-These are the challenges faced with genes in 2001.
-When they sequenced the genome, they started to try and figure out
where the genes were. They didn’t know all of the genes, they knew
about 50% of the genes, but they didn’t know all of them and this was
one of the key things: to identify where the genes were and what they
-Why do we care so much about genes? Over the last 100 years, people
realized that genes are absolutely critical for understanding the
phenotype of an organism.
-Let’s take a look at how the definition of genes has evolved over the
last 100 years.
-In the 1900s, the term gene was only known as a theoretical thing. It
was known that there were these traits, they called them genes but they
didn’t have any idea what they were. All they knew was you could have
a change in the gene and it would cause a different phenotype. So the
idea of the gene was in place b/c you could examine what a plant looked
like & see that it was short or tall & you could transmit that info to
offspring so they knew that there was a physical gene but they didn’t
have any sense of what it really was.
-In 1950-1960’s, with the info from Oswald Avery’s experiments, the
scientists realized that the genes were DNA. Initially, they just thought
that the idea was that there was DNA and it coded for RNA so that
knowledge came about with experiments done in the 50s and 60s.
-In the pictures, each triangle is supposed to represent a change. So it
was known that if there was a mutation or a change in the DNA
sequence then you could have a change in the phenotype. For example,
blue flowers or red flowers; a bacterium that is virulent and one that is
not; a change in the gene here that could cause the death of a mouse.
-Within the 1970s and up to the 2000s, people realized that the protein
coding info of a gene is not continuous but is split up by these intron
sequences. So there are both intron sequences and protein coding
regions. And that the initial transcript of RNA is spliced to form a
mature messenger RNA and that’s what allows us to have different
isoforms of proteins. This is probably the definition of a gene that most
of us are familiar with: the idea of the DNA being transcribed and RNA
being processed and translated.
-Early on, in the 1970s and 1980s and even to the 1990s, the rest of the
DNA was considered to be spacing – it was considered to be junk & not
really carrying any info. The idea was that the protein coding regions
(only about 3% of the genome) & the rest just happened to be repetitive
DNA or not useful info. This idea has changed & now we know that this