Organism's Genus and Species Estimated Size Estimated Gene Number Average Gene Density Chromosome Number

Question

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, number of genes, and number of chromosomes for a variety of different organisms. Based on what is known about the genetic code of all living things, which statement is MOST accurate concerning these organisms?
Responses
A The more complex the organism, the larger the genome.The more complex the organism, the larger the genome.
B The more complex the organism, the more complex the genetic code.The more complex the organism, the more complex the genetic code.
C Regardless of complexity, all organisms contain the same four nitrogen bases within their genetic code.Regardless of complexity, all organisms contain the same four nitrogen bases within their genetic code.
D Regardless of complexity, all organisms contain the same sequence of nitrogen bases in their genetic code.

Answer 1

The statement that is MOST accurate concerning these organisms is:

C. Regardless of complexity, all organisms contain the same four nitrogen bases within their genetic code.

This statement reflects the fundamental nature of DNA (or RNA in some viruses), where all living organisms use the same four nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G). While the size of the genome and the number of genes can vary greatly among organisms, the basic building blocks of the genetic code remain consistent across all forms of life.

The other statements (A, B, and D) are not accurate across all organisms:

• A is not always true as some simpler organisms can have large genomes.
• B incorrectly implies that complexity correlates with a more complex genetic code, which is not the case.
• D is false because different organisms have different sequences of those nitrogen bases.