GenetiGeneticscs

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

p p

P

P

Pp Pp

Pp Pp

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?

Punnet SquarePunnet Square

P p

P

P

PP Pp

PP Pp

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

If dad is bald, will you If dad is bald, will you be bald?be bald?

X Y

X X X X Y

X X XYX

BB

BB

BB

Baldness is carried by Baldness is carried by the motherthe mother

X Y

X X X X Y

X X X YX

BBBB BB

What if mom is What if mom is bald?bald?

X Y

X X X X Y

X X X YX

BBBB BB

BB BB BB

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?

Shorthorn: Red X Shorthorn: Red X WhiteWhite

R 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: Shorthorn: Red X RoanRed X Roan

R R

R

W

RR RR

RW RW

What if Both What if Both Parents are Roan?Parents are 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 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

What are What are Exotics?Exotics?

•Animals not common to United States

•Difficult to define today•New breeds are exotics