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Ansc 241: Quantitative Genetics And Animal Breeding Question Paper
Ansc 241: Quantitative Genetics And Animal Breeding
Course:Bachelor Of Science In Animal Science
Institution: Chuka University question papers
Exam Year:2013
UNIVERSITY EXAMINATIONS
EXAMINATION FOR THE AWARD OF DEGREE OF
BACHELOR OF SCIENCE (ANIMAL SCIENCE)
ANSC 241: QUANTITATIVE GENETICS AND ANIMAL BREEDING
STREAMS: BSC (ANSC) &BSC (AGED) TIME: 2 HOURS
DAY/DATE: WEDNESDAY 7/8/2013 8.30 AM – 11.30 AM
INSTRUCTIONS:
This examination has two sections (A and B)
Answer all Questions in Section A and any Three Questions in Section B
Section A (Answer all Questions. Total Marks = 30)
1. Define the following terms:
(a) Selection
(b) Phenotype
(c) Breeding value
(d) Genotypic value
(e) Mating [10 marks]
2. The proportion of the phenotypic variance that is due to additive genetic variance is referred to as the heritability. Heritability can also be defined as the regression of the breeding values on the phenotypic variance. Prove that this statement is true.
[5 marks]
3. (a) The population mean for an important trait in cattle is 8000kg. The heritability of the trait was estimated to be 0.3. A particular dam has a phenotypic value of 9000 kg for this trait. Calculate the breeding value for this animal. [5 marks]
(b) What is the accuracy of breeding value estimated in 3(a) above? [2 marks]
4. Complete the following model:
A_0= +1/2 A_D+ E_0 [2 marks]
5. Distinguish between the following:
(a) Additive genetic relationship and inbreeding coefficient
(b) Selection index and breeding goal. [6 marks]
Section B (Answer Three Questions. Each Question is 14 Marks. Total Marks = 42
6. The following is the pedigree for the bull “Spark”:
(a) Calculate the additive genetic relationship between Stallion and Kim [5 marks]
(b) Calculate the inbreeding coefficient of Spark [5 marks]
(c) Spark was mated with a dam Kathure whose estimated breeding value for milk production is +80 kg. The estimated breeding value for milk production of Spark is +110 kg. The average milk production of the farm is 8000kg. Calculate the expected milk production of their daughter Wanja. [4 marks]
7. Double muscling is a condition where animals show a form of muscle hypertrophy. The condition is genetically determined by single locus mh. Animals that are homozygous dominant, i.e. mh/mh at the locus show the hypertrophy. By use of genetic mapping the frequency of the mh allele was determined to be 0.60 in a population of 10,000 animals.
(a) What is the frequency of heterozygotes and homozygotes assuming that this population is in Hardy Weinberg equilibrium? [5 marks]
(b) Based on DNA typing it is estimated that there are 8,000 heterozygote mh/+ individuals in the population. How many homozygote mh/mh and homozygous (+/+) individuals are there in this population? [5 marks]
(c) This locus influences the birth weight of new borns. The genotypic values for the locus are as follows:
mh/mh 16gms
mh/+ 14gms
+/+ 10gms
Calculate:
(i) The genetic effect, a and the dominance deviation, d
(ii) The population mean (assume Hardy-Weinberg equilibrium)
8. (a) Define the term selection differential (s) [2 marks]
(b) The mean growth rate from birth to weaning for the pig population is 800 gm/day. In a population of 20,000 dams 200 dams were selected as parents. The mean of the selected proportion was determined to be 980 gm/day. Calculate the selection differential for the selected proportion. [2 marks]
(c) If the phenotypic standard deviation for growth rate from birth to weaning is 1000 gm. Calculate the selection intensity for the selected proportion. [2 marks]
(d) If in the above population of pigs the following parameters were determined; accuracy of selection was 0.87, additive standard deviation was 200 gm and the generation interval was 0.5 years. What is the expected response to selection per year? [4 marks]
(f) Breeding values of sires were estimated using phenotypic records of their progeny. In the breeding program each sire had 20 offspring records for evaluation. If the heritability for the trait growth rate is 0.25, determine the accuracy of selection of the sires. [4 marks]
9. In a dairy cattle breeding program, the breeding objective is to improve milk production. Bulls are selected based on 100 progeny performance records and dams are selected based on their own first lactation performance. The heritability for the trait milk production is estimated to be 0.3. Generation interval for bulls is 5 years and for the cows is 3 years. The additive standard deviation for milk production is 500 kg. Each generation 100 sires and 2000 dams are evaluated, out of which 10 sires and 1400 dams are selected.
(a) Determine the selection intensity for both sires and dams [3 marks]
(b) Determine the accuracy of selection for both sexes. [3 marks]
(c) Calculate the response to selection per generation. [5 marks]
(d) Calculate the response to selection per year. Comment on your answer.
[3 marks]
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