Download Are your Earlobes attached or detached?

Are your Earlobes attached or
detached?
 Is this genetic or environmental?
Which brand of vehicle do you
prefer?
 Is this genetic or environmental?
Which type of hairline do you have,
straight or widows peak?
 Is this genetic or environmental?
What is your favorite food?
 Is this genetic or environmental?
Do you have hair above your
knuckles?
 Is this genetic or environmental?
What is your favorite TV show?
 Is this genetic or environmental?
Can you roll your tongue?
 Is this genetic or environmental?
Do you have a hitchhikers thumb?
 Is this genetic or environmental?
What is your favorite drink?
 Is this genetic or environmental?
Are you a morning person or a
night owl?
 Is this genetic or environmental?
Animal Science
Genetics in History

Gregory Mendel


Priest from a monastery in
Europe.
Mendel was first to succeed at
predicting how traits are passed on
Genetics in History

Traits: characteristics that are inherited.

Heredity: the passing of traits from parent to offspring

Genetics : the study of heredity and traits
The Law of Segregation
 The Law of Segregation:
Every individual has two alleles of each gene.
 After meiosis,




Sperm cells have one allele for a trait
Ovum cells have one allele for a trait.
When combined at fertilization you have two
alleles for each trait.
Law of Independent Assortment
 Mendel concluded that different traits are
inherited independently of each other, so that
there is no relation, for example, between a
cat's color and tail length.
Genetics in History
 Garden peas reproduce sexually
 Male sex cells – sperm cells
 Female sex cells – ovum cells
Genetics in History
 Mendel selected garden peas because:
They can self pollinate
 He could control their traits.

Genetics in History
 P1 Generation

The original parent or the true breeding plant.
Genetics in History
 F1 Generation

The offspring of the parent (P1)
Genetics in History
 F2 Generation

The offspring of the (F1) generation.
Genetics in History
 Compare this to your family
 P1 generation – Your grand parents
 F1 generation – Your parents
 F2 generation – You
Genetics in History
 First Generation (P1)

Mendel cross pollinated tall pea plants with short
pea plants.

Mendel found that 
All the pea plants grew to be tall
The short trait had disappeared

Hybrid: offspring of the parents that have different forms of the trait

Genetics in History
 Second Generation (F1)
He allowed the first generation to selfpollinate.
 Planted the seeds from the self- pollination.

Genetics in History
 Discovered that:
 ¾ were as tall as the parent plants.

Dominant
Genetics in History
 ¼ were short like the parent generation.

Recessive
 They occurred in a ratio of 3:1
 The short trait reappeared.
Genetics in History
 Why did the Short Trait reappear?
 Because of the Rule of Dominance!
The Rule of Dominance
 Dominant traits:
The trait that shows up ¾ of the time.
 Shown with uppercase letters.
 TT

The Rule of Dominance
 Recessive traits:
The trait that shows up ¼ of the time.
 Shown with lowercase letters
 tt

The Rule of Dominance
 When identifying these traits we always use
the letter of the dominant trait!
Examples:
Polled = P
Black =B
Tall=T
Horned =h
White =b
Short=t
Genetics
 Homozygous:
 Genes that possess two dominant alleles or two recessive.
 TT or tt
Genetics
 Heterozygous:
 Genes that possess one dominant and one
recessive trait.
 Tt
Genetics
 Genotype:
 The genetic composition of an individual
 Example:
TT
Hh
ww
Genetics
 Phenotype:
 How the trait is expressed.
 Example:
Tall
Horned
Red/Black
Genetics
 Example:
 Two black calves might have the same phenotype, but
different genotypes.
 One may be Heterozygous, (Bb)
 One may be Homozygous, (BB)
The Punnet Square
 Mendel's pea plants
T
 Tall = TT
P1 Generation
t
T
t
T
t
t
T
t
T
t
 Short = tt
F1 Generation
T
The Punnet Square
 Mendel's pea plants
T
 Tall = Tt
F1 Generation
T
TT
T
t
t
T
t
tt
 Tall = Tt
F2 Generation
t
Incomplete Dominance
 What Happens when?
Incomplete Dominance
Incomplete Dominance

When traits are inherited incompletely, or they mix.
Red Shorthorn Cattle
Genotype (RR)
White Shorthorn Cattle
Genotype (R’R’)
Incomplete Dominance


When they reproduce
the offspring are both
red and white in
color.
New phenotype
occurs because the
trait that controls
pigment is affected.
Incomplete Dominance
R’
R’
R
R’R
R’R
R’R
R’R
R
Incomplete Dominance
R’
R
R’
R’R’
R’R
R’R
RR
R
Codominance



The expression of both alleles
Neither one of the alleles are
dominant or recessive, and is
expressed in the offspring.
Ex. - In some flowers, alleles for
petal color are codominant.
Codominance

Alleles are written with superscripts.
Genotype = PR PR
Phenotype = Red
Genotype = Pw Pw
Phenotype = White
Codominance
PR
PR
Pw
PRPW
PRPW
PRPW
PRPW
Pw
Law of Independent Assortment
 Mendel concluded that different traits are inherited
independently of each other, so that there is no relation,
for example, between a cat's color and tail length.
 This is actually only true for genes that
are not linked to each other.
Gender
 The sex of an animal is determined by the
sex chromosomes.

