| FAQ | Why are Dominant, Overdominant, Incompletely Dominant, or Codominant Mutations Generally Heterozygous? |
| If a geneticist is continually working with his stocks, he would
immediately notice
when a new phenotype emerged due to a new mutation. A new
mutation is an extremely rare event. Probably only a few
individuals (often one) would have originally inherited that mutant allele. A
recessive mutation can "hide" in the population for many
generations since it will only occur in heterozygotes. When two
rare heterozygous individuals mate, on average 1/4 of their progeny will be
homozygous (A1A1) and show the mutant
phenotype. In organisms with very low fecundity, however, there
might be only a single mutant individual. If the new mutation is dominant or overdominant, or incompletely dominant or codominant, a new phenotype shows up heterozygous individuals (A1A2) the first generation after the mutation occurred. That is, the mutation cannot "hide". For individual with a mutant phenotype to be homozygous, the same mutation would have had to occur in both parents (very, very unlikely!!!!!) Alternatively, the geneticist would have had to have been very lax in observing his stocks and the heterozygotes would have been interbreeding for several generations without the new mutation being detected. |
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Related Tools |
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| Parental Lines | 1 |
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How to Obtain a Parental Line a) Autosomal Trait b) Sex-linked XX-XY c) sex-linked ZZ-ZW |
2 |
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How to Obtain a Parental Line for a Dominant Allele a) Autosomal Trait b) Sex-linked XX-XY c) sex-linked ZZ-ZW |
3 |
| How to Breed a Homozygous Line for more than one gene | 4 |
| F1 cross | 5 |