Video Transcript
The Human Genome Project’s aim is
to identify all the genes in the human genome. Which of the following best
describes the difference between a gene and a genome? (A) A gene is a section of DNA that
codes for a particular protein or functional unit, whereas a genome is all of the
genetic material found within a cell or organism. (B) A genome is a section of DNA
that codes for a particular protein or functional unit, whereas a gene is all of the
genetic material found within a cell or organism.
This question is asking us the
difference between a gene and a genome. To answer this, let’s first review
how DNA is organized inside our cells. You’ll recall that our DNA is
located within the nucleus of our cells. There’s a lot of DNA stuffed inside
this nucleus. In fact, if you were to take out
the DNA from a single cell and stretch it out, it would be about two meters in
length. All of the genetic material inside
our cells, and in us in general, is what we call our genome. All of this DNA isn’t one long
continuous molecule of DNA. Instead, it’s organized into
structures called chromosomes. In humans, we have 23 pairs or 46
chromosomes in total.
Let’s take a closer look at one of
these chromosomes so we can describe what a gene is.
Our DNA is wrapped up tightly
around special proteins called histones to form a structure called a nucleosome. These nucleosomes are coiled up and
compacted further to form chromatin, which then condenses to form the chromosome
structure we see here. This extensive packaging is how so
much DNA can fit inside our cells. Throughout our DNA are genes. These are lengths of DNA that
provide the instructions for different functional units, for instance, for a protein
like insulin or hemoglobin. Our genome contains a lot of DNA
and a lot of genes. There’s about three billion
nucleotides of DNA and over 20,000 genes in our genome.
Going back to our question, the
option that best describes the difference between a gene and a genome is given by
answer choice (A). A gene is a section of DNA that
codes for a particular protein or functional unit, whereas a genome is all of the
genetic material found within a cell or organism.
