Iconic Peppered Moth - gene mutation found

Where is there any evidence that the mutation only came about when it was needed?

The only way you get dominant and recessive alleles of the same gene is through mutations. The reason that they are dominant and recessive is due to DNA sequence differences brought on by mutations.Edited by Taq, : No reason given.

It is known by observation as is being discussed in this thread. Another example is brown and black colored pocket mice:Just a moment...We have those exact observations. Of the sequence differences between these alleles, which are you saying could not be produced by the observable mechanisms of mutation?Edited by Taq, : No reason given.

Where did you show that this was the ONLY time the mutation occurred?Edited by Taq, : No reason given.

The same thing happened in pocket mice. They also evolved black coloration, and it was a dominant allele. However, the gene is strongly selected against in the normal light beige desert. Only when volcanic eruptions produced black volcanic rock was there a niche for the black mice to be selected for. What we see are islands of black mice in and around old black lava flows, surrounded by a sea of light beige mice.The interesting part is that the black allele is dominant. However, you can't find black mice at any appreciable distance away from the black lava fields, which act as islands for the black allele. They were even able to show that there is free interbreeding between the black mice and the brown mice, but the black allele still doesn't spread far from the black volcanic islands in the light brown desert. Just a moment...What is also interesting is that the black lava flows are relatively recent compared to the much older light beige desert.Edited by Taq, : No reason given.

Indeed, it is. In both situations we have a long history of strong negative selection against a dominant allele. This means that any mutations leading to dark coloration would be almost immediately eliminated from the population in past environments. Therefore, the mutations had to occur after the negative selective pressure was removed.Do you agree?Edited by Taq, : No reason given.

This is especially true of a dominant allele. Every individual carrying a single allele for dark coloration would experience negative selection. For a recessive gene, only individuals carrying two copies of the allele will experience negative selection. Recessive alleles will not be eliminated as quickly from a population, but given strong enough selective pressures they will be removed. As examples, there are many lethal recessive genetic diseases that are still circulating in the human population (e.g. Tay-Sachs disease).Edited by Taq, : No reason given.

Just as there is more than one way to skin a cat, there is more than one way to produce dark coloration. There are several different proteins and genes involved in the timing and extent of melanin production. Any one of those genes is a target for mutations that can change fur and skin coloration.The fact that you have islands of black lava each with their population of mice with unique alleles is an indication that they evolved independently of one another and did not originate from a common mutation found in an ancestral population.

First, the idea of a pre-existing dark allele is thoroughly disproven. The allele would have been removed from the population in the absence of these lava fields due to negative selection. Therefore, it had to come about through mutation after the lava fields were produced by relatively recent volcanic eruptions.Second, you haven't shown that it showed up on cue. There could have been hundreds of thousands of years between the volcanic eruptions and the occurrence of the mutation. You also haven't shown the rate at which the mutation appears in the absence of the black lava fields. What we do know is that the reason for the difference in fur color is mutations.

As shown above, that is easily done in a mouse population. Even using your number of a million births in order to get one black mouse, that is easily done with even a small population of 10,000 mice. That is just 100 generations for a species with a 3 month generation time. That would be about once every 30 years, by my calculations.