Table 2. Chromosomal locations of quantitative trait loci and single nucleotide polymorphisms associated with twinning rate and ovulation rate in cattle.
| Trait | Chromosome and approximate location within chromosome (Mb) | Population | Positional candidate genes (chromosome) | Ref. |
|---|---|---|---|---|
| Ovulation rate | 7 (40) and 23 (27) | MARC twinner | CYP21 (23) | Blattman et al., 1996 |
| Twinning rate | 5 (64), 7 (108), 12 (10) and 23 (26) | Norwegian cattle | IGF1 (5), CYP21 (23) |
Lien et al., 2000; Meuwissen et al., 2002 |
| Ovulation rate | 5 (46) | MARC twinner | Kappes et al., 2000; Allan et al., 2009 | |
| Twinning rate | 5 (68) | US Holstein | IGF1 (5) |
Cruickshank et al., 2004; Kim et al., 2009b |
| Twinning rate | 8 (108), 10 (26) and 14 (51) | US Holstein | Cobanoglu et al., 2005 | |
| Ovulation rate | 14 (61) | MARC twinner | Gonda et al., 2004 | |
| Ovulation rate | 7 (22), 10 (75) and 19 (42) | MARC twinner | AMH (7), ESR2 (10), IGFBP4(19) |
Arias and Kirkpatrick, 2004 |
| Twinning rate | 4 (44), 5 (67), 6 (8, 44), 7 (68, 76), 8 (58), 9 (34), 11 (47), 14 (21, 38), 15 (23), 23 (51), and 28 (9) |
US Holstein | IGF1 (5) | Kim et al., 2009a; Bierman et al., 2010 |
| Twinning rate | 6 (51), 7 (19), 23 (27) | AMH (7), CYP21 (23) |
Weller et al., 2008 | |
| Twinning rate | 24 (40) | Italian Maremmana | Moioli et al., 2017 |