Phenotypes

The causative mutation for this disorder was discovered via the candidate gene approach. Tassi et al. (1984) reported a 10-15-fold decrease in the concentration of TG mRNA in affected cattle; Ricketts et al. (1985) reported the use of S1 nuclease assays and electron microscopy to narrow down the location of the mutation to the junction of exon 9 and intron 9; and Ricketts et al. (1987) reported the use of cloning and sequencing of genomic DNA ...

As reported by Kadri et al. (2014), one of the genes in the deletion (see Mapping section), namely RNASEH2B, is "known to cause embryonic lethality when knocked-out in the mouse". Subsequent investigations confirmed that this deletion is a recessive embryonic lethal in cattle but "is associated with a positive effect on milk yield and composition", which results in selection favouring heterozygotes (balancing selection), thereby maintaining th...

Jacinto et al. (2022): "A trio whole-genome sequencing approach was carried out and identified a private homozygous missense variant in LAMB1 affecting a conserved residue (p.Arg668Cys)."

Maple Syrup Urine Disease (MSUD) is an autosomal recessive defect reported in Poll Hereford (PH) and Poll Shorthorn (PS) calves (Harper et al., 1986; Healy et al., 1992). The clinical, biochemical and pathological characters of the disease are identical in the two breeds of cattle, and are characterised by the rapid onset of progressive neurological disease, resulting in death within a few days of birth. The disease is caused by a deficiency o...

Besser et al. (1990) reported a congenital syndrome of long, thin limbs, severe joint and tendon laxity, microspherophakia, ectopia lentis, heart murmurs and aortic dilatation in 7 calves, where all sired by a single phenotypically normal bull suspected of germline mosaicism for a new mutation resulting in this disease. One of the calves died with ruptured aorta at age 16 months. Histopathologic and electron microscopic studies of the aortic m...