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Notes

• Subtopic: Evolution and Development Evolution and development explain how undifferentiated cells become specialized cells, creating different structures with different phenotypes of the body. Evolutionary developmental biology combines developmental biology with evolutionary biology. The main idea of the video on fruit flies is that the differences in body parts of organisms depend on when and where genes are expressed. This expression directs whether a structure is present and its placement on the organism. - **WHEN**: At what time of an animal's development. - **WHERE**: In which part or area of the body. We refer to the Hox genes. The structure consists of segments with appendages and repetition or symmetry. The timing and location of gene expression not only determine if an appendage is formed but also the overall pattern and organization of the body. • Subtopic: Gene Expression in Multicellular Creatures Multicellular creatures develop from a single cell, the zygote. Gene expression involves the transcription of DNA into mRNA. Each somatic cell has the same set of genes. So, why do they become different? The differences arise from variations in gene expression. • Subt...