Intro to Agriculture
AAEC – Paradise Valley
Spring 2015
 Heredity is the
transmission of genetic
or physical traits from
parent to offspring.
 Austrian Monk
 Considered the “Father of
Heredity”
 He conducted plant breeding
experiments in their monastery
garden.
 In 1865 he made his work
public, units of inheritance.
 Each of the 100 Trillion cells in our body except
the red blood cells contains the entire human
genome, in the nucleus of every cell is the genetic
information “blueprint” to construct the
individual.
 It is the Deoxyribonucleic acid (DNA)
 Function of DNA
 Genetic code for almost every organism.

Provide template for protein synthesis.
 The DNA in every cell is located in rod like
segments called chromosomes
 Chromosomes occurs in pairs in every cell of
our body except in the sperm and ovum.
 Chromosomes numbers are the same for each
species.
Species
Cattle
Swine
Sheep
Horse
Human
Chicken
Goat
Donkey
Diploid #
60
38
54
64
46
78
60
62
Haploid #
30
19
27
32
23
39
30
31
 Females contribute an X chromosome towards the
sex of their offspring.
 Males can contribute an X or a Y chromosome
toward the sex of their offspring.
 Absence of an Y chromosome results in a the
embryo developing into a female.
 Presence of an Y chromosome results in the
embryo developing into a male.
Chromosomes contains several units of
inheritance “genes”.
Genes usually occurs in pairs, one from each
parent.
Some traits are inherited directly from one
set of genes.
Some traits are inherited through several sets
of genes.
 Homozygous – contains 2 identical genes for the
same trait (ie. AA, BB, cc)
 Heterozygous – contains 2 different genes for the
same trait (ie. Aa, bB, Cc)
 Phenotype – Outward appearance of a trait, coat
color, polled, horned.
 Genotype – Genetic classification of a gene, AA,
Aa, aa.
 Allele- Location of a gene on the chromosome.
Genotype contains two copies of the gene.
 AaBB
Gamete (sex cells) contains only one copy of
the gene.
 AB
Determine the possible gametes of AaBB
 AB
aB
 State if its a gamete or genotype.
Genotype
1. Aa
2. D Gamete
3. DdEeFFgg Genotype
4. sRtxyq Gamete
5. AaBBeeFF Genotype
6. adgEFT Gamete
From the genotype AaBb
 AB
 Ab
 aB
 ab
Write all this…
 The gene that express itself, the powerful and
dominant gene.
 It has the power to overshadow the recessive gene
when there is complete dominance.
 Some examples are:
 White faced in cattle
 Droopy ears in swine
 Polled in cattle
 Black coat color in Angus cattle
Write all this…
 The gene that is overshadowed by a dominant gene
 Recessive genes can only express themselves in the
absence of the dominant gene
 Polled vs Horned (Pp) (pp)
 Black wool vs white (Ww) (ww)
 Dwarfism vs normal size (dd)
 Albino
 Angus - Black coat color is dominant.
 BB = Homozygous Dominant and Black
 Bb = Heterozygous and is black
 bb = Homozygous recessive and red
 A heterozygous bull is mated to 50 homozygous recessive
cows.
 How many calves are black?
 How many calves are red?
 What is the genotypic and phenotypic ratios?
B
b
b
Bb
bb
b
Bb
bb
 2 Heterozygous = Bb
 2 Homozygous Recessive = bb
 25 Black, 25 Red
 Genotypic ratio = 0:2:2
 Phenotypic ratio =
2 Black: 2 Red
 Let's say that in seals, the gene for the length of the whiskers
has two alleles. The dominant allele (W) codes long whiskers
& the recessive allele (w) codes for short whiskers.
A. What percentage of offspring would be expected to have
short whiskers from the cross of two long-whiskered
seals, one that is homozygous dominant and one that is
heterozygous?
B. If one parent seal is pure long-whiskered and the other is
short-whiskered, what percent of offspring would have
short whiskers?
 In purple people eaters, one-horn is dominant and no horns
is recessive. Draw a Punnet Square showing the cross of a
purple people eater that is hybrid for horns with a purple
people eater that does not have horns. Summarize the
genotypes & phenotypes of the possible offspring.
 Mendel found that crossing wrinkle-seeded plants with pure
round-seeded plants produced only round-seeded
plants. What genotypic & phenotypic ratios can be
expected from a cross of a wrinkle-seeded plant & a plant
heterozygous for this trait (seed appearance)?
 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
Y
X B
X
X
X X
B
X X
B
X Y
X Y
X
X B
X
X X B
X X
Y
X BY
X Y
X
X B
X B
X X B
X X B
Y
X BY
XB
Y
If both genes express themselves
 Shorthorn Cattle: Red male mated to
a White female = Roan calf
 RR crossed rr = Rr
Shorthorn Cattle
 RR = Red
 rr = white
 Rr = roan
If a red bull (RR) is mated to a white cow
(rr), what color will the calves be?
R
R
r Rr
Rr
r Rr
Rr
If a red bull (RR) is mated to a roan
(Rr) cow, what color will the calves be?
R
R
R
RR
RR
r
Rr
Rr
R
r
R
RR
Rr
r
Rr
rr
 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
Chance that traits will be
inherited
 Low: multiple births, fat
covering
 Medium: birth weight wean
weight, milk, wool grade,
carcass weight, rate of gain
 High: Loin eye area, fleece
length & quality
 Upgrading: mating purebreds with
grade animals
 Inbreeding: mating closely related
animals
 Linebreeding: mating distantly
related animals
 Outcrossing: mating unrelated
animals in the same breed.
 Crossbreeding: mating animals of
same species but different breeds.
 Offspring will outperform either of the
parents
 Example:
 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