strictest definition of allele...

[imapremed]

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so an allele is any genetic differention between two dna parts right... so say we have aagttc and the same antisense strand on the anologous chromosome is aagtta, but because of the wobble effect (degenercy) it ends up coding for the same protein and thus the same allele type (not in terms of heterozygous and homozygous) but in terms of an contributed aagttc or aagtta in say a pedigree cross will end up having the same effect lets say P (big P the dominant trait)...

now are those two dna segments alleles by the strictest defintion still or are they the same thing, because they give the same big P.

this is what wiki says but im not completely sure if its saying the same thing i am thinking as above:

An allele (UK /ˈæliːl/ or US /əˈliːl/) is one of two or more forms of a gene.[1][2] Sometimes, different alleles can result in different traits, such as color. Other times, different alleles will have the same result in the expression of a gene.

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second question(S):
evolution is change in allele frequency ONLY right - like no evolution would occur if just genotype frequencies were changing? is there a disctinction between micro and macro evolution (like micro has to have both allele and gene freq stay same) and for macro its just allele frequency.

HW requires that BOTH allele and genotype frequencies stay same? HW follows microevolution?

AND, lastly, is it ever possibly to have same genotype frequencies but different allele frequencies? i know that you can have same allele frequencies but different genotype depending on parents being hetero or homo.

 

[plzNOCarribbean]

Allele are different form of a gene. For instance, for a hair color gene, the different allele are the brown hair allele, red hair allele, black hair allele, blonde hair allele, ...etc.

so an allele, just as it sounds, are all the different forms of the gene within the gene pool. Each individual has 2 alleles for each gene, 1 which they got from their mother and 1 from father, and they only pass one of these allele to their offspring, since, due to the law of segregation, each gamete will contain 1 allele after homologs separate during meiosis 1.

 

[deleted329605]

I don't think its necessarily right saying each individuals have two alleles, because that would imply that every individual is heterozygous. I mean I guess technically at the genetic level, the probability of inheriting 2 alleles of the exact same sequence is low, so you could say that every individual is hetero at the genetic level, but once you move to phenotype level saying each individual has 2 alleles of a gene implies heterozygous which is not necessarily correct. Probably a better way to say it is that we inherit one set of chromosome (one version of each loci) from each of our parents.

In terms of allele, its probably best to look past the genetic level and into the phenotypical level where actual function arises. This can be at the cellular level like the structure of a protein or a more general anatomical/physiological trait. The genetic levels leaves the door open for a potentially infinite amount of alleles if your going to define it by the dna sequence.

 

[km1865]

you might find these two links helpful:

http://www.differencebetween.net/science/difference-between-gene-and-allele/
and
http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_42

 

[MD Odyssey]

In terms of allele, its probably best to look past the genetic level and into the phenotypical level where actual function arises.

I personally tend to disagree with this, since phenotype expression is much more complex than a simple matter of which two alleles a person has. Two people can have exactly the same genotype but express a different phenotype (e.g., hereditary breast cancer is a good example of this).

Since there are so many things which influence phenotype, beyond the alleles a person has, it seems simplest to define alleles as two different variants of the same gene.

 

[MD Odyssey]

I don't think its necessarily right saying each individuals have two alleles, because that would imply that every individual is heterozygous.

Actually, the vast majority of the entire human genome is conserved.

 

[whiteshadodw]

the strictest definition of an allele is simply a version of a gene. in terms of cooking, the allele is like a recipe. the phenotype is like the final dish. you can go to any pizza hut in the nation, and get the same pizza cuz its all the same recipe. want dominoes (different phenotype)? they use a different recipe (allele). that's not the best analogy, because when you look at it from a very close perspective, there are SNPs, where a nucleotide changes and it might not alter the function of a gene despite change an AA or it might not alter expression of a gene, or it might not change the phenotype.

not all individuals are homo or heterozygous for a particular gene. think about sex-linked genes. males are hemizygous recessive or dominant, they don't have another allele.

 

[deleted329605]

Actually, the vast majority of the entire human genome is conserved.

That's true, but conserved doesn't necessarily mean identical. Comparing the genomes of a new born child against those of the parents will show that there are an incredible number of nucleotides that have been change due mistakes made by the DNA polymerase enzyme. Heck if you compare two cells within one person's body there would probably be a large number of nucleotide substitutions. But even though the copies copies of whatever gene you are looking at aren't identical due to random mutations (we are assuming these mutations aren't lethal) it doesn't necessarily mean that the individual is heterozygous.
I was just saying above that if you are going to define alleles at the genetic level to the point where you are characterizing difference sequences of DNA as different alleles (like wobbles) it isn't a faithful indicator of the relative similarity between those two variants. Thus you want to look to the phenotype, either being the protein it codes for or the gross anatomy/physiology that the protein gives rise to.

 

[whiteshadodw]

That's true, but conserved doesn't necessarily mean identical. Comparing the genomes of a new born child against those of the parents will show that there are an incredible number of nucleotides that have been change due mistakes made by the DNA polymerase enzyme. Heck if you compare two cells within one person's body there would probably be a large number of nucleotide substitutions. But even though the copies copies of whatever gene you are looking at aren't identical due to random mutations (we are assuming these mutations aren't lethal) it doesn't necessarily mean that the individual is heterozygous.
I was just saying above that if you are going to define alleles at the genetic level to the point where you are characterizing difference sequences of DNA as different alleles (like wobbles) it isn't a faithful indicator of the relative similarity between those two variants. Thus you want to look to the phenotype, either being the protein it codes for or the gross anatomy/physiology that the protein gives rise to.

i catch your drift, and i have to agree with you considering that you sometimes have to make a simplification to make things easier. for example, there are probably tons of different ways to code for adult hemoglobin, but there is probably going to be 99% sequence identity (both aa and DNA probably) between any different versions. as long as you don't have the recessive sickle-cell anemia allele, you're good to go (yes, i'm aware that there are other polymorphisms of Hb, but just consider adult Hb and sickle cell Hb). overall, for the majority of the MCAT its probably worth it to make the allele A gives ______ phenotype, and homozygous recessive gives ______ phenotype. then there is codominance, and blah blah blah, but let's not get into that.