There are two types,


X shaped chromosomes
Y shaped chromosomes
 Vertebrate males have a XY
 Vertebrate females have a XX
Sex-linked Genes



Fruit Flies (Drosophila melanogaster) inherit sex
chromosomes the same as humans.
Traits located on the sex chromosomes are called sexlinked traits.
All sex-linked traits are located on the X
chromosomes.
Sex-linked Genes
Male Fruit Flies
Phenotype = White Eyes
Genotype = Xr Y
Female Fruit Flies
Phenotype = White Eyes
Genotype = Xr Xr
Sex-linked Genes
Xr
Y
XR
XRXr
XRY
XR
XRXr
XRY
Sex-linked Genes
XR
Y
XR
XRXR
XRY
Xr
XRXr
Xr Y
Meiosis
 Cell division where one body cell produces four gametes,
containing half the genetic material of the parent cell.
 Gamete: a cell which fuses with another during
fertilization.
Meiosis
 There are only two cells that have undergone Meiosis.
 Sperm Cells
 Egg Cells
Meiosis
 Sperm Cells
 Male reproductive cells
 Spermatogenesis
Meiosis
 Egg Cells
 Female Reproductive Cells
 Oogenesis
Meiosis
 Meiosis divided into two sections with a total of eight
phases.
 Meiosis 1
 Meiosis II
 These phases are continuous and flow one right after the
other.
Meiosis I
 Prophase 1
 Chromosomes Coil Up
 Chromosomes Line up in
Tetrads

Tetrad consists of two
homologous made up two
sister chromatids.
 Crossing over occurs
Meiosis I
 Metaphase 1
 Centromere becomes
attached by spindle fibers
 Tetrads line up along the
equator
Meiosis I
 Anaphase 1
 Chromosomes move to
opposite ends of the cell.
 Polar Ends
Meiosis I
 Telophase 1
 Spindle fiber breaks down
 Chromosomes uncoil
Meiosis II




Prophase II
Metaphase II
Anaphase II
Telophase II
 The above steps are exactly the same as mitosis.
Mitosis
 Prophase
 Metaphase
 Anaphase
 Telophase
Meiosis
 The end product of meiosis is four cells which are
genetically different then the parent cell, with half the
genetic information.
Meiosis
 ½ the information comes from the male sex cell
 ½ the information comes from the female sex cells
 When the two cells (gametes) combine all the necessary
genetic material is there.
Meiosis
 Fertilization
 The fusion of gametes to produce a new organism.
Meiosis
 Once the sperm and ovum have joined the fertilized egg
is called a zygote
Environmental Influences

The genetic make-up of an organism only
determines the potential of an organism.
Environmental Influences
 External Influences
 Temperature
 Light
 Nutrition
Environmental Influences
 Internal Influences
 Internal body functions


Hormones (ralgro, synovex)
Age
Environment vs. Heredity
An organism's traits and performance
are a sum total of its
ENVIRONMENT acting upon its
GENETIC information.
Environment vs. Heredity
Some TRAITS are influenced more by
an organism's ENVIRONMENT than
by its GENETICS, while others are
influenced more by genetics.
Heritability
 The percentage that a trait is affected by its genetic
information is called HERITABILITY.
 A heritability factor of 0.0 means that a trait is
influenced very little by genetic information
 A heritability factor of 1.0 means that a trait is
influenced very little by the environment.
Examples of Heritability
 Birth Weight = .40
 Weaning Weight = .30
 Multiple Births = 0.0 - 0.10
 Dressing Percentage = .60
Breeding Systems
Breeding Systems
 Purebred=a recognized strain established by breeding
individuals of unmixed lineage over many generations.
Breeding Systems
 Crossbreeding=A crossbreed refers to an animal with
purebred parents of two different breeds.
Breeding Systems
 Hybrid Vigor= Increased vigor or other qualities from
the crossbreeding of genetically different animals.
Breeding Systems
 • Average birth weight for the Black Baldie calves was 72 lb. — 3 lb. heavier
than the purebred sires, but extremely desirable and nearly ideal for commercial
operations.
 • At weaning the Black Baldie calves were 11.9 lb. heavier than the purebred
calves,
 • While both breed groups were similar for fat thickness (Angus = 0.52 vs.
Hereford = 0.54), Black Baldie steers had about 13 more lb. of carcass weight and
about ¾ of an inch more rib-eye area.
 • While feed conversion was nearly identical, Black Baldie steers outgained
the purebred steers by almost .15 of a lb. per day.
 • Heifer calves were bred and part of the group was marketed through the
Circle A Production Sale with the baldie average price $110 more than the straight
black heifers.
Breeding Systems
 Linebreeding=This is the breeding of animals that share
common ancestors but are not closely related. For
example the animals may share a common greatgrandparent.
 Inbreeding=This is the breeding of closely related
animals. Brother-Sister, Parent-Offspring, ½ brother - ½
Sister
Performance Pedigrees
summarizes a particular animal's own
performance records as well as
records of ancestors, siblings, and
progeny.
Progeny = offspring
EPD
EXPECTED PROGENY
DIFFERENCE
an INDICATION of the amount of
GENETIC merit that an animal will
pass on to its offspring.
EPD example
a bull with an EPD for weaning
weight of +25.0 pounds means that
the bull's offspring should average
25.0 pounds more at 205 days of age
than offspring of a bull with an EPD
for weaning weight of 0.0 pounds.
EPD Abbreviations
 BW = Birth Weight
 WW = Weaning Weight (205 days of age)
 YW = Yearling Weight (365 days of age)
 milk = maternal milking ability expressed in pounds of calf
weaned.
Adaptability
The ability of a BREED to become
SUITABLE to specific environmental
conditions
Type
a group of ANIMALS that are
grouped together according to the
PRODUCTS they produce
Examples -- Beef type cattle, Dairy
type cattle, Wool type sheep, Mutton
type sheep
Species
a group of ORGANISMS that have
several common
CHARACTERISTICS that
differentiate them from others.
Breed
animals having a common ORIGIN
and CHARACTERISTICS that
distinguish them from other groups
within the same SPECIES.