gene mutation

[vinaya]

hi all
this is my first genetics question. im really interested in it & my bio lesson is based on it.right, now to the question
what is mutation of genes? is it desirable ?

[Morris]

Mutation is a change gene sequence: it can involve a single letter, or a gene region; mutantions are caused by some factors as replication errors, DNA damages.... but some are spontaneous.
Mutations are desiderable only for evolution and only if they aren't dangerous for organism, because there are letal and harmful mutations too, that are not desiderable.

[sdekivit]

i'll mention an example for both:

gene mutation as a bad happening: mutation in tumor oncogenes causes cancer.

gene mutation as a good happening: a mutation causing sicle cell anemia also causes resistance agains malaria.

[MrMistery]

Actually i don't know how good an example is sickle cell anemia in malaria affected deseases, because it is inherited from your parents, it's not something that happens to each individual...
Here is another way of thinking about this: the mutations that happened in early human development from apes causing us to have a better developped brain were desirable becuase humans could think their way out of trouble, invent thing etc if they had a bigger brain and therefor gave us more chances to live and reproduce. As a consequence, they were kept in the genotype. Harmful mutations decrease the individual's chances to live and/or reproduce and as a consequence they are faster or slower eliminated from the genotype. Needless to say, letal mutations are eliminated, since dead organisms do not reproduce
Hope this is of some help...

[sdekivit]

it's only to show that a mution of 1 amino acid that cause sickle cell anemia the people are ressitan to malaria. That it's inherited, i don't care right now. It's only to show that this mutation also has a benefit.

[lara]

Inversion of Genes

The connection between genes break and the sequence of these genes are reversed
The new sequence may not be viable to produce an organism, depending on which genes are reversed. Advantageous characteristics from this mutation are also possible
Translocation of Genes
This is where information from one of two homologous chromosomes breaks and binds to the other. Usually this sort of mutation is Translocation of genes has resulted in some genes from one of the chromosomes attaching to the opposing chromosome
Alteration of a DNA Sequence
The previous examples of mutation have investigated changes at the chromosome level. The sequence of nucleotides on a DNA sequence are also susceptible to mutation.

Deletion
Here, certain nucleotides are deleted, which affects the coding of proteins that use this DNA sequence. If for example, a gene coded for alanine, with a genetic sequence of C-G-G, and the cytosine nucleotide was deleted, then the alanine amino acid would not be able to be created, and any other amino acids that are supposed to be coded from this DNA sequence will also be unable to be produced because each successive nucleotide after the deleted nucleotide will be out of place.
Insertion
Similar to the effects of deletion, where a nucleotide is inserted into a genetic sequence and therefore alters the chain thereafter. This alteration of a nucleotide sequence is known as frameshift
Inversion
Where a particular nucleotide sequence is reversed, and is not as serious as the above mutations. This is because the nucleotides that have been reversed in order only affect a small portion of the sequence at large
Substitution
A certain nucleotide is replaced with another, which will affect any amino acid to be synthesised from this sequence due to this change. If the gene is essential, i.e. for the coding of haemoglobin then the effects are serious, and organisms in this instance suffer from a condition called sickle cell anaemia.
All of the genetic mutations looked at through the last 2 pages more or less have a negative impact and are undesired, however, in some cases they can prove advantageous.

Genetic mutations increase genetic diversity and therefore have an important part to play. They are also the reason many people inherit diseases.