Breeding Programmes

Question 1

What are breeding programmes?

Answer 1

• 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

Question 2

What are 4 economic reasons for breeding programmes?

Answer 2

• Food
• Pets
• Clothing materials
• Medicines

Question 3

What is a functional reason for breeding programmes?

Answer 3

• Breeding animals for a specific purpose, e.g. dog breeds

Question 4

How are breeding programmes used for conservation purposes?

Answer 4

• Produce animals for zoos, aquaria,
  research & education
• Increase captive populations of threatened or
  endangered species
• Re-introduction into the wild

Question 5

What are 4 negative effects of captive breeding programmes?

Answer 5

• 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

Question 6

For optimum results, what 4 things do breeding programmes need to do?

Answer 6

• 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

Question 7

Why does species crossing rarely work?

Answer 7

• 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)

Question 8

What is inbreeding?

Answer 8

The production of offspring from
mating animals that are closely related
genetically

Question 9

What does inbreeding result in?

Answer 9

• Decreased fitness in a population (inbreeding depression)
• Homozygosity, which can increase chances of offspring being affected by recessive or deleterious recessive traits

Question 10

Why is inbreeding commonly used in selective breeding?

Answer 10

• Carried out in purebred lines to ‘fix’ desirable traits in modern breeds of animals

Question 11

Name 3 male reproductive defects as a result of inbreeding.

Answer 11

• Impaired sperm mobility
• Reduced semen
• Increased incidence of cryptorchidism

Question 12

What effect on species survival might inbreeding have?

Answer 12

• Individuals of a species may become so alike,
  that they cannot easily adapt to environmental
  changes & evolve
• Increases extinction risk

Question 13

Give an example of a species with high levels of inbreeding but no obvious ill-effects

Answer 13

The Chillingham wild white cattle herd in Northumberland

Question 14

What benefits can inbreeding have in animal breeding systems given the correct selection criteria?

Answer 14

• Remove deleterious recessive genes from
  population
• Increase uniformity – particularly important
  if breeding for qualitative traits such as coat
  colour or meat yield

Question 15

What is inbreeding depression?

Answer 15

A decline in performance (e.g. vigour, size, fertility)

Question 16

What is line breeding?

Answer 16

• 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

Question 17

What is outbreeding?

Answer 17

• 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

Question 18

What does mating ‘like to like’ mean?

Answer 18

• Involves choosing animals based on appearance
• E.g. two yellow Labradors
• This is often practised in dog/cat breeding

Question 19

What does making ‘unlike to unlike’ mean?

Answer 19

• If the animals you are breeding are failing in some
  respect, you mate them with animals that excel
  in that characteristics

Question 20

What is outbreeding depression?

Answer 20

• A decline in reproductive fitness
• Less common
• Can result from chromosomal incompatibilities and genetic drift etc.

Question 21

What is chromosomal incompatibility?

Answer 21

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)

Question 22

Compare inbreeding & outbreeding (4 points)

Answer 22

1. 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
2. Offspring - more likely to be homozygous from inbreeding whereas outbreeding increases heterosis or hybrid vigour
3. Fitness - Lower biological fitness in offspring from inbreeding
4. Genetic variation - reduced in inbreeding, increased in outbreeding

Question 23

What is crossbreeding?

Answer 23

• Breeding between purebred parents of 2 different breeds or varieties
• Offspring’s are crossbreeds

Question 24

What is back crossing?

Answer 24

• 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

Question 25

What is Eugenics?

Answer 25

Selectively breeding individuals who have ‘desired traits’