Question

What phenomenon explains the following data?

Virus 1 - 100 Kb genome, 99 Kb protein coding

Virus 2 - 1 Mb genome, 998 Kb protein coding

Bacterium 1 - 5 Mb genome, 4.9 Mb protein coding

Bacterium 2 - 11 Mb genome, 10.8 Mb protein coding

Plant - 5000 Mb genome, 15 Mb protein coding

Fungus - 50 Mb genome, 11 Mb protein coding

Grasshopper - 500 Mb genome, 18 Mb protein coding

Snake - 1200 Mb genome, 19 Mb protein coding

Group of answer choices

a. very high body complexity in plants

b. a strong relationship between total genome size and body complexity across all life

c. Large amounts of non-coding DNA in prokaryotes

d. a lack of a link between genome size and organismal complexity in prokaryotes and viruses

e. Large amounts of non-coding DNA in eukaryotes

Answer 1

The genome represents the genetic material (DNA) of an organism which includes all coding regions, non-coding region and mitochondrial. chloroplast DNA. Coding region are DNA sequences which code for proteins whereas non-coding region are DNA sequences which do not code for proteins. The non-coding region includes introns, and these regions can be a tandem repeat or interspersed repeats. These non-coding regions have regulatory functions. In general, prokaryotes have small, less complex DNA as compare to eukaryotes although exceptions are there as some bacteria are very large and some small size eukaryotes.

The statement (e) large amount of non-coding DNA in eukaryotes is the right answer for the given data. In eukaryotes, non-coding regions/ DNA contributes to the majority of the genome.

Plants are classified into the eukaryotic category and it does not represent all eukaryotes (grasshopper, snakes, fungi also eukaryotes) so, very high body complexity in plants is not the right answer.

A strong relationship between total genome size and body complexity across all life is not the right answer. In prokaryotes, there is a linear relationship between genome size and the number of genes but this not the case in terms of eukaryotes. In eukaryotes, genome size is not correlated with the complexity of the organisms, eg. largest genome is reported in a single cell amoeba (686,000 Mb which is 200 fold larger than human).

A large amount of non-coding DNA in prokaryotes is not the right answer because in prokaryotes non-coding region contributes less percentage of their genome as it is given in data bacterium 1 genome size is 5 MB and 4.9 MB of genome codes for protein and only 0.5 MB shares non-coding region. Similar is true in the case of bacterium 2 which is having 11 MB genome size but only 0.2 MB constitute non-coding region ( 10.8 MB codes for proteins).

A lack of a link between genome size and organismal complexity in prokaryotes and viruses is not the right answer. Prokaryotes are simple organisms compare to eukaryotes which justify their less complex genome. Viruses have either DNA or RNA as their genetic material and codes for some protein necessary for virus envelop as a virus uses host cell machinery for its duplication so there is no requirement for large or complex genome size.