Section 10— Developmental Genetics 



10.48. Lethal Micromelia in the White Pekin Duck. 



William J. Ash (Cornell, U.S.A.). 



Routine inspection of unhatched pedigreed 

 eggs uncovered a lethal syndrome in the White 

 Pekin duck. Affected embryos appear smaller 

 than their normal sibs. Most conspicuous is the 

 marked shortening of the extremities. Shortening 

 of the upper mandible is observed in some but 

 not all birds. Feathering is greatly retarded, and 

 many embryos appear naked. Feathers which 

 develop often take on a "wormy" appearance. 

 Subcutaneous edema is conspicuous in the 

 cervical region. 



Affected embryos survive to terminal stages of 

 incubation. Some pip their shells, but none has 

 ever hatched. 



Histological examination of the long bones 

 reveals irregular cartilagineous architecture at the 

 epiphyses. The orderly transformation of young 

 discoidal chondrocytes into mature ovoid ones is 

 absent. Ossification does occur, but it is limited 

 presumably by the aberrant cartilagineous model 

 which precedes it. 



Matings of phenotypically normal carriers indic- 

 ate that this syndrome is an autosomal recessive 

 obligate lethal mutation. 



cribed by Eker in 1954 ( x ) and a preliminary 

 report on the genetic aspect has been published! 2 ). 



10.49. Dominant Renal Adenomas in the Rat. 



Jeanne Mossige and Reidar Eker (Monte- 

 bello, Norway). 



The renal adenomas which occurred in an 

 inbred strain of Wistar rats at this laboratory 

 have proved to be due to a dominant gene with 

 complete penetrance. No homozygote has been 

 found. 



The earliest macroscopically detectible tumors 

 have been found at about 3 months, but they 

 may appear first at the age of one year or later. 

 Their development has been followed from 

 early stages in serial sections. They begin as 

 small, cystic tubules and develop into cystic, 

 cysto-papillary or solid tumors and are almost 

 always bilateral. Most of them are well limited 

 without cellular atypia, but many exhibit 

 atypical nuclei and invasive growth in the kidney. 

 Only a few, however, have metastasized, to the 

 liver and lungs, proving malignancy. In humans 

 they would be diagnosed as renal carcinoma. 



They develop earlier in males than in females 

 and usually appear in the left kidney earlier than 

 in the right. Various experimental series are 

 being run to test factors which might influence 

 the development of the tumors. 



The pathology of the tumors has been des- 



1. Acta Path, et Microbiol. Scand. 34, 554. 



2. Eker and Mossige, Nature 189, 858, 1961. 



10.50. Periodical Hypotrichosis in Mice. N. Kobo- 

 zieff and N. A. Pomriaskinsky-Kobozieff 

 (Maisons Alfort, France) 



Periodical hypotrichosis in mice is a recessive 

 mutation with incomplete penetrance. The 

 phenotypical manifestation takes place between 

 the 16th and 21st day after birth and may 

 reappear at more or less frequent intervals. 



The genetical analysis of the normal descen- 

 dants of two abnormal parents (penetrance 

 30 per cent), shows that they behave genetically 

 as abnormal animals. 



When crossed to abnormal, penetrance among 

 the offspring is lower (24 per cent), when crossed 

 inter se it is only 20 per cent, and in the F-2 it 

 drops to 10 per cent 



The phenotype is variable, there are 6 classes : 



— little loss of hairs, hair sparse on the whole 

 or part of the body (Type I), 



— loss of hair in the scapular region (Type II), 



— loss of hair on the whole thoracic region 

 (Type III), 



- loss of hair as far as the sacral region, hairs 

 remain only on the head and the base of the 

 tail (Type V), 



— loss of hair on the thighs and later than 

 normally (Type VI). 



The gestation factor is important : the highest 

 frequency of abnormal is seen in the first litter. 

 It is lower in the second and inexistent in the 

 others litters. 



The seasonal factor is also interfering: during 

 the whole year we observe litters comprising 

 normal and abnormal subjects but it has been 

 noticed that 54 per cent of the litters containing 

 abnormal mice appear in July- August; whereas 

 in the same period we have found 28 per cent of 

 the litters to consist exclusively of normals. 

 This shows clearly that the highest frequency of 

 litters with abnormal subjects is observed in 

 July-August. 



10.51. Response of Polycythemic WW V Anemic Mice 

 to Erythropoietin. Margaret W. Thompson, 

 Elizabeth S. Russell, and Eleanor C. Mc- 

 Farland (Edmonton, Canada). 



The hematopoietic defect in WW V anemic mice 



185 



