Detection of quantitative trait loci for growth and beef carcass quality traits in a cross of Bos taurus x Bos indicus cattle /
Quantitative trait loci (QTL) affecting growth and beef carcass quality traits were studied in a three generation mapping population with 614 progeny from 26 reciprocal fullsib backcross and two F[] families of 80 Brahman, Angus and F[] parents and grandparents. Four hundred seventeen genetic marker...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=731685711&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Quantitative trait loci (QTL) affecting growth and beef carcass quality traits were studied in a three generation mapping population with 614 progeny from 26 reciprocal fullsib backcross and two F[] families of 80 Brahman, Angus and F[] parents and grandparents. Four hundred seventeen genetic markers were scored to produce a sex-average map of the 29 autosomes and X chromosome spanning 2657cM. A line-cross model and an across-breed model were used to detect QTLs segregating between Angus and Brahman, within each breed or across both breeds, respectively. Three QTLs with significant, 17 QTLs with suggestive and 13 QTLs with chromosome-wise evidence for linkage were detected on eighteen out of 29 bovine chromosomes. Nine QTLs were detected with at least suggestive evidence under the across-breed model, supporting the existence of allelism across breeds with quite different growth and carcass characteristics. Ten QTLs with a dominant mode of gene action were detected with at least chromosome-wise evidence under the line-cross model. The use of both models provided complementarity in examining the underlying assumptions about allelic effects and frequencies in an sutured line-cross. The halfsib analysis provided insight into frequency skewness of line-specific alleles. Most detected QTLs for birth weight (BWT) were additive in their action, while those for weaning weight (WWT) and hot carcass weight (HCWT) were dominant, suggesting different natures of gene action for the QTLs expressed at different stages of growth. There was no strong evidence of an additive relationship between adjusted back fat (ADF) and kidney, pelvic and heart fat (KPH), suggesting that different genes influence external and internal fatness. Confidence interval (CI) size from selective bootstrapping (Selective II) with 90% confidence limit was as small as and similar to that produced by the one LOD-drop method. However, some CIs derived from Selective II were asymmetrically distributed but others appeared to be too small to achieve the nominal significance level and thus were not useful for defining chromosomal segments harboring QTLs for the application of marker-assisted selection (MAS). |
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| Item Description: | Vita. "Major Subject: Animal Breeding". |
| Physical Description: | xiv, 149 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 103-109). |