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what are alleles?
different forms of the same gene
can both copies of a gene be different?
yes, each copy may be a different allele
what causes genetic variation in humans?
different combinations of alleles in each person
what does it mean if an organism is homozygous for a gene?
it has two identical alleles for that gene
what does it mean if an organism is heterozygous for a gene?
it has two different alleles for that gene
how many copies of each chromosome do gametes have?
only one copy of each chromosome
how many copies of a gene do gametes contain?
only one copy of each gene
when is a recessive characteristic seen?
only if both alleles are recessive
what is an organism’s genotype?
the combination of alleles it has
what is an organism’s phenotype?
the physical characteristics an organism displays