2. Enterprise:Animal Science Unit:Basic Genetics Factor Information needed I. Intro.A. The use of genetics to improve animals can not be overlooked by producers. B. There are many career opportunities in this area. II. Genetic Basics A. Differences in animals are due to genetics or environment. 1. Phenotype- physical appearance of the animal.

3. 2. Genotype- genetic makeup of an animal. a. environment does not affect genotype, only phenotype. B. Gene transfer- parents pass on their characteristics to an offspring, 1/2 from each, through chromosomes. 1. Made of up DNA strands. 2. a gene is a small portion of the DNA and controls one characteristic. 3. RNA carries the DNA message to the rest of the cell.

4. 4. differentiation [The process in which the cells become muscles, bone, etc] occurs from cells which are genetically the same. C. a pair of genes which controls a characteristic are called an allele. 1. homozygous pair- when both genes are the same. (both polled PP) 2. heterozygous pair- genes are different. ( one horned, one polled hP) a. dominant gene will determine look of offspring. ( hP will look polled )

5. 3. To show horns the pair must be homozygous recessive (hh). 4. Because of heterozygous dominant genes the look (phenotype) of a parent will not always be the same in the offspring. 5. Some gene pairs have codominance, usually leading to a blending of traits a. white(W) of Charolais crossed with black(B) of Angus lead to gray color (WB gene pair).

6. 6. There is also gene pair interaction that can effect overall phenotype (epistasis). 7. Additive expression is when several pairs work together to form a trait. III. Sex Deter- mina- tion A. The sex chromosomes determine the sex of the offspring. 1. The female is XX. 2. The male is XY. 3. The male sex cells chromosome will determine the sex of the offspring.

7. IV. Using Genet ics A. Using phenotype only in selecting breeding animals can lead to disappointment. 1. However for genetics to be useful there must be high heritability. a. a measure of how much of the trait is passed on by genes and not environment. B. The use of performance data is very useful in selecting livestock. 1. Indexes- comparison of animals within a group, usually based on 100.

8. a. Weaning weight, yearling weight, and birth weight can all be indexed. 2. Mothering ability measures a. shows mothers ability to produce milk, which helps offspring grow. b. MPPA- most probable producing ability is used in beef cattle. c. Sow Index in pigs and Ewe Index in sheep also show mothering ability. 3. Estimated Breeding Values are used in cattle to measure performance- based upon own performance and 1/2 siblings.

9. 4. EPDs (Expected Progeny Difference) has gained a lot of popularity for selecting bulls. It measures against reference bulls within a breed. 5. Linear evaluation is used by dairy producers in selecting AI bulls to improve weaknesses in each cow. a. each cow has approx. 17 traits measured and given a score of 1 to 50. b. bulls can then be selected that score high in those specific trait areas. c. offspring should be better than mom.