Discussion about gene conservation

[HydrogenBond]

Moderation note: The first 6 post of this thread were moved from the offbeat news thread 22600, because they’re not a discussion of the news article’s subject, but a more general discussion about genetics.

 

If you look at the premise that all humans evolved from the same genetic line, it says something interesting. What it says is that genetic changes are not entirely random along the DNA, or else the entire DNA would subject to constant genetic change, making it difficult to trace genetic lines. We can trace ancestry farther and farther back into time because large portions of the DNA are conserved. For example, the genes used for DNA packing proteins are very conservative.These don't change very much.

 

The question becomes how/why does life conserve genes, so we can see genetic commonality traced over long periods of time even in diverse species with environmental separation? One way is life is goal or milestone orientated. These genetic goals are conserved because they reach a milestone and don't need change. The same basic thing can form independently simply by reaching all the milestones.

Edited November 9, 2010 by CraigD
Added moderation note

[JMJones0424]

Saying large portions of a species' DNA has been conserved is not the same as saying some genes are conservative. (That being said... is there a more stringent editting mechanism for some particular genes to ensure fewer transcription errors?) Random changes that result in relatively trivial changes in morphology get passed on to offspring. Random changes that result in non-trivial, catastrophic changes cause (for example) either the failure of the fetus to develop, or the premature death of the individual before it reproduces, therefore those changes are not passed on. There is no guiding hand, and life is not goal oriented in the sense that you use. If the random change allows the individual to procreate, especially if it allows the individual to outcompete its competitors, then the change passes on. If not, then it doesn't.

[HydrogenBond]

We can define the family tree of life on earth by looking at the genetics. This is possible because basic genetic similarities are conserved. If the DNA's change was completely random, and not built upon layers, you would not be able to do this. You could not tell anything from the DNA other that it was a form a life.

 

Selective advantage sort of says the same thing, but says it more in the context of the limited number of genes that are still in flux. If we go back in time, what was once in flux, eventually becomes part of those conserved layers we wil still see in the future; once the milestone is met.

 

As an analogy, say we were building a crystal from solution. As atoms assume the lowest energy arrangement of the crystal, the entropy there becomes very limited but not necessarily zero. The main entropy is at the surface where atoms are in flux trying to find their place in the crystal.

 

When we look at the DNA, from the genes we can sort of see how the crystal formed over time by means of the genes that are conserved forward through time.

 

The question becomes how does the cell segregate the entropy on the DNA so it can conserve genes as well as keep others in flux for continued evolution toward milestones which will someday also be conserved? Then we can look at the DNA and infer the family tree of life.

[Ken]

We can define the family tree of life on earth by looking at the genetics. This is possible because basic genetic similarities are conserved. If the DNA's change was completely random, and not built upon layers, you would not be able to do this. You could not tell anything from the DNA other that it was a form a life.

 

Selective advantage sort of says the same thing, but says it more in the context of the limited number of genes that are still in flux. If we go back in time, what was once in flux, eventually becomes part of those conserved layers we wil still see in the future; once the milestone is met.

 

As an analogy, say we were building a crystal from solution. As atoms assume the lowest energy arrangement of the crystal, the entropy there becomes very limited but not necessarily zero. The main entropy is at the surface where atoms are in flux trying to find their place in the crystal.

 

When we look at the DNA, from the genes we can sort of see how the crystal formed over time by means of the genes that are conserved forward through time.

 

The question becomes how does the cell segregate the entropy on the DNA so it can conserve genes as well as keep others in flux for continued evolution toward milestones which will someday also be conserved? Then we can look at the DNA and infer the family tree of life.

 

The cell doesn't segregate the entropy on DNA. The "segregation" is solely a function of viability, i.e., certain fundamental patterns are necessary for life. Other patterns are necessary for compatibility between the embryo or fetus and the uterine environment. Still others are necessary for the viability of the organism to survive outside of the uterus.

 

I think you've gone astray by assuming that all DNA combinations are of equal "value" in maintaining life. There are huge sections of genomes that are similar or identical across vastly different species or Families or Orders because they control functions such as oxygen utilization, or internal communications, etc. These are "conserved" because when they mutate no life ensues. The further you get from basic life functions the more variation could still allow life to continue.

 

Think of life-threatening variation Vs casual and non-lethal differences between organisms. In humans hair color is a casual difference while differences in chromosome number at the 21st position is critical to competent functioning and life expectancy (Trisomy 21 aka Down syndrome).

 

Conservation of genetic coding is an observation, not a compelling force.

[HydrogenBond]

I understand the traditions, but think logically. If we took 1000 cells and randomly changed the DNA in each of the cells, we would screw up more cells than we would benefit; more things can go wrong than right. The observed level of attrition is not that high. The cell has a way to conserve many things, so the changes that do occur result in the observed low rate of attrition. I call these conserved genetics, milestones, which are taken out of the mutation loop more often than not, so change is progressive.

 

The family tree inferred from DNA implies conservation. Maybe someone can run a program that randomly changes the DNA, throughout the DNA. See how many years or generations it takes until the final DNA is not recognizable from the initial when the entire DNA is pertubated. Then run the program by conserving or restricting the changes to certain areas of the DNA we know ancient life had in common. Once you can see that then we begin to answer how life is able to segragate the DNA into conserved and flux genes.

[Ken]

I understand the traditions, but think logically. If we took 1000 cells and randomly changed the DNA in each of the cells, we would screw up more cells than we would benefit; more things can go wrong than right. The observed level of attrition is not that high. The cell has a way to conserve many things, so the changes that do occur result in the observed low rate of attrition. I call these conserved genetics, milestones, which are taken out of the mutation loop more often than not, so change is progressive.

 

The family tree inferred from DNA implies conservation. Maybe someone can run a program that randomly changes the DNA, throughout the DNA. See how many years or generations it takes until the final DNA is not recognizable from the initial when the entire DNA is pertubated. Then run the program by conserving or restricting the changes to certain areas of the DNA we know ancient life had in common. Once you can see that then we begin to answer how life is able to segragate the DNA into conserved and flux genes.

 

LIfe doesn't "segregate" DNA into conserved genes, death does. Mutations and transcription errors occur all the time, if they are in genes that have a trivial impact on life they may be "conserved" or they may not. For genes that play a critical role in sustaining life the mutated forms result in death. The death may be at the embryonic level, the fetal level, at birth, etc.

 

The same filter operates for critical genes or trivial genes - viability.