What does it mean for an individual to be homozygous?

An individual being homozygous means that they possess two identical alleles for a particular gene. This condition can occur with either two dominant alleles or two recessive alleles. For example, if a gene has a dominant version represented as "A" and a recessive version represented as "a," a homozygous individual could either be "AA" (homozygous dominant) or "aa" (homozygous recessive). This genetic uniformity can have significant implications for the traits expressed in the individual, as homozygous alleles will lead to consistent phenotypic outcomes compared to heterozygous individuals, who carry two different alleles.

The other options pertain to different genetic concepts, such as heterozygosity (having two different alleles) or the absence of alleles altogether, which do not apply to the definition of homozygosity.