Study of genetic correlations under full -SIB mating system (Two loci case)
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Date
1985
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Department of Statistics, College of veterinary and animal sciences Mannuthy, Thrissur
Abstract
A purely theoretical investigation entitled ,JA Study
of Genetic Correlations under Fu ll-s ib Mating System (two
lo c i case)*1 was carried out with the following objectives,
i ) to derive the joint distribution (correlation table)
and to find the correlation between fu ll -s ib pairs under
fu l l -s ib mating system in the case of two lo c i when there
i s no linkage as well as when there i s complete linkage.
l i ) to derive the joint distribution (correlation
table) and to find the correlation between parent-offspring
pair© under fu l l -s ib mating system in the case of two loci
when there is no linkage as well as when there is complete
linkage,
i i i ) to derive the joint distribution (correlation
table) and to find the correlation between fu l l -s ib pairs
under paront-offspring mating system in the case of two
lo c i when there is no linkage as well as when there is
complete linkage,
iv) to derive the joint distribution (correlation
table) and to find the correlation between parent-offspring
pairs under parent-offspring mating system in the case of
two lo c i when there is no linkage as well as when there is
complete linkage.
2
Th© joint distributions of fu ll -s ib pairs and parent-
©Ffspring pairs undor fu ll-s ib gating system wore derived
with the help of generation matrix technique and th© correlations
wore worked out therefrom, assuming additive genie
e ffec ts and using the product-momeni correlation coefficient
formula. The correlations were worked out for tho f i r s t ten
generations of fu ll -s ib mating in both cases of no linkage
and complete linkage,
& comparative study of fu ll -s ib correlations and
parent-offspring correlationsf conducted both numerically
and graphically, revealed that £i) evonthough fu ll -s ib correlation
was greater than parent-offspring correlation in
in i t ia l generation (random mating) when there was complete
linkage, the la tte r increased more rapidly than the former
from in it ia l generation to f ir s t generation and ( i i ) from
the second generation onwards, the rate of increase in both
o f correlations were nearly the same upto tenth generation.
I t was interesting to note that the parent-offspring correlations
wore of comparatively higher order than th© fu ll-s ib
correlations in both cases of complete linkage and no linkage.
Similarly, th© joint distributions (correlation tables)
for fu ll-s ib pairs and parent-offspring pairs under parentoffspring
mating system were derived employing generation
matrix approach and the correlations for the f i r s t ten
3
generations of parent—offspring mating in both cases of
no linkage and complete linkage were worked out therefrom.
A comparative study of those correlations was carried out
both numerically and graphically. It was found that the
trend in both correlation curves remain the same, but the
value of parent-offspring correlation was always greater
than that of full-sib correlation in case of no linkage
as well as in caso of complete linkage.
In comparison of all these correlations, it was found
that the correlations increased as the number of generation
increased and ultimately reached the limit unity when the
number of generations increased indefinitely large. It was
also observed that the magnitude of correlation in case of
complete linkage was more than that of correlation In case
of no linkage even under the same system of mating*
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Citation
T-382