Define homologous chromosomes.

Homologous chromosomes are defined as pairs of chromosomes that have the same genes at the same loci but may carry different alleles. Each parent contributes one chromosome of a homologous pair. This means that while the chromosomes in a homologous pair are similar in size, shape, and genetic content, they can contain variations in their genetic sequence, which gives rise to different traits.

For example, if one chromosome carries an allele for brown eye color and its homolog carries an allele for blue eye color, these chromosomes are still considered homologous because they contain the same genes related to eye color but differ in their specific forms (alleles). This genetic variety is essential for processes such as meiosis, where homologous chromosomes can exchange genetic material, leading to genetic diversity in offspring.

The other options do not accurately describe homologous chromosomes: identical genes would imply no variation in alleles; identical copies refer to sister chromatids, not homologous chromosomes; and non-matching chromosomes from different species do not fall under the definition of homologous chromosomes, as homologs need to be from the same species and share the same genetic loci.