Paper One: MACVSc



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Australian College of Veterinary Scientists

Membership examination

June/July 2008

Animal Breeding and Genetics

Paper 1

Perusal time: fifteen (15) minutes

Time allowed: two (2) hours after perusal

Answer four (4) from the six (6) questions only

All questions are of equal value

Subsections of questions are of equal value unless stated otherwise

Paper 1: Animal breeding and genetics

Answer four (4) from the six (6) questions only.

1. Briefly describe the meaning of each of the following terms:

– karyotype

– meiosis

– heterozygous

– locus

– autosome

– epistasis.

2. The polymerase chain reaction (PCR) is an in-vitro process that exploits certain characteristics of deoxyribonucleic acid (DNA). Describe the PCR process and how it can be used to detect the presence of particular sequences of DNA with great sensitivity. In your answer, describe the characteristics of DNA that make this reaction possible.

3. ‘The frequency of a particular allele in a population of offspring is expected to equal the frequency of the same allele in the parent population, provided mating occurs at random with respect to that locus, and there is no selection at that locus’. This statement is an example of the Hardy-Weinberg law.

Discuss this principle in relation to the increase in frequency of anthelmintic-resistance alleles in successive generations of nematode parasites of domestic animals when the host species is repeatedly and frequently treated with anthelmintic drugs. In relation to the same principle, explain the circumstances under which rotation of anthelmintics is expected to be useful in delaying the development of resistance.

Continued over page

4. Inbreeding occurs when two related individuals are mated. In most farm animal breeding programs, some degree of inbreeding is common.

The risk of inbreeding and the degree of inbreeding within an animal population can be estimated by calculating the effective population size (Ne), calculated as:

Ne = 4.s.d.L/(s+d)

where

s is the number of new sires entering the population per year

d is the number of new dams entering the population each year

L is the average age of the male and female parents when their offspring are born.

The increase in inbreeding per year in a population is approximately equal to 1/(2.Ne.L).

Consider a closed herd of cattle that consists of 1000 cows. No bulls are purchased from outside the herd. In relation to the formulas given above, discuss the rate of inbreeding in the herd and describe what factors might increase the rate significantly, and what strategies might be used to minimise the rate of inbreeding. Include in your answer the impact of the types of management strategies sometimes practised in cattle-breeding programs, such as artificial insemination.

5. The term ‘estimated breeding value’ (EBV) is frequently used in farm animal breeding programs in Australia. EBVs are calculated for individual animals and published to provide guidance to breeders and buyers of animals. EBVs are often published with associated values for ‘accuracy’.

For example, one bull (Bull A) may be given an EBV for a trait of +5, with an accuracy of 70%, while another bull (Bull B) may be given an EBV for the same trait of +3, with an accuracy of 99%.

Describe what is meant by the terms EBV and accuracy, and illustrate your understanding of these terms by discussing the relative merits of Bulls A and B.

Continued over page

6. The response to selection of a population of animals is proportional to the selection intensity applied.

Using a breed or species of domestic animal with which you are familiar, briefly describe a genetic selection program and discuss how the rate of genetic progress can be slowed or accelerated by varying the selection intensity. Demonstrate in your answer that you clearly understand all the following terms:

– selection intensity

– selection differential

– heritability

– genetic variance.

End of paper

[pic]

Australian College of Veterinary Scientists

Membership Examination

June/July 2008

Animal Breeding and Genetics

Paper 2

Perusal time: fifteen (15) minutes

Time allowed: two (2) hours after perusal

Answer all four (4) questions

All questions are of equal value

Subsections of questions are of equal value unless stated otherwise

Paper 2: Animal breeding and genetics

Answer all four (4) questions.

1. Select an animal industry of your choice and describe how crossbreeding is used, or could be used, to increase the productivity of the farmed animals in that industry. Include in your answer an explanation of why the strategy is or could be successful.

2. The mathematical technique of best linear unbiased prediction (BLUP) is now used widely in the animal industries of Australia and other developed countries to provide genetic evaluation of animals and to estimate rates of genetic change in those populations.

Select one (1) industry that has a genetic evaluation program based on BLUP technology, and describe the processes involved in producing information for breeders, starting with the mechanisms for data collection from breeders. It is not necessary to describe what BLUP is, but you must describe in general terms what it does. Your answer should also address the mechanisms involved in the flow of ‘raw’ information from breeders to a central processing bureau and as ‘processed’ information back to the users of the information.

3. Using as an example an industry of your choice, describe how modern molecular genetic techniques are being used to identify individuals with particular beneficial or deleterious traits.

4. In early 2008, the United States Food and Drug Administration (FDA) declared there is no reason that cloned livestock and their offspring cannot be used for food. The ruling came despite opposition from some consumer groups.

Give your views about this decision by the FDA and, using your understanding of the science of genetics, argue whether you believe this decision to be correct or incorrect.

End of paper

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