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The Sundance Times
Sundance, Wyoming
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May 23, 1957     The Sundance Times
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May 23, 1957
 

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Inheritance in Cattle and Sheep For centuries, animal breeders attempting to produce superior animals have met with only var- iable degrees of success. The fact that their goal was not always com- pletely attained indicates that the methods used by these breeders were not generally the most effi- cient or constructive. No way has yet been found that can be pointed out as a sure method to produce superior stock success- fully, but a better understanding of the mechanism of inheritance can now be had by the breeder to suggest more promising routes. GENETICS is a relatively new science concerned with the mech. anism of inheritance. Since it is new, investigators are continually making new discoveries which add materially to information already at our disposal. There are, how- ever, certain basic principles which can be used as a foundation upon which to build further. These basic principles, or foundations, will be discussed in some detail. To the beginner, perhaps one of the most formidable obstacles to an understanding of genetics is the vocabulary. New words and new meanings for old words may make reading difficult and confus- ing. A little usage will make these Words much more famiiiar; in a very short time they can be handl- ed with ease. Mechanics of Inheritance Every animal, regardless of size, is composed of thousands of micro- seopic "building stones" called CELLS. The individual cells dif- fer within each animal, so that a bone cell is not the same size or shape as a muscle cell or a brain cell. However, all cells do have some characterisitcs in common. Each cell is enclosed by a CELL WALL which keeps it separate from the adjacent cells. Within the cell wall is found a liquid ma- terial called CYTOPLASM which contains minute food particles and other inclusions. Also inside of the cell is found another small body enclosed by a membrane. This is called the NUCLEUS and is the "heart" and the "brain" of the cell. In the nucleus of the cell are small, rod-shaped bbjects which are of primary interest in the study of heredlfy. These minute objects, called CHROMOSOMES, are com- posed of a series of sub-microsco- pic particles called GENES. Thus the chromosome may be thought of as a string of beads, and each bead represents a gene. The genes are the actual determiners of the here- ditary characteristics of an animal. Thus the genes are an important influence in such factors as color, size, conformation, temperament, gaining ability, and many others. The chromosomes, which occur in pairs, are alike in all of the cells in the animal. The members of each pair of chromosomes are alike in size and shape but differ from other pairs. The number of chromosomes present is character. istic of a species: cattle have 30 pairs, sheep 27 pairs. Although the members of ,~ chromosome pair appear the same, they may contain genes which have different effects. That is, one mem- ber of the pair may contain a gene for horns but the other chromo- some could carry instead the gene for the poll characteristic. If this condition exists the animal will be polled, since that gene is DOM- INANT to the gene for horns. The horn gene is then called RECES- SIVE. Not all characters are due to single genes, but, regardless of the number of genes concerned, some will be dominant while others will be recessive. The animal thus has many thousands of pairs of genes, some of which are alike but many are different. When a pair of genes carried by an animal are identical, they are called HOMOZYGOUS; if the genes are different the condition is call. ed HETEROZYGOUS. Thus an animal that has AA is homozygous for gene A, while an animal that is Aa is hetrozygous for this fac- tor. The ~Production of Sperm and Eggs Every animal is the resfilt of the union of "a sperm and an egg. Each sperm produced by a male animal carries one member of each pair of chromosomes. Each egg pro- duced by the female also contains but one member of each of the same chromosome pairs. Thus, when the sperm and the egg are united, a full complement of chro- mosomes is again present. One-half of the chromosomes present in the new individual come from the male parent, the other half from the female parent. The particular member of the chromosome pairs which is present in the sperm or egg is entirely a matter of chance. There is an equal probability of either member of any chromosome pair from one parent uniting with either member of the chromosome pair of the other parent. When the inheritance of a char- acter is known, that character is usually given a symbol to repre- sent it. Usually one or two letters are used and the letters may come from the character they symbolize. For example, the black color of the Angus is dominant to the red color of the Angus or Hereford. The gene for black is designated as B while the gene for red is designat- ed as b. Thus an Angus that car- ries both genes for black is BB while a Hereford is bb. If two such animals are mated, the offspr;ng will have one B gene from the Angus parent and one b gene from the tIereford parent. It is, there- fore, Bb and appears black. It happents, however, that the Here- ford pattern is partially dominant to the Angus pattern. ; The off- spring then has a white head like the Hereford parent. A black Angus (BB) is mated to a red Hereford (bb). The F1, or first generation, is black because the gene for black (B) is domin- ant to the gene for red (b). When F1 males are mated to F1 ;females (Bb x Bb), a definite color ratio can be expected in the next gen- eration. Two kinds of eggs are produced, one-half carrying the gene for black and one-half the gene for red. The same is true of the sperm. If the sperm with B gene fertilizes an egg with the B gene, this offspring is black, and since it contains only the B gene it will breed true for black. If the sperm carrying the gene for red (b) fertilizes the egg with the gene for black (B), the individual appears black, but will not breed true for black since it also con- tains the gene for red. If the sperm carrying B fertilizes the egg carrying the b gene the result is black. If the sperm with the b gene fertilizes the egg with the b gene, this individual is red in ap- pearance and will produce eggs or sperm with only the b gene. Thus, from the F1 matings, three4ourths of the individuals would appear black and one-f~urth red. Actually, Weekend guests at the however, 25 percent of the animals Harvey home were their will appear black and will breed family, Mr. and Mrs. true for black, 25 percent will vey and Mike of Casper. Mr. and Mrs. Harvey carry only the gene for red, and Miss Wynn Hooper and 50 percent will be black but will tIooper shopped in Spearfish carry the gene for red. day. . ( ET TtlAT "BIRD ! ~..then get yoursel! line bourbon._ ,Ask for and tell the world you know great' straight Ke OLD HERMITAGE BRAND OLD HERMITAGE COMPANY, LOUISVILLE, KY., DISTRIBUTED BY ]~RODUCTS COMPANY, KENTUCKY STRAIGHT BOURBON WHISKEY, More ood, Golden Valley Orange Juice Dreher's 4 • • • • • 46 oz. can • • 22 oz. jar Q • Q • • • • • iii Giant Glim Liquid Detergent Two 22-Oz. Cans - - 89’ 4 • • ill Red Sour Pitted 808 can for Fresh Frozen • Q • s-35’ 10 oz. pkg. • • • • ’# • • • • • Spearfish, S. D. Men's and Boys' for dress and work John B. Stetson Other Brands Men's $1.49 to $2.98 Boys' 59c to $1.98 \ J Sundanee "Everything to Wear" II