Animal genetics / Frederick B. Hutt.

  • Frederick Hutt
Date:
[1964]
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Animal genetics / Frederick B. Hutt. Source: Wellcome Collection.

    519/578 page 497
    HEREDITY IN DOMESTIC ANIMALS 497 range in the interests of people who breed domestic animals, or mul¬ tiply their numbers, or minister to their welfare. Few of us alone are likely to breed sapphire minks, Manx cats, and lambs with halo- hairs, but, whatever our pet species, and whether we prefer to look at whole animals, or only those parts of them that can be put in a test tube or under a microscope, each has a chance to transfer some mite of knowledge about the genes of domestic animals from the realm of the unknown to that of science. PROBLEMS 21—1. Wriedt and Möhr found that four sires of amputated calves mated to daughters of other carrier bulls yielded 13 amputated calves among 115. Was that in accord with expectations, or not? 21—2. From matings infer se of cats heterozygous for taillessness, Todd obtained 63 tailless and 27 tailed kittens. Can you tell from these figures whether or not homozygosity for taillessness is lethal? 21—3. If further data should confirm indications that most genetically tail¬ less cats are heterozygotes, how would you advise breeders of Manx cats to select, in order to reduce the proportion of unwanted stumpies, or bob-tailed cats? 21—4. Referring to Table 21-1, what size of litter would be expected from the Manx X Manx matings if the gene for taillessness were lethal, and if the normal, average litter size for cats were 3.88? 21—5. Does your answer affect your answer to Problem 21-2? 21—6. Sooner or later, some sheep breeder will find another mutant of the Ancon type, and will want to breed a flock of them. If he should appeal to you for advice, how would you advise him to proceed? Remember that close inbreeding must be avoided at early stages if reproduction is to be maintained. 21—7. For the situation of Problem 21-6 would you rather have the original mutant a ram or a ewe? 21—8. After the breeder of the new Ancons has a flock large enough to permit some selection among them, he will want to reduce the proportion so crippled by their short bent legs that they have difficulty in walking. How should he select to that end? 21—9. Do you know any breed of domestic animals in which this trick has been done? There is one; it begins and ends with d. 21-10. If a breeder of rex cats, worried a little about inbreeding in her stock of them, wants to introduce blood of rexes that originated in another country, by what matings could she determine whether the two kinds are genetically identical or different, and what results could she expect in first crosses, backcrosses, and F2 generations if the two mutations are (a) identical? (b) Not at the same locus? 21-11. Dry was able to identify his NN hairy Romneys at birth by their halo-hairs. Do you know any other cases in domestic animals in which those
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