Alleles,Genotypes and Phenotypes

[Poison]

to your concerns...

'One well known example of mutation is non-disjunction. Non-disjunction is when the spindle fibres fail to seperate during meiosis, resulting in gametes with one extra chromosome and other gametes lacking a chromosome.

If this non-disjunction occurs in chromosome 21 of a human egg cell, a condition called Down's syndrome occurs. This is because their cells possess 47 chromosomes as opposed to the normal chromosome compliment in humans of 46.'

here is the link:
http://www.biology-online.org/2/7_mutations.htm

[2810712]

The allele refers to the phenotype of the gene, or the trait that the gene codes for. Example, in mendels' little pea pod experiment, there were 2 genes, one for smooth seeds and one for wrinkled seeds. So there are 2 alleles here (and they are usually shown by a capital and normal letter, S for smooth, s for wrinkled).

Genes become mutated.
I am explaining my q. here-
There may be two or more forms of a gene i.e. two or more different DNA sequences
. So, mutation may occur in any one of them . Let A & B be two diff. DNA sequences of a gene . If mutation occurs in A as well as in B , the two mutations are different in the sense they have different raw materials. so, we can't simply group them under " the mutations in the gene of some trait " Thus the " the mutations in the gene of some trait "
can be classified on the basis of raw materials [ the forms of a gene in which they have occured ] , so, the forms of genes are mutated . & what will you call the different forms of a gene i.e. different DNA sequences ? As per I know[b] [b]they R nothing but alleles !!!!
Alleles are not phenotypes .[/b][/b]

hrushikesh