Bio study guide IV Reading 18 4 18 5 21 6 1 Be able to explain how the concentration of cytoplasmic determinants leads to differences in cell determination in early development course of early development a Cytoplasmic determinants are the maternal substances in the egg that influence the i MRNA proteins other substances are distributed unevenly in the unfertilized egg and this unevenness definitely has an impact on the development of the future embryo b Another thing that affects development is the environment around a cell becoming really important as the number of embryonic cells increases c Cell determination gives a cell its fate for when it develops later on i So they lead to differences in cell determination in early development because every cell is going to be different for when its fate is determined d Cell differentiation is the process by which cells become specialized in structure and function i Induction is when signals from nearby embryonic cells cause changes in the target cells these signals affect development because they send a cell down a certain developmental path by causing changes in its gene expression that eventually result in observable cellular changes 1 Thus these interactions btwn embryonic cells help induce differentiation of the many specialized cell types making up a new organism e DETERMINATION COMES BEFORE DIFFERENTIATION ONCE A CELL UNDERGOES DIFFERENTIATION IT IS PERMANENTLY ON THAT PATH TO BECOME THAT CERTAIN CELL TYPE 2 Know that genes controlling development are expressed in a specific sequence a The outcome of determination observable cell differentiation is marked by the expression of genes for tissue specific proteins i These proteins are only found in a specific cell type and give the cell its characteristic structure and function ii On the molecular level different sets of genes are sequentially expressed in a regulated manner as new cells arise from division of their precursors 1 Several steps in gene expression can be regulated especially transcription remaining as the principal regulatory point for maintaining appropriate gene expression 2 The master regulatory gene in muscle cells is a major factor that contributes to the process of transcription to express MyoD and therefore create skeletal muscle cells 3 Know that the earliest genes expressed determine axis polarity followed by organization into body regions segmentation and specific characteristics Drosophila a Pattern formation a spatial organization in which the tissues and organs of an organism are all in their characteristic places cytoplasmic determinants and inductive signals both contribute to this b Certain molecular cues that control pattern formation called positional information are provided by cytoplasmic determinants and inductive signals these cues tell a cell its location relative to the body axes and to neighboring cells and determine how the cell and its offspring will respond to future molecular signals 4 Know that developmental genes are highly conserved across animals be able to explain what highly conserved means a Researchers discovered very similar nucleotide sequences aka homeobox btwn drosophila flies and other organisms especially humans b Hox genes are highly conserved across animals humans have the same genes as fruit i The order on the body in which Hox genes are expressed is the same as the flies order on the chromosome c Highly conserved
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