File:The mating and breeding of poultry (1920) (14779360044).jpg

Identifier: matingbreedingof00lamo (find matches)
Title: The mating and breeding of poultry
Year: 1920 (1920s)
Authors: Lamon, Harry M. (Harry Miles), 1872- Slocum, Rob R. (Rob Roy), 1883-
Subjects: Poultry
Publisher: New York, Orange Judd Co.
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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ity, but it isdifficult to demonstrate except where the number of units issmall, and hence is in most cases of little more than theoreti-cal importance. Certain cases of simple Mendelian inheritance frequentlycome under the eye of the poultryman who makes crosses.A^n illustration, let us consider what happens when a fowlfrom a strain which produces rose combs only is mated witha single comb, which, as breeders know, breeds true. Theoffspring all have rose combs. Rose comb is said to bedominant over single comb. The crossbreds breed verydifferently, however, from their rose comb parent. Theybreed as if half of their germ cells (spermatozoa in the male,eggs in the females) transmit ros^^omb_only, while halftransmit single comb only. This is easily seen on crossingthem with single combs, in which case they produce 50 percent rose combs and 50 per cent single combs. The rosecombs of this generation, when crossed with single combsagain, produce 50 per cent rose combs and 50 per cent single
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16 THE MATING AND BREEDING OF TOULTRY combs, although the chicks are seven-eighths blood singlecomb. This system of mating can be carried on indefinitely,the rose comb chicks always producing 50 per cent rosecombs and 50 per cent single combs, regardless of theamount of blood from single comb strains. When two ofthese crossbred rose combs of any generation are mated witheach other, 25 per cent of the chicks will have single combs.The reason is easily seen. Half of the eggs transmit singlecomb and half of these, or one-quarter of all eggs, will, bychance, be fertilized by spermatozoa which transmit singlecomb, the result being that 25 per cent of the chicks fail toget rose comb from either parent and so are single combs.Conversely, it is easy to see that there will be another 25per cent of the chicks which get rose comb from both parentsand will breed like pure rose combs, although in blood theymay be almost wholly of a single comb strain. The remain-ing 50 per cent of the chicks get r

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