Genome Size Chart

Question

Organism's Genus and Species Estimated Size Estimated Gene Number Average Gene Density Chromosome Number
Homo sapiens (human) 2,900 million bases ~30,000 1 gene per 100,000 bases 46
Rattus novegicus (rat) 2,750 million bases ~30,000 1 gene per 100,000 bases 42
Mus musculus (mouse) 2,500 million bases ~30,000 1 gene per 100,000 bases 40
Drosophila melanogaster (fruit fly) 180 million bases 13,600 1 gene per 9,000 bases 8
Arabidopsis thaliana (plant) 125 million bases 25,500 1 gene per 4,000 bases 10
Caenorhabditis elegans (roundworm) 97 million bases 19,100 1 gene per 5,000 bases 12
Saccharomyces cerevisiae (yeast) 12 million bases 6,300 1 gene per 2,000 bases 32
Escherichia coli (bacteria) 4.7 million bases 3,200 1 gene per 1,400 bases 1
H. influenzae (bacteria) 1.8 million bases 1,700 1 gene per 1,000 bases 1

The table shows the relative size of the genomes (total DNA in the nucleus), number of genes, and number of chromosomes for a variety of different organisms. What is the relationship between the complexity of an organism and the number of chromosomes that it has?
Responses
A There is a strong tendency for advanced organisms to have more chromosomes.There is a strong tendency for advanced organisms to have more chromosomes.
B There is a strong tendency for advanced organisms to have fewer chromosomes.There is a strong tendency for advanced organisms to have fewer chromosomes.
C There is no relationship at all between the complexity of an organism and the number of chromosomes.There is no relationship at all between the complexity of an organism and the number of chromosomes.
D There is a weak link between advanced organisms and more chromosomes, but some organisms do not follow this rule.

Answer 1

The correct response is:

D There is a weak link between advanced organisms and more chromosomes, but some organisms do not follow this rule.

The data presented show that while more complex organisms (like humans, rats, and mice) tend to have a higher number of chromosomes, this isn't a strict rule. For instance, simpler organisms like Drosophila melanogaster and Arabidopsis thaliana also have a significant number of chromosomes relative to their complexity. This indicates that while there may be a tendency for more complex organisms to have more chromosomes, there are exceptions to this pattern.