Sheep's wool: Difference between revisions
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Sheep (<i>Ovis aries</i>) have been selectively bred to continuously produce single coated wool fleece rather than coats composed of an outer hair layer and an inner wool layer.<ref>Ryder M. A survey of European primitive breeds of sheep. <i>Ann Genet Sel Anim.</i> 1981;13(4):381-418. doi:10.1186/1297-9686-13-4-38</ref> True wool, as opposed to hair, is characterised by its high follicle density in the skin, small diameter, and high crimp (waviness) <ref name="doyle">Doyle EK, Preston JWV, McGregor BA, Hynd PI. The science behind the wool industry. The importance and value of wool production from sheep. Anim Front. 2021;11(2):15-23. Published 2021 May 17. doi:10.1093/af/vfab005</ref> | Sheep (<i>Ovis aries</i>) have been selectively bred to continuously produce single coated wool fleece rather than coats composed of an outer hair layer and an inner wool layer.<ref>Ryder M. A survey of European primitive breeds of sheep. <i>Ann Genet Sel Anim.</i> 1981;13(4):381-418. doi:10.1186/1297-9686-13-4-38</ref> True wool, as opposed to hair, is characterised by its high follicle density in the skin, small diameter, and high crimp (waviness) <ref name="doyle">Doyle EK, Preston JWV, McGregor BA, Hynd PI. The science behind the wool industry. The importance and value of wool production from sheep. Anim Front. 2021;11(2):15-23. Published 2021 May 17. doi:10.1093/af/vfab005</ref> | ||
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The single woolly coat is recessive trait caused by the insertion of an antisense EIF2S2 retrogene<ref>Staszak K, Makałowska I. Cancer, Retrogenes, and Evolution. <i>Life (Basel).</i> 2021;11(1):72. Published 2021 Jan 19. doi:10.3390/life11010072</ref> into the 3′ untranslated region of the IRF2BP2 gene.<ref name="demars">Demars J, Cano M, Drouilhet L, et al. Genome-Wide Identification of the Mutation Underlying Fleece Variation and Discriminating Ancestral Hairy Species from Modern Woolly Sheep. <i>Mol Biol Evol.</i> 2017;34(7):1722-1729. doi:10.1093/molbev/msx114</ref> This gene mutation creates a chimeric IRF2BP2/asEIF2S2 RNA transcript that targets the genuine sense EIF2S2 mRNA and creates EIF2S2 dsRNA that regulates the production of EIF2S2 protein <ref name="demars"></ref>. | The single woolly coat is recessive trait caused by the insertion of an antisense EIF2S2 retrogene<ref>Staszak K, Makałowska I. Cancer, Retrogenes, and Evolution. <i>Life (Basel).</i> 2021;11(1):72. Published 2021 Jan 19. doi:10.3390/life11010072</ref> into the 3′ untranslated region of the IRF2BP2 gene.<ref name="demars">Demars J, Cano M, Drouilhet L, et al. Genome-Wide Identification of the Mutation Underlying Fleece Variation and Discriminating Ancestral Hairy Species from Modern Woolly Sheep. <i>Mol Biol Evol.</i> 2017;34(7):1722-1729. doi:10.1093/molbev/msx114</ref> This gene mutation creates a chimeric IRF2BP2/asEIF2S2 RNA transcript that targets the genuine sense EIF2S2 mRNA and creates EIF2S2 dsRNA that regulates the production of EIF2S2 protein <ref name="demars"></ref>. | ||
[[Image:PHIL_1181_lores.jpg|thumb|300px|left|Figure 1. Electron micrograph of the Ebola Zaire virus. This was the first photo ever taken of the virus, on 10/13/1976. By Dr. F.A. Murphy, now at U.C. Davis, then at the CDC.[https://phil.cdc.gov/details.aspx?pid=1833].]] | |||
[[File:Merino sheep.png|Merino_sheep]] | |||
==Wool structure== | ==Wool structure== | ||
Revision as of 00:17, 11 December 2024
Introduction
Sheep (Ovis aries) have been selectively bred to continuously produce single coated wool fleece rather than coats composed of an outer hair layer and an inner wool layer.[1] True wool, as opposed to hair, is characterised by its high follicle density in the skin, small diameter, and high crimp (waviness) [2]
The single woolly coat is recessive trait caused by the insertion of an antisense EIF2S2 retrogene[3] into the 3′ untranslated region of the IRF2BP2 gene.[4] This gene mutation creates a chimeric IRF2BP2/asEIF2S2 RNA transcript that targets the genuine sense EIF2S2 mRNA and creates EIF2S2 dsRNA that regulates the production of EIF2S2 protein [4].
Wool structure
All hair and wool fibers are composed of an cuticle layer of overlapping cells wrapped around a cortex. Coarse wools and many animal fibers also contain a medulla consisting of empty vacuoles.
Wool has a cuticle layer that is only one cell thick, while human hair, for example, has a cuticle layer up to 10 cells thick. Wool cuticle cells also have a wedge-shaped shaped cross-section as opposed to rectangular, so the exposed edge height of wool cuticle cells is about 1 um as opposed to < 0.5 um in other animal fibers.[5]
Wool’s crimp is generally attributed to its cortex structure.[5][6] Highly crimped fibers have a well defined bilateral segmentation of para-cortical and ortho-cortical cells, with the ortho-cortex on the outside of the wave. Less crimped fibers have meso-cortical cells replace some of the para-cortical cells.
Microbial interactions with wool
References
- ↑ Ryder M. A survey of European primitive breeds of sheep. Ann Genet Sel Anim. 1981;13(4):381-418. doi:10.1186/1297-9686-13-4-38
- ↑ Doyle EK, Preston JWV, McGregor BA, Hynd PI. The science behind the wool industry. The importance and value of wool production from sheep. Anim Front. 2021;11(2):15-23. Published 2021 May 17. doi:10.1093/af/vfab005
- ↑ Staszak K, Makałowska I. Cancer, Retrogenes, and Evolution. Life (Basel). 2021;11(1):72. Published 2021 Jan 19. doi:10.3390/life11010072
- ↑ 4.0 4.1 Demars J, Cano M, Drouilhet L, et al. Genome-Wide Identification of the Mutation Underlying Fleece Variation and Discriminating Ancestral Hairy Species from Modern Woolly Sheep. Mol Biol Evol. 2017;34(7):1722-1729. doi:10.1093/molbev/msx114
- ↑ 5.0 5.1 Wortmann, F.-J. (2009). The structure and properties of wool and hair fibres. Handbook of Textile Fibre Structure, 108–145. doi:10.1533/9781845697310.1.1
- ↑ Marshall RC, Orwin DF, Gillespie JM. Structure and biochemistry of mammalian hard keratin. Electron Microsc Rev. 1991;4(1):47-83. doi:10.1016/0892-0354(91)90016-6
Edited by Isaac Yu, student of Joan Slonczewski for BIOL 116, 2024, Kenyon College.
