Mutations and Evolution?

Question

Are Mutations recessive or dominant alleles?
What exactly is 'Micro-Evolution'?
What exactly is 'Macro-Evolution'?

Thanks guys and gals.

Answer 1

A mutation might be either recessive or dominant. Keep in mind that GENES MAKE PROTEINS. So if having a protein around causes a trait, then a mutation which causes that trait will be dominant, since one copy causes the protein to be there. If only NOT having a protein around causes a trait, then a mutation which breaks an existing protein will be recessive, since everyone has two copies of each gene.

Huntington's disease is dominant. It produces an altered protein that kills off nerve cells. You only need one 'bad' copy to start producing these naughty proteins. Cystic fibrosis is recessive. The affected protein normally makes a cell membrane protein, so someone with one 'bad' gene still has that protein... just less of them. This is also why there are more than a hundred versions of cystic fibrosis - in a long gene there's lots of different mutations that will make it not work!

Micro-evolution is indisputable fact. It takes the form of changes to a 'race' of creatures that may cause huge physical differences, but not actual speciation. Examples of this include intentional breeding which produces the many, many varieties of dogs and cats and horses (and so on!) that we have around today and antibiotic-resistant bacteria that have come to dominate non-resistant breeds in some cases. Some of these changes are drastic enough that populations are effectively isolated (it's hard to imagine a St Bernard and a Chihuahua mating naturally... at least not without a lot of lubricant) even if scientific intervention can still combine sperm and egg in a viable manner.

Macro-evolution has plenty of evidence, but has arguably never been actually observed. It covers much larger-scale events which may take millions of years which cause not only speciation, but the vast diversity of all life on Earth. In many senses, macro-evolution is just a greater and greater accumulation of the same kinds of changes that produce micro-evolution... the main reason why these two kinds are distinguished is that no reasonable person disputes the first kind.

Hope that helps!

Answer 2

Loss-of-function mutations are the result of gene product having less or no function. When the allele has a complete loss of function (null allele) it is often called an amorphic mutation. Phenotypes associated with such mutations are most often recessive.

Gain-of-function mutations change the gene product such that it gains a new and abnormal function. These mutations usually have dominant phenotypes. Often called a neomorphic mutation.

Dominant negative mutations (also called antimorphic mutations) have an altered gene product that acts antagonistically to the wild-type allele. These mutations usually result in an altered molecular function (often inactive) and are characterised by a dominant or semi-dominant phenotype.

Lethal mutations are mutations that lead to a phenotype incapable of effective reproduction.

Microevolution is changes in the gene pool of a population over time that result in changes to the varieties of individuals in a population. Examples of microevolution include bacteria that have become unaffected by antibiotics, or a change in a species' coloring or size.These changes may be due to several processes: mutation, natural selection, gene flow, genetic drift and nonrandom mating.

Macroevolution can be defined simply as evolution above the species level, and its subject matter includes the origins and fates of major novelties such as tetrapod limbs and insect wings, the waxing and waning of multi-species lineages over long time-scales, and the impact of continental drift and other physical processes on the evolutionary process. Any changes that occur at higher levels, such as the evolution of new families, phyla or genera, are also therefore macroevolution, but the term is not restricted to those higher levels. It often also means long-term trends or biases in evolution of higher taxonomic levels.

Answer 3

Alien 51, this is a tricky one because it asks a question about something which may or may not even exist !

Micro-evolution refers to small changes in evolution and the classic example is the one Darwin used in reference to a bird called a FINCH.

What he said was that finches produce finches who produce finches generation after generation, all of them about the same.

BUT when food supplies changed and finches were threatened with extinction, gradually a few finches survived with little longer beaks(capable of reaching down under the bark or into holes and getting food) and the ones that survived even better were the ones that had curved beaks so that in the end Darwin found finches with LONG CURVED beaks, showing how they evolved slightly. But is this evolution or merely ADAPTATION?

This sort of science was readily accepted. What still remained in question, however was how fish became amphibians. Fossils of ancient amphibians had small legs that allowed them to climb out of the sea and on to land. but NOBODY has ever found fossils of the TRANSITIONAL CREATURES. Fossils were either fish or they were amphibians, nothing in between.

And that has been the biggest unanswerable question for scientists and creationists to tussle with.

Even in humans it is easy to find micro-evolution. We have fossils of humans (australpethicus) who were not able to talk since there was NO hyloid bone development and the throat was not forward enough to permit diistinct articulation. Later humans (homo sapiens) did have that bone development and faculty so that micro evolution seems to have occured. The big problem is the time element. Changes such as this can only be measured in millions of years.

Human beings 100,000 years ago were absolutely no different than to-day. In fact scholars now find that the human brain size today may even be slightly smaller than 100,000 years ago.
Our progress has only been in how we developed that brain and how society has indeed shaped our behaviour.