As the distance between loci increases the probability of cross-over or chiasma formation during meiosis increases, so that there will once again be four phenotypes. Mutation Breeding experiments are possible because of variation at particular genetic loci. All of the variation within and between species originated in mutations of one kind or another. Most mutations are damaging or lethal and do not survive. Others may be neutral in their effects and occasionaly mutation leads to an increase in fitness.
Point mutations involve substitution of one or a few bases through replication errors.
This may lead to amino acid changes in proteins which could be neutral or silent if they are not in a critical region of an enzyme. This shows effects of different base changes in DNA on part of the amino acid sequence of a protein. Loss of one or more three-letter codons may not be so bad. Inversions of sections of DNA within a chromosome can occur by errors in ligation of broken ends during crossing over. This may have little effect on the growth of the progeny but there may be further problems during meiosis in the next generation.