Íslenskar landbúnaðarrannsóknir - 01.03.1970, Síða 136

134 ÍSLENZKAR LANDBÚNAÐARRANNSÓKNIR
Chapter IV.
Collection of data from flock books
A. Description of flocks ................................................... 33
B. Items of information collected .......................................... 34
C. Preparation of records for punching ..................................... 35
D. Transfer of cards to magnetic tape .......................................... 37
E. Selection of cards of interest .............................................. 37
Chapter V.
Observed segregation at the A-locus ................................................... 38
A. Observed colours ............................................................ 38
B. Unexpected colours ........................................................ 38
1. Individual cases ................................................... 39
2. Discussion of unexpected colours ................................... 48
3. Contemporary twins by two different sires .......................... 49
4. Unexpected colours produced by a lightgrey ram ..................... 49
Chapter VI.
Analysis of observed segregation at the A-locus ....................................... 54
A. Estimation of allele parameters ............................................. 55
B. Subnormal variation in segregation ratios ................................... 63
C. Effect of sex of lamb and type of birth on segregation ratios ............... 67
D. Effect of colour on fertilty ................................................ 67
E. Effect of colour genotype of parents on lamb survival ...................... 76
F. Sex and colour ratios among singles and twins in known matings .............. 76
G. Selective fertilization and entbryonic mortality ............................ 79
H. Relation between score for tan colour and homozygosity for the Ai-allele 85
I. Relation between score for grey colour and homozygosity for the A2-allele 87
J. Selective fertilization involving alleles A^ and Ao ......................... 90
K. Gene frequencies at the A-locus ............................................. 92
Chapter VII.
Analysis of segregation at loci B and S and linkage between colour loci ............... 95
A. Segregation at the B-Iocus .................................................. 95
B. Segregation at the S-locus .................................................. 95
C. Effect of loci B and S on iertility ......................................... 99
D. Linkage between colour loci ................................................. 99
Chapter VIII.
Discussion of inheritance of colours in sheep ......................................... 101
A. Recessive black vs. recessive brown pigment ................................ 101
B. Dominant black ............................................................. 102
C. Dominant brown ............................................................. 103
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