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I love having a blackboard in my home office

In class this week we are discussing genes alleles homologous genes between species and pseudogenes. In order to organize my thoughts (to the extent that I can), I sketched out this diagram to model the flow of information from DNA into proteins and tie this together with the idea that DNA undergoes mutations from time to time and that these mutations are the source of new alleles in the population.

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 1.Recall the central dogma

DNA –> RNA –> Protein

Information flows from the DNA out of the nucleus giving rise to proteins that make up the body and do its work. For EVERY gene, you have two alleles, one from mom, one from dad. We tend to only talk about the ones that give us distinct traits that we can see from the outside, but every gene these.

2. Mutations are altered forms leading to altered function

All genes are subject to mutations. Mutations may change the protein that the gene encodes or not. In cases when it does change the protein, we may see a change in function (Form dictates Function). Once we have two different versions of a gene that remain for any period of time, we call these forms alleles of the gene.

3. Interaction of Alleles

Mutations result in these new alleles that may function differently. This may manifest in a form of dominance. If one allele codes for a protein and a second suffered a mutation such that no protein is made, we may look for the protein and say that the form that makes the protein is dominant because one copy should be sufficient to get it made.

4. How can Alleles become Pseudogenes?

Sometimes, genes mutate into a nonfunctional allele that has no impact on the organism (e.g. vitamin C synthesis is not required when the animal eats sufficient vitamin C) in this case, there will be no selective pressure against the non-functional allele resulting in more mutations occurring without consequence. Over time, these alleles can be made completely non-functional.  Pseudogenes are the remnants of these old genes that we can find in the DNA, but that are no longer functional due to an accumulation of mutations. (Only if both copies are mutated and there is no functional copy of the gene in the population do we can this a pseudogene).

5. Speciation and Relationships

As time passes, and speciation occurs, we can still see similarities between the genes of the descendent species, whether these are functional, or sometimes even when they are non-functional. My analyzing the similarities between shared genes, it is possible to infer some relationships between species and even quantitate these relationships in a way that can be used to construct a phylogenetic tree.

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Posted by on February 14, 2014 in Uncategorized

 

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You will soon witness a miracle

On friday I had lunch at Panda – something -or-other at the mall. Along with my orange chicken and spring roll I got a fortune cookie with fortune the likes of which I have never before seen: “You will soon witness a miracle.” That’s a little off-putting. I mean, miracles only seem warranted when something really bad has happened. I crossed my fingers and hoped for the best.

Then, I totally forgot about it. However, last night, I was reminded of that amazingly powerful cookie when the weatherman showed the extended forecast. Rain, cool days with high temperatures that might allow some time outside. Amazing!

I’ve made so much noise here complaining about the heat and lack of rain leading to the end of the world as I saw it that I thought it was my duty to write now.

There is a change in the air. The weathervane has spun about and a cool breeze is settling across our little patch of the midwest. Mary Poppins has floated into town with her miracle-filled carpet bag stuffed chock with cool mornings, thunderstorms and the chance of a drenching rain later in the week.

With a spoon full of sugar she is attempting to nurse our lifeless grass and trees back to health. I only hope that she has magic enough to bring back the dead (I can’t recall any resurrections in the original) But I did have a dream last night that there was a hint of green grass poking through the ground in our yard, so I have my fingers crossed.

I still have a horribly dreary outlook for the region here and all the dead trees and miserably large landscaping I am imagining, but there is light at the end of the tunnel in the form of a dark stormcloud on the horizon.

 

 

 
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Posted by on August 13, 2012 in Uncategorized

 

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