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ian
May 05, 2022
In Pedigree Q&A
I'm posting here response from Dr. Matt Hegarty of IBERS, University of Aberystwyth, to my post of 4th Dec.2021on dam of lines:- "I've attached a couple of PowerPoint figures showing how matrilines could be disproportionately represented over time within populations - especially with the heavy use of bull lines and line breeding: - "Dam lines are of importance in animal breeding as much of the selection is performed on the sires, which only carry a single copy of the X chromosome inherited from their mother. A bull's sons will not inherit his X chromosome, so any contribution it makes to the bull's EBV will not be passed to his male offspring (whereas his daughters will have 50% of his EBV and 50% of the dam's, as for all the other chromosomes). Over time, this can lead to predominance of certain matrilines if a limited number of sires is used within a population (or line breeding occurs). "Many important traits to do with sexual development are carried by genes present on the X chromosome, particularly to do with fertility in both males (sperm motility and scrotal circumference, for example) and females (eg: age at first calving, ovulation rate, incidence of endometriosis). "These factors also apply to the mitochondrial DNA, which is inherited solely from the dam in both male and female offspring (whereas daughters will inherit their sire's X-chromosome). There is evidence that production traits (i.e. weight, marbling) in cattle are affected by variation in mtDNA sequence, which is expected given the role of the mitochondria in energy metabolism. "Monitoring of dam lines via pedigree evaluation and genetic testing is valuable to breeders, therefore. SNP chip testing incorporates both X-chromosome and mtDNA markers which can be employed for this purpose."
Matrilines, by Dr Matt Hegarty content media
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ian
Dec 04, 2021
In Pedigree Q&A
Dam lines are frequently used to name females, e.g. Olde House Caroline 8th. However, it seems to me that unless such founding dams have frequently been bred to sires of similar breeding, then the genetic significance, at least the nuclear DNA of the founding dam in the line, is progressively reduced with each generation. However I understand that the mitochondrial DNA within the unfertilised cell, which has important function, no doubt amongst other things, in respiration (powerhouse of the cell), is inherited from the dam (I see this absolute position disputed), although this varies in species but apparently female ancestry in cattle can be studied through the relatively unchanged passing down of mtDNA from mother to her offspring. One would like to know whether the eggs formed in the female, early on in her life, indeed during embryonic developement, are contributed to by her sire only with respect to half of the half set of nuclear DNA in the unfertilised ovum, or if her sire also contributes to other ovum features, like the cell wall, the cytoplasm, etc. The question boils down to, what do geneticists like Dr. Matthew Hegarty, who provides services to HHBI, or anyone that views this blog, have to say about the importance of dam lines in one's breeding programme in the genetic context?
Dam lines content media
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