Final answer:
The correct description for the arrangement of genes on each pair of homologous chromosomes is that while the alleles may vary, the genes are in the same order. Alleles represent different versions of a gene, and their combination, either identical or different, determines an individual's traits. Recombination during meiosis can shuffle alleles but does not alter the linear order of genes.
Step-by-step explanation:
The correct answer to the question of how genes are arranged on each pair of chromosomes is D. The alleles can be different; the genes are in the same order.
Homologous chromosomes contain the same genes in the same linear order, which allows for the traits they code for, such as 'hair color,' to be inherited consistently. However, because each chromosome in the pair comes from a different parent, the alleles (different versions of the same gene) may vary. This variation can result in different traits being expressed by the offspring. For example, with the blood type gene, a person may inherit two identical alleles (like AA or OO), or two different alleles (such as AO or AB), which can lead to different blood types. During meiosis, particularly in the process of recombination, alleles may be shuffled across the chromosome without altering the gene order. This exchange of genetic material can introduce new combinations of alleles into a population.
It is important to note that while alleles can be shuffled and assorted independently due to crossing over and independent assortment, the genes themselves remain in the same sequence on each chromosome. This consistency is crucial for the correct function and expression of genetic traits.