practical genetics SDL

Question 1

what is meant by the term hip dysplasia

Answer 1

hip joint is abnormally formed. instead of fitting snuggly into the socket the femoral head is loose which can allow it to move out of place or become misaligned

Question 2

what is meant by the term selecting against a gene

Answer 2

refers to the practice of breed or genetic selection aimed at reducing ot eliminating a specific undesitable gene or trait from a population.
- involves identifying and breeding individuals that do not carry or express a particular gene associated with an undesirable trait or condition

Question 3

what is meant by the term selection co-efficient

Answer 3

The selection coefficient is a measure of the relative fitness reduction of individuals with a particular allele or genotype compared to the most fit individuals in a population. It quantifies the strength of selection against or for specific traits and is used to predict changes in allele frequencies due to natural or artificial selection.

Question 4

what is meant by the term heritability

Answer 4

Heritability measures the proportion of trait variation due to genetic factors within a population. It helps predict the potential effectiveness of genetic selection and breeding strategies, though it is specific to the population and environment where it is assessed.

Question 5

what is meant by the term liability

Answer 5

Liability in genetics refers to the predisposition or risk of developing a particular condition based on an individual’s genetic and environmental factors. It is a measure of how likely it is that a person will exhibit a certain genetic trait or disorder, influenced by both genetic predisposition and external environmental conditions.

Question 6

i. Describe the mode of inheritance of HD

Answer 6

Hip dysplasia has a multifactorial mode of inheritance involving multiple genetic factors and environmental influences. It does not follow a simple Mendelian pattern but is influenced by the combined effects of several genes and external conditions. Effective management involves genetic testing, selective breeding, and preventive measures to reduce the risk and impact of the condition.

Question 7

ii. List 4 non-genetic factors which contribute to the development of HD

Answer 7

• nutrition
• exercise and activity levels
• body weight and obesity
• environemental (flooring and surfaces)

Question 8

iii. What percentage of dogs greater than 1 year old are affected by osteoarthritis?

Answer 8

20-30%

Question 9

v. What is the estimated heritability of HD?

Answer 9

The heritability of hip dysplasia is estimated to be between 20% and 50%, indicating that genetic factors play a significant role in the risk of developing the condition. This estimate varies among different breeds and populations and is used to inform breeding practices and genetic research.

Question 10

vi. What is meant by a biphasic distribution?

Answer 10

A biphasic distribution is a statistical distribution characterized by two distinct peaks, indicating the presence of two separate groups or categories within the data. This type of distribution is used to analyze and interpret complex data sets in various fields, including genetics and medicine, to uncover underlying subpopulations or factors.

Question 11

ii. From what you know about the mode of inheritance of HD, which of the two genomic investigations would you consider the most useful and why?

Answer 11

genome wide association studies due to their ability to handle the complexity and multifactorial nature of the condition. GWAS can identify specific genetic variants associated with hip dysplasia, providing valuable insights for predicting, managing, and breeding for reduced incidence of the condition.

as opposed to genetic linkage studies (focus on single genes)

Question 12

a. What is the minimum age at which a dog can have its ‘Hips Scored’?

Answer 12

12 months

Question 13

b. What considerations should be made by a veterinary practice when arranging to ‘Hip score’ a dog for a client?

Answer 13

veterinary practices should consider the dog’s age and health, ensure proper preparation and equipment use, adhere to the protocols of scoring organizations, manage post-procedure care, communicate costs and results effectively, and maintain thorough documentation. These considerations help ensure accurate results and a positive experience for both the dog and its owner.

Question 14

c. Describe briefly how the submitted radiograph is scored

Answer 14

• quality check of rad
• assess landmarks
• joint conformation (coxofemoral joint, hip socket depth, bone changes)
• BVA provides numerical score, OFA excellent - poor

Question 15

d. Which 3 breeds of dog have
i. The highest BMS
ii. The lowest BMS

Answer 15

highest: german shepherd, laborador retriever, rottweiler
lowest: greyhound, whippet, border collie

Question 16

3. What is meant by the term “genetic index” ?

Answer 16

A genetic index is a numerical value that summarizes an animal’s genetic potential for specific traits, used to guide breeding decisions. It combines information from genetic markers, performance data, and pedigree information to evaluate and select animals with desirable traits. Genetic indices are essential tools in modern breeding programs, helping to improve the genetic quality of livestock across various traits.

Question 17

4. Explain two advantages of using £PLI (Profitable Lifetime Index) to select the right bulls for your breeding programme:

Answer 17

1. Comprehensive Profitability Assessment
   Advantage:

Holistic Evaluation: The £PLI provides a comprehensive measure of a bull’s genetic contribution to the profitability of its offspring over their lifetime. It combines various traits into a single index, including milk yield, fat and protein content, fertility, longevity, and health traits.
Benefits:

Informed Decision-Making: By considering multiple factors that influence overall profitability, the £PLI helps breeders make informed decisions about which bulls are likely to produce high-performing, profitable offspring.
Focus on Profitability: Unlike indices that focus solely on production traits or specific health aspects, £PLI integrates these factors to give a more balanced view of a bull’s genetic contribution to the farm’s profitability.
2. Long-Term Economic Benefits
Advantage:

Lifetime Profitability: The £PLI is designed to predict the lifetime profitability of offspring, not just short-term production gains. This means it helps in selecting bulls that will contribute to long-term economic success on the farm.
Benefits:

Sustainable Breeding: By focusing on traits that impact lifetime performance and longevity, £PLI supports sustainable breeding practices that enhance the overall efficiency and profitability of the herd.
Cost-Effective Management: Bulls with a high £PLI are likely to produce daughters with better fertility, lower veterinary costs, and longer productive lives, resulting in a more cost-effective and profitable dairy operation.