alleles mask recessive ones. Homozygous means same alleles for a trait; heterozygous means different alleles.

Answer:

An organism that has the same alleles for a particular trait is homozygous. An organism that has different alleles for a particular trait is heterozygous.