Mating systems Flashcards
animal breeding scheme goal
=animal improvement
=genetic improvement
animal breeding scheme
-selection method (whose records)
-selection techniques (how & what)
-mating systems
mating systems
within breed:
-inbreeding
-linebreding
-outcrossing
-random mating
across breeds:
-crossbreding
-grading up
-synthetic production
inbreeding
-used in:
-purebreds:
-race horses
-show dogs
-poultry (to produce lines which are then crossed)
-point: increase homozy loci
-mating of “close relatives”
(brother x sister), (2nd cousin x 2nd cousin)
linebreding
-from of inbreeding where a prominent relative is re-introduced
what does inbreeding increase
-homozygosity
-exposes recessives
-(undesirable, lethal, but also desirable)
where was inbreeding seen historically
-royalty:
-tutankhamun
-hapsberg jaw
-hemophilia
where is inbreeding still practiced today
-middle east, central south asia, and the americans
-arranged marrages with first cousins
-grandfather marries granddaughter
Hutterite, amish-few founding members
for inbreding to work:
a) cull heavily
or
b) be very homozygous already
different types of relatives
-direct
(in the line of decent “directly” e.g grandmother)
-collateral (common ancestor/s but not in direct line e.g. cousin)
-can have direct & collateral simultaneously (occurs only in inbreeding)
what does inbreeding expose
deleterious recessive
what is the inbreeding coefficent
F
quantitative level of inbreeding
-F= inbreeding coefficient
-fraction of loci an individual has with 2 alleles, inherited from a common ancestor
-chance of homozygosity of a rare mutant allele (inherited form an ancestor through both sides of the pedigree)
where must ancestors appear on the pedigree to contribute to inbreeding
on both sides
inbreeding co efficient values
-no max
->0.25 is high
-compounded by several relative
what is the appx inbreeding coefficent for humans, hutterites and second cousins
~.001 for western society
~.05 for hutterites
~.016 for second cousins
what traits are ill affected by inbreeding
-traits of low heritability, particularly fertility. & hardiness are ill affected by inbreeding
impacts of inbreeding in beef cattle
-weaning wt
(dec about .3kg for each 1% of inbreeding of calf, additional .25-.50kg for each 1% inbreeding of dam)
-fertility and calf viability
(10% increase in inbreeding of dam, =2% increase on non preg cows, 1% reduction in calves weaned/pregnant cows)
how to avoid inbreeding in beef cattle
new bull/s every 3 years
yr 1-mates unrelated cows
yr 2-calves born, remate coes
yr3-heifer daughter separated, mates with cows again
why inbreed
1) develop new breed or line
-mutant color
2) maintain rare breed
-no alternative
-zoo animals
3) recreate a prized individual
(linebreed)
-race horses
4) develop lines for crossing
-company boiler chicken
5) highly inbred research animals
6) detect recessives the breed carries
-cull to “clean up”
out crossing
mating animals within the same breed that are not related
-how far back? 4-6 generations
random breeding
-draw mates at random
-corral together and let them decide
why random breeding
-to maintain gene pool
-zoo animals
-rare domestic breeds
crossbreeding
-mating animals pf 2 different breeds
-heterosis (hybrid vigor)
-breed complementary
-individual heterosis
