Biology 3338A Lecture Notes - Lecture 7: Spindle Apparatus, Actomyosin Ring, Cytochalasin
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But mammals have unique cleavage patterns ie. not as conserved within species. Fertilized mammal eggs are also small with very little stores as it attaches to uterus to get nutrients from mother. Fertilized eggs do not grow in mass ie. chicken egg is one cell out of which chick hatches. That chick has same mass as fertilized egg did at the very beginning before cleavage, gastrulation, etc. But mammal fertilized eggs do grow in mass as they get plenty of nutrients from mother. Frog genomic transcription is activated later after several cell divisions. Maternal factors in egg cell control these early mitotic divisions. Egg has everything required for these initial divisions. Different in mammals as start using zygotic dna in 2-cell stage. To speed things up, gap periods do not occur (left) as they do in normal mitosis (right) In normal mitosis, mitosis ie. cell division, then g1 phase, then s phase ie.