Mammalian chimaeras / Anne McLaren.

  • McLaren, Anne.
Date:
[1976]
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Mammalian chimaeras / Anne McLaren. Source: Wellcome Collection.

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    8 What is a chimaera ? Genes Cell phenotype Organism phenotype Î t Í t Í Î Í ENVI R ONMENT / / Nuclear transfer Cell hybridization / Embryo Chimaeras transfer Fig. 4. Possible levels of interaction between genotype and environment. For explanation see text. 1972; Garcia-Bellido, Ripoll «fe Morata, 1973). The problems that this line of work faces are much greater in mammals than in insects, for a variety of reasons. In mammals cells move around and mingle during development, they interact with one another, and few adequate cell-localized markers are known. The problem of markers will be discussed more fully in Chapter 2. In Drosophila, on the other hand, very little cell mingling occurs, so that a clone usually remains as a coherent group of cells; most characters are cell-autonomous, in that there is rather little intercellular interaction; and the ubiquitous bristles form admirable cell markers, since each bristle is formed by a single cell, many genes are known that affect the structure and colour of bristles, and they are easy to classify. On the other hand, the interactions between cells that make mammalian material less than ideal for the tracing of cell lineages are of particular interest when we come to consider how different cell populations collaborate. The old 'nature-nurture' problem (see Fig. 4) was concerned with how an organism of a particular genetic make-up interacts with its environment to achieve its final adult phenotype, and how much of this phenotype is determined by the genotype and how much by the environment. In mam¬ mals, the environment includes not only the external conditions to which the individual is subjected after birth, but also the maternal environment that it experiences before birth. The technique of embryo transfer can be used to investigate the importance of the maternal environment. When we consider the development of individual cells, we are faced with a more sophisticated extension of the nature-nurture problem, since the en¬ vironment in which a cell develops is made up of the population of other cells surrounding it. In a normal animal each cell is of course surrounded by others