Genetics. What is Selection ? Mating animals to produce certain characteristics Low Birthweight...
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Transcript of Genetics. What is Selection ? Mating animals to produce certain characteristics Low Birthweight...
GeneticsGenetics
What is What is SelectionSelection??
• Mating animals to produce certain characteristics
• Low Birthweight• Heavier Weaning Weight• Color• Horned or Polled• Temperment
What makes an animal What makes an animal they way that they are?they way that they are?
• Animals are the result of Feed, Health, and Inheritance (genetic material)
• Feed is fastest to correct• Genetics last longest
What is What is GeneticsGenetics??• All body cells contain “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 What are Dominant Dominant GenesGenes??
• Dominant Genes = one gene overshadows the other
• Angus Cattle: black is dominant, red is not (Bb)
• Hereford: white face is dominant (Ww)
• Hampshire Hog: white belt is dominant
• Horns are dominant (Pp)
What are What are Recessive Recessive GenesGenes??
• 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 = horned• p = polled• If a homozygous horned cow
(PP) is mated to a homozygous polled bull (pp), what percent of the calves will be horned, polled?
Punnet SquarePunnet SquareP P
p
p
Pp Pp
Pp Pp
Punnet SquarePunnet Square
• If a homozygous horned cow (PP) is mated to a heterozygous horned bull (Pp), what percent of the calves will be polled?
Punnet SquarePunnet SquareP P
p
p
Pp Pp
Pp Pp
What are What are Sex Linked Sex Linked GenesGenes??
• 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: What sex Punnet Square: What sex will the offspring be?will the offspring be?
X Y
X XX XY
XX XYX
If Dad is bald, will you be If Dad is bald, will you be bald?bald?
X Y
X XX X Y
XX XYX
B
B
B
Baldness is carried by the Baldness is carried by the mothermother
X Y
X XX X Y
XX XYX
BB B
What is Mom is bald?What is Mom is bald?
X Y
X XX X Y
XX XYX
BB B
B B B
What is What is Incomplete Incomplete DominanceDominance??
• If both genes express themselves
• Shorthorn Cattle: Red male mated to a White female = Roan calf
• RR + 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?
Shorthorn: Red X WhiteShorthorn: Red X WhiteR R
W
W
RW RW
RW RW
Punnet SquarePunnet Square
• If a red bull (RR) is mated to a roan (RW) cow, what color will the calves be?
Shorthorn: Red X RoanShorthorn: Red X RoanR R
R
W
RR RR
RW RW
What if Both Parents are What if Both Parents are Roan?Roan?
R W
R
W
RR RW
RW WW
Undesirable Undesirable CharacteristicsCharacteristics
• Dwarfism• Monorchid = only one testicle
descends• Cryptorchid = no testicles
descend• Short ears & tails
What is a What is a MutationMutation??• 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 Abnormality?What is an Abnormality?
• Similar to a Mutation, only it is caused by something in the environment
• Siamese twins
What is Heritability?What is 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
What is What is Hybrid VigorHybrid Vigor??• Offspring will outperform either
of the parents• 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
What are What are ExoticsExotics??
• Animals not common to United States
• Difficult to define today• New breeds are exotics
Genetic TermsGenetic Terms
• Genotype: genetic makeup (Bb)
• Phenotype: physical appearance (Black)
• Heterosis: Genes are different, Dominant & Recessive (Bb)
• Homozygous: both genes are the same (BB or bb)