Breeding Programmes Flashcards
What are breeding programmes?
- They usually involve selective breeding of animals to develop specific, desirable phenotypic (or genetic) traits
- Typically done with domesticated species & results in specific breeds or crossbreeds
What are 4 economic reasons for breeding programmes?
- Food
- Pets
- Clothing materials
- Medicines
What is a functional reason for breeding programmes?
- Breeding animals for a specific purpose, e.g. dog breeds
How are breeding programmes used for conservation purposes?
- Produce animals for zoos, aquaria,
research & education - Increase captive populations of threatened or
endangered species - Re-introduction into the wild
What are 4 negative effects of captive breeding programmes?
- Lose genetic variability so cannot
easily adapt to environmental change
• Result in inbreeding
• May not develop skills needed to survive in the wild if re-introduced
• Assumes there is suitable habitat into which
they can be re-introduced
For optimum results, what 4 things do breeding programmes need to do?
- Select the correct individuals to use
- Select the correct number of animals to use
- Select what breed/species to use
- What breeding strategy to use
Why does species crossing rarely work?
- Gene dosage effects (increased expression
of certain genes due to different numbers of
gene copies) - Reduced fertility due to inability to carry out meiosis correctly (e.g.
different chromosome numbers)
What is inbreeding?
The production of offspring from
mating animals that are closely related
genetically
What does inbreeding result in?
- Decreased fitness in a population (inbreeding depression)
- Homozygosity, which can increase chances of offspring being affected by recessive or deleterious recessive traits
Why is inbreeding commonly used in selective breeding?
- Carried out in purebred lines to ‘fix’ desirable traits in modern breeds of animals
Name 3 male reproductive defects as a result of inbreeding.
- Impaired sperm mobility
- Reduced semen
- Increased incidence of cryptorchidism
What effect on species survival might inbreeding have?
- Individuals of a species may become so alike,
that they cannot easily adapt to environmental
changes & evolve - Increases extinction risk
Give an example of a species with high levels of inbreeding but no obvious ill-effects
The Chillingham wild white cattle herd in Northumberland
What benefits can inbreeding have in animal breeding systems given the correct selection criteria?
- Remove deleterious recessive genes from
population - Increase uniformity – particularly important
if breeding for qualitative traits such as coat
colour or meat yield
What is inbreeding depression?
A decline in performance (e.g. vigour, size, fertility)
What is line breeding?
- A form of interbreeding
- Usually involves crosses between individuals & their descendants)
- Used to ‘fix’ desirable traits in a breed
without as high a risk of producing undesirable
traits that may occur with close inbreeding
What is outbreeding?
- Mating between individuals from different populations (usually geographically distinct populations with no gene flow between them) or even different subspecies
- Can increase reproductive fitness
by increasing heterozygosity and preventing
the expression of deleterious recessive allele
What does mating ‘like to like’ mean?
- Involves choosing animals based on appearance
- E.g. two yellow Labradors
- This is often practised in dog/cat breeding
What does making ‘unlike to unlike’ mean?
- If the animals you are breeding are failing in some
respect, you mate them with animals that excel
in that characteristics
What is outbreeding depression?
- A decline in reproductive fitness
- Less common
- Can result from chromosomal incompatibilities and genetic drift etc.
What is chromosomal incompatibility?
Where 1 individual is missing a chromosome from a pair (monosomy) or has more than 2 chromosomes of a pair (trisomy)
- Can result from structural differences (e.g. deletions, duplications or translocations)
Compare inbreeding & outbreeding (4 points)
- Definitions - Inbreeding is mating 2 genetically
closely related parents over 4 to 6
generations whereas outbreeding is breeding between distantly related or unrelated individuals
selected from two populations - Offspring - more likely to be homozygous from inbreeding whereas outbreeding increases heterosis or hybrid vigour
- Fitness - Lower biological fitness in offspring from inbreeding
- Genetic variation - reduced in inbreeding, increased in outbreeding
What is crossbreeding?
- Breeding between purebred parents of 2 different breeds or varieties
- Offspring’s are crossbreeds
What is back crossing?
- A crossing of a hybrid with one of its parents or an individual genetically similar to its parent
- Aims to transfer a desirable trait in an animal of inferior genetic background to an animal or preferable genetic background
What is Eugenics?
Selectively breeding individuals who have ‘desired traits’
