1. Genetics

2. What is Genetics?
• 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

3. What are Dominant Genes?
• 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)

4. What are Recessive 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

5. Punnet 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?

6. Punnet Square
P
P
p
Pp
Pp
p
Pp
Pp

7. Punnet Square
• If a homozygous horned cow (PP) is
mated to a heterozygous horned bull
(Pp), what percent of the calves will be
polled?

8. Punnet Square
P
P
p
Pp
Pp
p
Pp
Pp

9. What are Sex Linked 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

10. What is Incomplete
Dominance?
• If both genes express themselves
• Shorthorn Cattle: Red male mated to a
White female = Roan calf
• RR + WW = RW

11. Punnet 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?

12. Shorthorn: Red X White
R
R
W RW RW
W RW RW

13. Punnet Square
• If a red bull (RR) is mated to a roan
(RW) cow, what color will the calves
be?

14. Shorthorn: Red X Roan
R
R RR
R
RR
W RW RW

15. What if Both Parents are
Roan?
R
R
W
RR
RW
W RW WW

16. What is a 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

17. What is an Abnormality?
• Similar to a Mutation, only it is caused
by something in the environment
• Siamese twins

18. 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

19. Heritability
• 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?

20. Heritability
• What is the difference in current
weaning wt and that of the new ram?
110 - 70 = 40 lbs
• Heritability % x difference
30% x 40 = 12 lbs
• Can expect a gain in weaning wt of 12
lbs
• 70 lbs + 12 lbs = 82 lbs

21. What is Hybrid 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

22. Genetic Terms
• Genotype: genetic makeup (Bb)
• Phenotype: physical appearance
(Black)
• Heterozygous: Genes are different,
Dominant & Recessive (Bb)
• Homozygous: both genes are the same
(BB or bb)