Question

Humans have an estimated 24,000 protein-coding genes in their genome, whereas Arabidopsis, a small plant, has 28,000 genes. Which statement best describes how the number of genes relates to the complexity of the organism?

A. Organisms that are more complex always have more genes.

B. Organisms with more genes are always less complex.

C. There is no relationship between organismal complexity and number of genes.

D. A higher number of genes generally correlates with complexity, with exceptions.

Answer 1

The relationship between gene count and organism complexity is not direct; humans have similar gene numbers to less complex organisms but can produce many proteins from a single gene due to processes like splicing.

Step-by-step explanation:

The number of genes is not directly proportional to the complexity of an organism. Humans have an estimated 20,000 to 25,000 genes, which may seem like a large number, but other less complex organisms have a similar number of genes. However, what sets humans apart is how their cells can use splicing and other processes to produce multiple proteins from a single gene, enabling a vast array of protein expression despite a limited number of genes.

Additionally, while each of the 23 pairs of human chromosomes carries thousands of genes, many of them do not code for proteins, and the exact function of these non-coding sequences is often unclear. The human genome is much more than just its genes; it involves complex regulation and expression patterns, demonstrating that the relation between gene count and organism complexity is not straightforward. Thus, the most accurate statement regarding the relationship between an organism's complexity and its number of genes would be that a higher number of genes generally correlates with complexity, but there are exceptions.