B70 Animal Genetics
Name ____________________________________
Date __________
Introduction
No two animals are exactly alike. Even with twins one may be taller, one may be
heavier, or grow faster.
What two main factors contribute to these differences in animals?
1.
2.
Phenotype
Define phenotype:
Define genotype:
Both the _________________________ and the ____________________________
affect the physical appearance of the animal.
Environmental Factors
The quantity and quality of the ______________
________________ conditions
Exposure to ___________________ and ________________________
The type of _______________________
How much influence does a livestock producer have over the animal’s environment?
How much influence does he have in the genetic make up of the animal?
Explain how the above information would influence the kinds of livestock management
practices that are going to have the greatest impact on the profitability of the operation?
Natural Selection
Explain natural selection:
Controlled breeding
A producer crosses two parents based on a desired outcome.
A tough, dominant, alpha male may not be a desirable trait for domestic animals.
Agriculture producers select for traits that have ____________________ importance.
List four traits of economic importance
1.
3.
2.
4.
The economically important traits are influenced by both the environment and the
genetic make up of the animal.
Controlled Breeding Programs
______________________: Breeding purebred animals with unrelated purebred
animals.
______________________: Breeding animals of the same species but of a different
breed.
Hybrid Vigor or Heterosis
A biological phenomenon which causes crossbreeds to _______________________
the average of their parents
This will achieve _______________ % immediate increase in yield.
The more __________________________ the breeds, the greater the heterosis:
(British breed crossed with Zebu breed)
Two-Breed Cross
Purebred bulls X purebred cows of another breed
Angus X Hereford = ___________________________
__________ % increase in weaning weight
Two-Breed Backcross or Crisscross
Breed A X Breed B = Crossbred calves
Crossbred X Breed A or B
Charolais Bull X Hereford Cow = Cross
Cross X Charolais
Yields _______ % of maximum heterosis
Three Breed Rotation Cross
3 Breeds (Angus, Simmental, Charolais)
Crossbred females bred to purebred bull of breed A
Resulting cross mated to purebred bull of breed B
Resulting cross mated to purebred bull of breed C
Repeat rotation
_______ % of maximum heterosis
Gene Transfer
All selection is based on the concept that desired characteristics are passed on from the
parents to the offspring.
Humans have _______ chromosomes. Each parent contributes ________.
Define Chromosome:
Define DNA:
Each gene is responsible for a particular trait.
Genes form a code or a blueprint for how the animal is to be formed.
One chromosome (strand of DNA) will attach to another forming a spiral shape called a
______________________________
Each half is bound together by substances called ________________________.
List the four main nucleotides.
1.
3.
2.
4.
Nucleotides are shaped so that each substance can pair with one particular nucleotide.
Adenine can only pair with _____________________
Cytosine can only pair with _____________________.
When cells undergo _____________________ and divide, each half replicates itself so
two strands exactly alike are formed. (DNA replication)
The genetic sequence on the DNA is used as a pattern for how the animal is to be
constructed. ________________________ reads the pattern and transfers the
information the rest of the cell.
Genetic Engineering
Genetic engineering is a technology that allows specific genetic information or traits to
be built into or engineered into the genes of a species.
In genetic engineering, segments of DNA are ___________ and ________________
into existing DNA placing new genetic information into the existing DNA.
Differentiation
As the embryo begins to grow and develop, cells differentiate. Some cells develop into
___________________ and ________________, some into ____________ and some
into ______________________________.
The process of how cells differentiate is not fully understood.
Sex cells called __________________________ undergo _________________ and
only carry one strand of DNA.
At conception, chromosome halves from each parent combine to form a paired
chromosome.
There is almost an infinite number of ways that the genes can be arranged on a strand
of DNA. This arrangement determines the make up of the new animal.
Alleles
Each male gene that controls a specific trait combines with the female gene for the
same trait.
A pair of genes that control a specific trait are called ______________________.
If both genes that control a specific trait are alike, they are said to be
___________________.
For example: if the male gene for hair color is black and the female gene that controls
hair color is also black.
Gene Dominance
If they are different (black & red) they are said to be _________________________.
In this case one gene will be ___________________________, and determine coat
color.
Dominant Gene = trait overpowers others
How are recessive genes expressed? ____________________________________
Gene Dominance
P = _____________
p = _____________
Define genotype:
Define phenotype:
Punnett Squares
1. A homozygous horned cow (pp) is mated to a homozygous polled bull (PP),
What is the genotypic result of this cross? ________________
What is the phenotypical result of this cross? _______________
2. If a homozygous horned cow (pp) is bred with a heterozygous polled bull (Pp),
What is the Genotypic result of this cross? ________________
What is the phenotypical result of this cross? _______________
3. If two heterozygous polled animals are mated.
What is the genotypic result of this cross? ________________
What is the phenotypical result of this cross? _______________
Define a monohybrid cross:
Define a dihybrid cross:
4. If an Angus bull that is homozygous black and polled (BBPP) is mated to a red
shorthorn cow that is homozygous red and horned (bbpp).
BBPP can be simplified to BP (Black & Polled)
bbpp can be simplified to bp (RED & Horned)
What is the genotypic result of this cross? ________________
What is the phenotypical result of this cross? _______________
5. If two of the offspring which are heterozygous for black/red and polled/horned (BbPp)
are mated.
How do you do a Punnett square for two heterozyous animals?
Use all possible gene combinations
Both the bull and cow are BbPp.
What are the possible contributions?
BP, Bp, bP,bp for both animals. (4 x 4 grid)
What is the genotypic result of this cross?
What is the phenotypical result of this cross?
Black Polled =
Black Horned =
Red Polled =
Red Horned =
6. When a heterozygous bull (BbPp) is mated to a homozygous cow (BBPP)
What are the outcomes?
7. If a (BbPp) bull is mated to a (BBPp) cow.
What are the outcomes?
Mendilin Genetics
8. Paint color is desirable characteristic of paint horses and is dominate to solid color.
If a homozygous dominant stallion is bred with a solid colored mare, how likely is it that
a paint foal would result?
9. What if the stallion is heterozygous for paint color, how likely is it that I will get a paint
foal?
Codominate Genes
Some alleles may have _____________ dominate genes.
Shorthorn cattle are ___________, ______________, and _______________
Red shorthorns carry the gene for red coat color RR
White shorthorns carry the gene for white coat color WW
Cattle that are roan or spotted carry a gene for red and a gene for white RW
Both are dominant, creating a spotted or roan colored animal.
The Additive Expression of Genes
Instead of a single pair a number of genes may be added together to produce a single
trait.
Examples:
_______________ production is controlled by several genes.
Size and ________________________ of the female
__________________ production
__________________ size and function
Rate of _____________________
___________________________
Genetic Mutations
Occasionally a defect will happen and genetic traits are not passed on as intended.
Example: two headed calves.
Explain the difference between an abnormality and a genetic mutation?
Sometimes genetic mutations can be used to introduce new kinds of species.
_____________________________________
Determining an Animal’s Sex.
Whether a mammal is a male or a female is determined upon _________________.
_____________________ (sex cell) contains ___________ of the sex chromosome
from the parent.
The female chromosome is referred to as _________.
When the chromosome divides and half goes to the offspring each half is the same.
The male chromosome is referred to as _______. When divided, a gamete will be either
X or Y.
When the male and female gametes combine they will either be XX Female or XY male.
What is the probability of a male child being conceived over a female?