Applied genetics 1 + 2

Question 1

What is quantitative genetics?

Answer 1

Inheritance of quantitative traits - traits we measure
Usually influenced by several genes at different loci
To study them we need to study populations
Most of the traits of economic interest

Question 2

List 2 examples of traits we measure

Answer 2

Milk yield
Muscle growth rate

Question 3

Can quantitative traits be influenced by the environment?

Answer 3

Yes

Question 4

The phenotype consists of…?

Answer 4

Genotype + Environment

Question 5

Genetic improvement of a trait requires … ?

Answer 5

… variability between the animals of the population we want to improve

Question 6

Define heritability

Answer 6

Heritability is the part of the phenotypic variation that is due to heritable gene effects

Question 7

What does a trait having a ‘high heritability estimate’ mean?

Answer 7

That we can more easily improve that trait through genetic selection

Question 8

List 3 traits that have a high heritability

Answer 8

Body conformation
Udder morphology
Milk fat/protein %

Question 9

What are phenotypic correlations?

Answer 9

Measure the direction and strength of association between observed performance/phenotypes (eg milk yield/ protein, live weight/ fat depth)

Question 10

What are genetic correlations?

Answer 10

Direction and strength of association between genetic merit for two traits

Question 11

What are breeding valves?

Answer 11

• Refers to the additive genetic merit of an animal
• Predicted from information including animal’s own performance and performance of its relatives

Question 12

What do positive, negative or zero breeding values indicate?

Answer 12

Whether the animal is genetically above or below the mean

Question 13

What is Bovine Leucocyte Adhesion Deficiency and its the consequence of this?

Answer 13

• Single point mutation (adenine to guanine) at position 383 of the CD18 gene
• Impaired expression of the beta-2 integrin of the leukocyte adhesion molecule of neutrophils

-> Fewer neutrophils get into tissue to fight infection

Question 14

What are the clinical signs of Bovine Leucocyte Adhesion Deficiency?

Answer 14

• Ulcers on oral mucosa, gingivitis/periodontitis, chronic pneumonia and recurrent or chronic diarrhoea
• Die due to the infectious complications < 1 year old

Question 15

How is Bovine Leucocyte Adhesion Deficiency treated?

Answer 15

None in practice
-> Repeated antibiotic therapy without diagnosis wasting farmers money

Question 16

What is Complex Vertebral Malformation?

Answer 16

• Autosomal recessive
• Mis-shapen and fused vertebrae around the cervico-thoracic junction, symmetrical arthrogryposis of the limbs
• 50% have cardiac abnormalities

Question 17

List some conformation traits

Answer 17

Foot angle
Rear legs rear view
Rear legs side view
Udder depth
Teat placement
Rear udder width and height
Udder support
Fore udder attachment
Teat length
Rump angle
Rump width
Chest width
Body depth
Bone quality
Strength