Video Transcript
What is meant by noncoding DNA? (A) DNA that has no use and it’s
only found within prokaryotic organisms. (B) DNA that does not contain
instructions for making proteins. (C) DNA that is single-stranded
rather than double-stranded. (D) DNA that can’t be extracted
from the organism. (E) DNA that is not present within
the genome.
Let’s go over what we know about
DNA. DNA, or deoxyribonucleic acid, is
the molecule that carries the genetic information in all living organisms. A molecule of DNA is most commonly
composed of two strands, each of which is a chain of individual units called
nucleotides. We can see these different
nucleotides here and the corresponding nucleotide sequence of one of these strands
as it coils around the opposing strand.
In humans, if we look at the
complete sequence of DNA, or our genome, it’s over three billion nucleotides
long. We discovered this after sequencing
the human genome during the Human Genome Project, which was a worldwide effort by
multiple scientists that took over 10 years to complete.
Besides learning about the size of
the human genome, we also discovered that our genome contains over 20,000
protein-coding genes, which represents about one percent of our genome. This includes sequences that code
for proteins, such as insulin or hemoglobin. The remaining 99 percent of our
genome is made up of noncoding DNA. This is a DNA sequence that doesn’t
code for proteins. These sequences can include
structural RNA, such as ribosomal or rRNA, or regulatory RNA molecules like
micro-RNA. However, about half of our DNA is
made up of repetitive DNA sequences with no clear function.
Going back to our question, the
option that best describes what is meant by noncoding DNA is given by answer choice
(B), DNA that does not contain instructions for making proteins.
