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sheep quiz three
Terms in this set (30)
whats a popular hair sheep developed in the u.s.
inbreeding in a seed stock sheep flock is used for one primary reason. whats that reason
to increase the frequencey of desirable traits
what would be a possible negative impact of too much inbreeding in a sheep program
inadvertent selection of undesirable traits (inbreeding depression)
why would sheep producers utilize outcrossing as a part of their sheep breeding program?
to maximize hybrid vigor
when selecting breeding sheep, will you make faster genetics progress if one trait only is being selected for or if several traits are being selected for at one-time
whats the primary reason for using terminal crossbreeding system in a commercial operation
to maximize growth and muscling for the lambs
what would be an example of quantitative traits? whys it so difficult when selecting for a quantitative trait to make significant changes or progress in a flock or herd
theres mulitple genes involved
crossbreeding often used by sheep producers as part of genetic management program. why would a sheep producer want to use any crossbreeding or breed mixing program in sheep flock
to produce lambs with favorable traits from each breed used and combine for one set of offspring
why have we seen an increase in popularity of hair type sheep breeds as commercial ewes in eastern half of the US?
low input ( labor, feed, etc)
inbreeding is a seed stock sheep flock is used for one primary reason. What is that reason?
Improve consistency, predictability and enhance desirable traits
what would be a possible negative aspect of too much inbreeding in a sheep production?
inbreeding depression and getting undesirable traits.
how would you go about selecting a group of Rambouillet ewes to be bred to a polled ram so that you would have 100% Rambouillet ram?
why would sheep producers utilize outcrossing as part of their purebred sheep breeding program?
to increase heterosis in the breed
hairy lamb syndrome is a lethal genetic disease found in the southdown breed. how does a lethal genetic disease like hairy lamb syndrome develop into a widespread genetic disorder within a population
one ram is used and is inbred to an extent that causes a gene to mutate and is then passed down to its offspring, carrying the disease
what is the most popular of the meat breeds
what 3 breeds would you use if you were charged with developing a group of commercial ewes that are prolific, can breed out of season, good moms/ milkers, durable and hardy, with acceptable wool quality and carcass characteristics
Finnish landare, polled Dorset, and Rambouillet
you dna tested for the spider lamb disease in your newest crop of lambs and thee report from the lab identified several of thee lambs as carriers. explain whats meant by this term "carrier". whats thee likelihood that an offspring is a carrier if both parents are also carriers.
carrier means that the lamb does not have the disease but carries the gene of the disease and can pass it on to their offsprings if the other parent is a carrier. 50% of being carrier
both horned Dorset and horned Rambouillet breeds have horns. briefly explain why only one ram in thee Rambouillet exhibits horns
horns for the Rambouillet is a sex linked found on the y chromosome since ewes don't have a y chromosome they do not display the horns
what is the primary purpose of a rotational crossbreeding system in a sheep operation
produce replacement ewes
breeding full brother to his sister will maximize the the inbreeding coefficient. what would be the inbreeding coefficient for this mating
if you felt that a rotational crossbreeding system in your operation was not practical how could you still be able to capitalize on your hybrid vigor of a single breed in your commercial ewe flock? what breed would you use?
what is it meant by the term epistasis when describing a gene expression? give an example
Expression of alleles at one locus influenced by alleles present at another locus. ex: wool color
if you were looking at east frisians ewes you would likely want them for their ability to do what?
produce lots of milk
crossbreeding is used often in a commercial sheep breeding program for what purpose
bring better traits to the flock and hybrid vigor
Katahdin breed is hardy, adaptable, and is acceptable in its muscling but its particularly unique in one other strength. whats this strength
whats an example of a composite breed in the U.S.
purebreds have unique breed characteristics that distinguish them from each other. what is the main breed characteristic between the Suffolk and the Hampshire breed
hamps have wool on their face/ head and legs whereas Suffolk do not
the polled dorset breed was developed at NC state by initially breeding 2 horned dorsets to each other. hows this possible?
this is possible because the polled gene is recessive which means that those 2 horned dorsets were heterozygous or in better terms carriers
whats an example of a qualitative trait? why is it easier to see selection progress when selecting for this type of trait
horns or spider lamb
easy because you either have the trait or you don't
hairy lamb syndrome is a genetic disease found in Southdown's breeds. if a sheep has been determined to be carrier of this gene thee 2 allels would look like what?
one would be a dominant gene and the other would bee a recessive gene (Hh)-> heterozygous
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