genetics. genetics terms heterozygous = two different types of genes (bb) homozygous = two similar...
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Genetics TermsGenetics Terms• Heterozygous = two different
types of genes (Bb)• Homozygous = two similar
genes (BB)• Dominant Gene = trait
overpowers others• Recessive Gene = must be
accompanied with another recessive gene to express trait
• Incomplete Dominance = both traits express themselves
Genetic TermsGenetic Terms•Genotype - genetic makeup (Bb)
•Phenotype - physical appearance (Black)
•Heterosis - Genes are different, Dominant & Recessive (Bb)
What is Selection?What is Selection?•Mating animals to produce certain characteristics
•Low Birth Weight•Heavier Weaning Weight•Color•Horned or Polled•Temperment
What makes an What makes an animal the way it animal the way it
is?is?•Animals are result of FeedFeed, HealthHealth, and InheritanceInheritance (genetic material)
•Feed is fastest to correct
•Genetics last longest
What are What are Genetics?Genetics?
• All body cells contain “Blueprints”“Blueprints” with instructions as to how an animal will look or act, etc.
• One Gene comes from each parent (pairs)
• Genes are divided into sections (Chromosomes) that carry genes
• Sex chromosomes: –male = XY, –female = XX
What are Dominant What are Dominant Genes?Genes?
• Dominant Genes are traits that overpower other types of genes
• Angus Cattle: black(B) color dominant, red (b) color recessive (Bb)
• Hereford: white (W) face cattle dominant over colored (w) recessive (Ww)
• Hampshire Hog: white (W) belt dominant, color (w) recessive (Ww)
• Polled (P) cattle are dominant over horned (p) recessive (Pp)
• Black (B) horses dominate, brown (b) recessive (Bb)
What are Recessive What are Recessive Genes?Genes?
•The gene that is overshadowed by a dominant gene
•Recessive genes can only express themselves if both genes are recessive
•Polled vs Horned (Pp) (pp)•Black wool vs white (Ww) (ww)•Dwarfism vs normal size (dd)•Albino
Punnet SquarePunnet Square
•P = polled•p = horned•If a homozygous polled cow (PP) is mated to a homozygous horned bull (pp), what percent of the calves will be horned, polled?
Punnet SquarePunnet Square
•If a homozygous polled cow (PP) is mated to a heterozygous horned bull (Pp), what percent of the calves will be polled?
What are Sex Linked What are Sex Linked Genes?Genes?
• Some recessive genes are attached to the X and Y chromosomes
• Humans: Colorblindness and Baldness are on the X chromosomes
• In Men, traits expressed anytime present
• In Women, must have two recessives to show trait
• Children get baldness from mothers
Punnet Square:Punnet Square: What sex will the What sex will the
offspring be?offspring be?
X Y
X XX XY
XX XYX
What is What is Incomplete Incomplete Dominance?Dominance?
•If both genes express themselves
•Shorthorn Cattle: Red male mated to a White female = Roan calf
•RR + WW = RWRR + WW = RW
Punnet SquarePunnet Square•Shorthorn Cattle•R = Red•W = white•RW = roan•If a red bull (RR) is mated to a white cow (WW), what color will the calves be?
Punnet SquarePunnet Square
•If a red bull (RR) is mated to a roan (RW) cow, what color will the calves be?
Undesirable Undesirable CharacteristicsCharacteristics
•Dwarfism•Monorchid = only one testicle descends
•Cryptorchid = no testicles descend
•Short ears & tails
What is a What is a Mutation?Mutation?
• Dramatically different from what is expected genetically
• Horned calf from polled parents• Loss of some or extra body parts• Lethal Mutation: causes death
at birth• Sublethal Mutation: limits
animals ability to grow to maturity
• Beneficial Mutation: loss of tail in lambs
What is an What is an Abnormality?Abnormality?
•Similar to a Mutation, only it is caused by something in the environment
•Siamese twins
What is What is Heritability?Heritability?
•Chance that traits will be inherited
•Low: multiple births, fat covering
•Medium: birth wt, wean wt, milk, wool grade, carcass wt, rate of gain
•High: Loin eye area, fleece length & quality
HeritabilityHeritability•Currently have ewes that wean
70 lb lambs•Want to raise weaning wt to 110
lbs•Select a ram with a wean wt of
110 lbs•Heritability of weaning wt is
30%•What can you expect new lamb
crop to weigh at weaning?
HeritabilityHeritability•What is the difference in current weaning wt and that of the new ram?110 - 70 = 40 lbs
•Heritability % x difference30% x 40 = 12 lbs
•Can expect a gain in weaning wt of 12 lbs
•70 lbs + 12 lbs = 82 lbs
Mating SystemsMating Systems•Random Mating: all males have
an equal opportunity to mate with all females
•Outcrossing: mating purebreds with unrelated purebreds
• Inbreeding: mating related animals– Linebreeding: parents mated to
offspring•Crossbreeding: mating animals
of same species but different breeds
CrossbreedingCrossbreeding•mating of animals of different breeds
•can increase productivity•produce animals with combination of traits
•foundation stock for new breeds
•introduce new genes quicker than in purebreds
What is Hybrid What is Hybrid Vigor?Vigor?
• Offspring will out-perform either of the parents, also know as heterosis.
• Corn Breed A yields 100 bu/acre• Corn Breed B yields 100 bu/acre• Crossbreed A & B yields corn that
yields 200 bu/acre• Vigor only expressed in
crossbreeding• Donkey mated to a horse = Mule
– mule is sterile