Uploaded January 2025 | Updated September 2026, 1 day ago

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In this video, we look at homeobox genes and body plans. First we explore what is meant by a homeobox gene and why homeobox genes are transcription factors. We then look at Pax6 and its role in eye development. We explore diploblastic and triploblastic organisms and segmentation. We then look at Hox genes and how they direct the development of somites in the embryo. We explore the roles of mitosis and apoptosis in the development of body plans. Finally, we look at how development can be influenced by external factors including drugs such as thalidomide.

Image credits:

Zygote
commons.wikimedia.org/wiki/File:Zygote1.jpg
Nina Sesina, CC BY-SA 4.0 creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

Human embryo 8 cells
commons.wikimedia.org/wiki/File:Embryo,_8_cells.jpg
ekem, Public domain, via Wikimedia Commons

3 month old foetus
commons.wikimedia.org/wiki/File:4dsonogram.jpg
Madcapslaugh, Public domain, via Wikimedia Commons

Goose
commons.wikimedia.org/wiki/File:Graugans_Anser_Anser.jpg
H005, denoised by Pro2, Public domain, via Wikimedia Commons

Large eyed mini wolf spider
commons.wikimedia.org/wiki/File:Large-eyed_mini_wolf_spider_(Minicosa_neptuna).jpg
RudiSteenkamp, CC BY-SA 4.0 creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

Daffodil
commons.wikimedia.org/wiki/File:Narzisse.jpg
Martin Hirtreiter, CC BY 3.0 creativecommons.org/licenses/by/3.0, via Wikimedia Commons

Hox genes of fruit fly
commons.wikimedia.org/wiki/File:Hoxgenesoffruitfly.svg
PhiLiP, Public domain, via Wikimedia Commons

Fruit fly
commons.wikimedia.org/wiki/File:Drosophila_melanogaster_-_side_(aka).jpg
André Karwath aka Aka, CC BY-SA 2.5 creativecommons.org/licenses/by-sa/2.5, via Wikimedia Commons

Pax6 mutations
commons.wikimedia.org/wiki/File:PAX6_Phenotypes_Washington_etal_PLoSBiol_e1000247.png
Washington NL, Haendel MA, Mungall CJ, Ashburner M, Westerfield M, Lewis SE., CC BY 2.5 creativecommons.org/licenses/by/2.5, via Wikimedia Commons

Antennapedia mutant
commons.wikimedia.org/wiki/File:Mutation_Antennapedia.jpg
toony, CC BY-SA 3.0 creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons

Homeobox genes big picture (modified by S. Donnelly)
commons.wikimedia.org/wiki/File:Genes_hox.jpeg
Stefanie D. Hueber, Georg F. Weiller, Michael A. Djordjevic, Tancred Frickey, CC BY 4.0 creativecommons.org/licenses/by/4.0, via Wikimedia Commons

1NK2-NK2 homeodomain
commons.wikimedia.org/wiki/File:1NK2-NK2_homeodomain_DNA_complex.png
Takuma-sa, CC0, via Wikimedia Commons

Jellyfish
commons.wikimedia.org/wiki/File:Chrysaora_jelly.jpg
This image is in the public domain.

Somites in mouse foetus
commons.wikimedia.org/wiki/File:Scanning_electron_micrograph_of_an_11.5_day_old_mouse_foetus_showing_the_limb_buds,_somites_and_branchial_arches.jpg
Paul Martin, CC0, via Wikimedia Commons

Gastrulation (modified by S. Donnelly)
commons.wikimedia.org/wiki/File:Early_gastrulation_in_amphibian_embryos.png
Kumar, V.; Park, S.; Lee, U.; Kim, J., CC BY 4.0 creativecommons.org/licenses/by/4.0, via Wikimedia Commons

Jellyfish 3
commons.wikimedia.org/wiki/File:Aurelia_aurita_2.jpg
© Hans Hillewaert

Jellyfish 4
commons.wikimedia.org/wiki/File:Aurelia_aurita_(auge24eu).jpg

Andreas Augstein, CC BY 3.0 creativecommons.org/licenses/by/3.0, via Wikimedia Commons

Butterfly
commons.wikimedia.org/wiki/File:Inachis_io_Lill-Jansskogen.JPG
Korall, CC BY-SA 3.0 creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons

Somites in chick
commons.wikimedia.org/wiki/File:Aves_Neural_tube_and_somites_in_chick_embryo.jpg
Prof. R. Bellairs, CC BY 4.0 creativecommons.org/licenses/by/4.0, via Wikimedia Commons

Centipede
commons.wikimedia.org/wiki/File:Chilopoda-_Geophilomorpha_(3310072328).jpg
Mick Talbot from Lincoln (U.K.), England, CC BY 2.0 creativecommons.org/licenses/by/2.0, via Wikimedia Commons

Earthworm
commons.wikimedia.org/wiki/File:Earthworm_02.jpg
Rob Hille, CC BY-SA 3.0 creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons

Snake skeleton
commons.wikimedia.org/wiki/File:Bitis_gabonica_complete_skeleton.jpg
Stefan3345, CC BY-SA 4.0 creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

Mouse embryo hand
commons.wikimedia.org/wiki/File:Handentwicklung_Maus_vier_Phasen.jpg
Ventus55, CC BY-SA 3.0 creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons

Thalidomide
commons.wikimedia.org/wiki/File:Thalidomide_structure.svg
Aethyta, Public domain, via Wikimedia Commons

AI Avatar
commons.wikimedia.org/wiki/File:AI_Avatar.jpg
PedroXBC, CC BY-SA 4.0 creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons