Question

If two chromosomes of a species are the same length and have similar centromere placements and yet are not homologous, what is different about them?

Short answer

Answer: Two chromosomes of a species may be the same length and have similar centromere placements but not be homologous due to differences in their gene sequences and arrangements. This can be a result of chromosomal rearrangements, duplications, deletions, or inversions that occurred during evolution or as a consequence of genetic mutations.

Step-by-step solution

Understand homologous chromosomes

Homologous chromosomes are pairs of chromosomes that have the same size, shape, and gene locations (loci) but may possess different versions of those genes (alleles). In a species, homologous chromosomes are inherited from each parent – one paternal and one maternal.

Consider gene sequence and arrangement

If two chromosomes have the same length and similar centromere placements but are not homologous, their gene sequences and arrangements likely differ. Even though they may appear similar in terms of size and centromere placements, the genes present and their order on the chromosomes can be different, making them non-homologous.

Identify possible variance

Since the chromosomes in question are not homologous, it is likely that a significant difference exists in the DNA sequences or gene arrangement between them. These differences could be due to chromosomal rearrangements, duplications, deletions, or inversions that occurred during evolution or as a result of genetic mutations.

Conclusion

In conclusion, two chromosomes of a species that are the same length and have similar centromere placements but are not homologous differ in their gene sequences and arrangements. They may appear similar in size and centromere placement, but the actual genetic information contained within them is different, making them non-homologous chromosomes.