UNSW Embryology

Week 1 Zygote

© Dr Mark Hill (2009)

Acknowledgements

Introduction

Cleavage of the Zygote: cleavage of zygote forms 2 blastomeres, cleavage with no cytoplasm synthesis, therefore individual cell volume decreases, initially synchronously, then asynchronously (slow- centre cells, larger fast- peripheral cells, flattened against zona pellucida). Note that a recent study has show that the parental genomes remain segregated and that only following the first rounds of cell division does mixing occur. (More? see parental genomes)

Parental Genomes

Up to the 4 cell stage in the preimplantation mouse embryo, the distribution of the 2 parental genomes (chromosomes) remain segregated. After this stage, there is a gradual mixing of the 2 genomes with each cell division.

Distribution of male (green) and female (blue) parental chromosomes (genomes) in the embryo (mouse). Each frame shows progressively later stage in development.

		See movie of images Images- Dr Thomas Haaf

References

• Mayer W, et al. Spatial separation of parental genomes in preimplantation mouse embryos. J Cell Biol. 2000 Feb 21;148(4):629-34.
• Haaf T The battle of the sexes after fertilization: behaviour of paternal and maternal chromosomes in the early mammalian embryo (Review) Chromosome Research 9: 263-271, 2001

Thanks to Dr Thomas Haaf allowing use of his research images on parental genome organization in the preimplantation embryo. (Email: haaf@humgen.klinik.uni-mainz.de)

Quick Links

Week 1 Pages:

Introduction | Abnormalities | Gamete formation | Cell division | Fertilization | Zygote | Blastocyst | Male sex determination| X inactivation | References | Text only page | WWW Links |

Development Notes ----------------- Menstrual Cycle Week 1 Week 2 Week 3 Week 4 Placenta Serial Images Genes/DNA Molecular Dev Abnormal Dev Postnatal Dev Notes Index

System Notes ----------------- Heart/Cardiovascular Respiratory Coelomic cavity Gastrointestinal Tract Head and Neck Neural Neural Crest Eye Ear Nose Endocrine Urogenital Musculoskeletal Integumentary

Movies ----------------- Embryo Growth Ultrasound Week 1 Week 2 Week 3 Week 4 Stage 13/14 Stage 22 Neural Head and Neck Heart Vasculature Gastrointestinal Urogenital Other Embryos Larsen Internet

Other Embryos ----------------- Chicken Fly Frog Mouse Rabbit Rat Worm Zebrafish Guinea Pig

UNSW Embryology ISBN: 978 0 7334 2609 4

UNSW CRICOS Provider Code No. 00098G