Summaries of Levels of Confidence and Numbers of Matings
Below are some tables that summarise the levels of confidence and numbers of matings required to detect a completely recessive allele.
These assume that all the mates are of one group, such as all are known carriers, or all are daughters, or all are randomly picked from a population.
[Tabulating confidence levels here for a mix of mates from different groups (eg where some are known carriers, some are daughters, and still others are randomly picked) isn’t practical. There are two many combinations of some number of known carriers, for some other number of daughters, for some other number again of randomly picked individuals. Formula 4a here can be used manually for any specific scenario however. (There is no formula for the reverse, determining the number of matings with mixed groups for a required level of confidence, as these cannot be easily calculated for more than one n.)]
1. Number of Matings Required to Detect a Completely Recessive Allele When Litter Size m = 1
| Genotype of Mate | [Dn] = 95% | [Dn] = 99% |
| homozygous dominant (’AA’) | infinite | infinite |
| heterozygous dominant (’Aa’) — a known carrier | 11 | 16 |
| homozygous recessive (’aa’) | 5 | 7 |
| daughter (either ‘AA’ or ‘Aa’) (assumes dam is homozygous dominant ‘AA’) |
23 | 35 |
| daughter (either ‘AA’ or ‘Aa’) of any known carrier | 23 | 35 |
| mate chosen randomly from the population (assumes 20% are carriers (’Aa’) and no homozygous recessives) |
59 | 90 |
| mate chosen randomly from the population (assumes 5% are carriers (’Aa’) and no homozygous recessives) |
239 | 367 |
2. Number of Matings Required to Detect a Completely Recessive Allele When Litter Size m = 5
| Genotype of Mate | [Dn] = 95% | [Dn] = 99% |
| homozygous dominant (’AA’) | infinite | infinite |
| heterozygous dominant (’Aa’) — a known carrier | 3 | 4 |
| homozygous recessive (’aa’) | 1 | 2 |
| daughter (either ‘AA’ or ‘Aa’) (assumes dam is homozygous dominant ‘AA’) |
7 | 10 |
| daughter (either ‘AA’ or ‘Aa’) of any known carrier | 7 | 10 |
| mate chosen randomly from the population (assumes 20% are carriers (’Aa’) and no homozygous recessives) |
19 | 28 |
| mate chosen randomly from the population (assumes 5% are carriers (’Aa’) and no homozygous recessives) |
78 | 119 |
3. Number of Matings Required to Detect a Completely Recessive Allele When Litter Size m = 10
| Genotype of Mate | [Dn] = 95% | [Dn] = 99% |
| homozygous dominant (’AA’) | infinite | infinite |
| heterozygous dominant (’Aa’) — a known carrier | 2 | 2 |
| homozygous recessive (’aa’) | 1 | 1 |
| daughter (either ‘AA’ or ‘Aa’) (assumes dam is homozygous dominant ‘AA’) |
5 | 8 |
| daughter (either ‘AA’ or ‘Aa’) of any known carrier | 5 | 8 |
| mate chosen randomly from the population (assumes 20% are carriers (’Aa’) and no homozygous recessives) |
15 | 23 |
| mate chosen randomly from the population (assumes 5% are carriers (’Aa’) and no homozygous recessives) |
62 | 96 |
These tables show very well how much the type of mate determines the number of matings that will be required for a particular level of confidence. Always choose as best you can with what you have to keep the number of matings as low as possible!
Also evident is how larger litter sizes require so fewer matings to achieve higher levels of confidence.
Always factor in more matings than your calculations would indicate, to compensate for a (likely) less than 100% successful birth rate.
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