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One Zygote Divides Into Many Identical Cells That Then Specialise
- At fertilisation a sperm cell fuses with an egg cell to form a single zygote that carries the full genome of the new organism.
- The zygote divides many times by mitosis, producing many genetically identical unspecialised cells.
- These early cells can still give rise to many different cell types, then progressively commit as development continues.
- Each unspecialised cell then differentiates into a specialised cell suited to a particular job.
Analogy
- Every cell holds the same library of songs, which is the genome.
- Each cell type plays a different playlist by expressing a different subset of those genes.
Differentiation: Same Genome, Different Genes Switched On
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- B2.3.1 Production of unspecialized cells following fertilization and their development
- B2.3.2 Properties of stem cells
- B2.3.3 Location and function of stem cell niches in adult humans
- B2.3.4 Differences between totipotent, pluripotent and multipotent stem cells