Animal
Genetics
Animal Genetics
The body is made up of millions of tiny cells
The contents of the
cell is called
protoplasm.
Animal cells are the smallest living things in
the world. Animals are made purely of cells.
Animal Genetics
The Cell Components
Nucleus
Gives cells the ability to grow, to digest food
and to divide, contains chromosomes
composed of genes.
Cytoplasm
Gives the cell shape and contains components
necessary for cell functions.
Animal Genetics
The Cell Components
Cell Membrane
Outside of the cell, allows only certain
materials to pass in and out of the cell.
Animal Genetics
Nucleus
Cytoplasm
Cell
Membrane
Animal Genetics
Cell Division
Mitosis
Increases total number of cells
Results in animal growth
Chromosomes pairs are duplicated
Animal Genetics
Cell Division
Meiosis
Produces gametes
Only have one-half the chromosomes of
normal cells
Animal Genetics
Chromosomes
Rod shaped bodies
Made of proteins
Found in the
nucleus of the cell
Exist in pairs
Except in gamete
cells (single
chromosome)
Animal Genetics
Chromosomes
The number of chromosome pairs differs
for various animals
COW
30
HORSE
33
PIG
19
CHICKEN
6
HUMAN
23
Animal Genetics
Genes
Located on chromosomes
Thousands found in each animal
Inherited from parents
Control inherited characteristics
Carcass traits
Growth rate
Feed efficiency
Animal Genetics
Genes
Two types of inherited traits
Dominant
Recessive
Gene combinations
Heterozygous
Homozygous
Animal Genetics
Genes
Dominant gene
Hides the effect of another gene
Polled condition in cattle is dominant
The gene is represented by a capital letter
Dominant Gene
Animal Genetics
Genes
Recessive gene
Gene that is hidden by another
The gene is represented by a lower case
letter
Recessive Gene
Animal Genetics
Examples of Dominant and
Recessive Genes
The dominant gene is written- P
The recessive gene is written-p
P= Polled
p= horned
Animal Genetics
Gene Combinations
Homozygous gene pair
Carries two genes for a trait
Polled cow might carry the gene PP
Heterozygous gene pair
Carries two different genes that affect a trait
Polled cows might carry a recessive gene
with the dominant Pp
Animal Genetics
Predicting Genetics
Genotype
Kind of gene pairs possessed
Phenotype
The physical appearance of an animal
Punnett squares
Are used to predict genotypes and
phenotypes of animals
Animal Genetics
Predicting the Polled Trait Using
the Punnett Square
Polled Sire
Polled Dam
P
P
P
PP
PP
P
PP
PP
Both parents are
dominant homozygous
for the polled trait
All offspring will be
dominant homozygous
for the polled trait
Animal Genetics
Predicting Dwarfism
Using the Punnett Square
Carrier Sire
Normal Dam
A homozygous parent
N
N
N
NN
NN
n
Nn
Nn
crossed with a
heterozygous parent
Two offspring will be
homozygous for the normal
trait and two offspring will
be heterozygous (carriers
of dwarfism)
Animal Genetics
Predicting Coat Color Using the Punnett Square
BW Sire (carrier)
BW Dam (carrier)
B
b
B
BB
Bb
b
Bb
bb
Both parents are
heterozygous (carriers for
the recessive coat color)
One offspring will be
homozygous dominant, two
will be heterozygous, and
one offspring will be
homozygous recessive
The normal coat color of Holstein cows is black and white (BW) the recessive
color is red and white (RW)
Animal Genetics
Predicting Coat Color Using the Punnett Square
RW Sire
BW Dam (carrier)
B
b
b
Bb
bb
b
Bb
bb
A heterozygous parent
(carrier) crossed with a
recessive homozygous
parent
Two offspring will be
heterozygous (carriers) and
two offspring will be
homozygous recessive
The normal coat color of Holstein cows is black and white (BW) the recessive
color is red and white (RW)
Animal Genetics
Writing Genotypes and Phenotypes Using the
Punnett Square
RW Sire
BW Dam (carrier)
B
b
b
Bb
bb
b
Bb
bb
Genotypes
• Bb and bb
Phenotypes
• Black and White Coat
• Red and White Coat
The normal coat color of Holstein cows is black and white (BW) the recessive
color is red and white (RW)
Animal Genetics
Heritability
Estimates the likelihood of a trait being
passed on from the parent to the offspring
Low heritability
Slow herd improvement
High heritability
Faster herd improvement
Animal Genetics
Heritability
Heritability for carcass traits are higher
than reproductive traits
Low heritability is improved most through
environment
High heritability is improved most through
selective breeding and environment
Estimates vary from 0 to 70%
Swine rates are usually lower than cattle
Animal Genetics
Heritability Estimates
Fertility
10%
Birth Weight
40%
Weaning Weight
25-30%
Yearling Weight
60%
Tenderness
60%