Class Notes (806,817)
Canada (492,453)
HMB265H1 (242)

Lec 3 - Genes and Gene Regulation

11 Pages
Unlock Document

University of Toronto St. George
Human Biology
Michelle French

Tuesday, January 13, 2009 -Todays class is on genes and gene expression. -Theres three main components: -1) Talking about what a gene is over time and how it has evolved. -2) Talking about regulation of genes and how genes are expressed. -3) Talking about how genes are identified. -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 didnt know all of the genes, they knew about 50% of the genes, but they didnt know all of them and this was one of the key things: to identify where the genes were and what they were. -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. -Lets 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 didnt 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 bc 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 didnt have any sense of what it really was. -In 1950-1960s, with the info from Oswald Averys 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 thats 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 www.notesolution.comis wrong. -If youre looking for genes in the entire genome sequence, then the knowledge of how genes are organized & regulated will help you to identify genes when you have all of these thousands & millions of base pair info. -Genes are so important because through the expression of a gene, through transcribing it and, in most cases, translating it, we determine the phenotype of us as individuals and of all the cells in the body. -The genes we know are critical for determining the phenotype. -Cells are different so in each cell, not all of the genes are expressed at the same time even though each cell has a complete copy of the genome. -Genes that are in your genome of all cells have a differential expression so brain cells will express a certain subset of genes & liver cells will express a different subset of genes. You can analyze that at the protein level which is what we see in the picture, that there are differences in the proteome of both cell types. That kind of regulation happens at 2 levels: -In the long term, when certain genes in the brain will be shut down, liver genes for example, and will never be expressed again. -Or, in the short term, when, for example, in the liver when youve eaten a meal & you need to make the enzymes to store glucose into glycogen. -So there will be times when youll need short term regulation and, on top of that, long term regulation is imposed. So short term, genes are quickly turned on and off whereas in long term, it allows for a cell to take on a certain phenotype which is the identity of it. -So what proteins you end up with in the cell can be influenced by all these steps but one of the main ones is at the level of transcription, is the gene transcribed or not? -Review the next two slides by yourself since we (Campbell and French) assume youve already learned this stuff in other courses.
More Less

Related notes for HMB265H1

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.