Video Transcript
What is the correlation between the
complexity of an organism and the number of protein-coding genes it contains?
Before we answer this question,
let’s look at a few key terms. A gene is a section of DNA that
produces a functional unit. So if we had a section of DNA with
two genes on it, one of them might produce a protein — like insulin, for example,
that’s involved in regulating blood sugar levels — or a functional RNA molecule,
like a special type of RNA called microRNA that’s involved in regulating gene
expression. So there’re really two types of
genes. Protein-coding genes code for
proteins, while genes that don’t code for proteins but instead produce an RNA
molecule’s function are called noncoding genes.
The genome is the complete set of
genetic material of an organism.
And by studying the genomes of
different organisms, for example, the protozoan
Trichomonas vaginalis
, the
fruit fly, and a human, we’ve determined the number of protein-coding genes that the
organism contains.
Trichomonas vaginalis
has
about 60,000 protein-coding genes, the fruit fly has about 14,000, and humans have
somewhere between 20 and 25,000 protein-coding genes.
Since this question is asking us
about the complexity of organisms relative to the number of protein-coding genes,
let’s rank them. We can say that Trichomonas
vaginalis is the least complex because it’s only a single cell, whereas humans are
the most complex because they’re multicellular, have more tissue types and a more
advanced nervous system than our fruit fly. So our relative complexity can look
something like this. This question is asking us about
the correlation, or relationship, between the complexity of an organism and the
number of protein-coding genes it contains. So as complexity increases, what
can we say about the number of protein-coding genes?
Well, if we look at the fruit fly
and the human, we can see that as complexity increases, so do the number of
protein-coding genes. But if we look at Trichomonas
vaginalis and the fruit fly, we see that the opposite is true. And as complexity increases, the
number of protein-coding genes decrease. So we see no consistent
relationship between organisms, which means there is no correlation between
complexity and the number of protein-coding genes.
