B2.3 - cell specialisation (3e) Flashcards
what is the process for the development of an early-stage embryo?
- gametes undergo fertilisation to produce a zygote
- zygote divides by mitosis to form a ball of unspecialised cells
- diffentiation is necessary for embryonic development and leads to the formation of specialised cells
how can there be many different cell types in a body?
some genes, but not others are expressed in each cell type
which method provides biochemical evidence that cells have begun to differentiate?
analysis of proteins:
- different specialised cells will have different concentrations of each protein (proteomes), compared with another type of specialised cell
what is differentiation?
differentiation is a process in which different genes are expressed in a cell
- (ie) a different sub-set of the genes from an organism’s genome
- (ie) a different concentration of protein is produced from a given gene
what is the role of morphogens in control of differentiation?
in early embryos, which genes are expressed in a given cell is controlled by the combination of concentrations of signalling molecules called morphogens
what is the process by which morphogens control differentiation?
- mRNA molecules from “maternal effect genes” are depositied at the poles of the oocyte during oogenesis
- (eg) bicoid mRNA is deposited at what will become the anterior end of the Drosphilia larvae, whilst nanos mRNA is deposited at the posterior end - the gradients of maternal effect proteins are created after fertilisation and multiple rounds of nuclear division. The deposited mRNA is translated and the protein products diffuse away from the site of production
- (eg) bicoid protein is produced in the anterior region of the embryo and diffuses away from this end, whilst nanos protein is produced in the posterior end of the embryo and diffuses away
- the particular combination of concentrations identifies the position of cells in an embryo
- (eg) The higher the concentration of bicoid protein and the lower the concentration of nanos, the closer to the anterior end of the embryo
what are the properties of stem cells?
- stem cells have the capacity to divide endlessly
- stems cells have the capacity to differentiate along different pathways to produce specialised cells
- stem cells are less differentiated than other body cells
what are stem cell niches?
a stem cell niche can maintain the cells or promote their proliferation and differentiation
- thus stem cells are found in large numbers in this region, and tissues form from the differentiated cells are also present
what are 2 examples of stem cell niches?
bone marrow:
- contains stem cells that self-renew to produce blood
- transported in the circulatory system
hair follicles:
contain 2 regions of stem cells:
- bulge stem cells - produce skin, hair and sebaceous gland cells
- dermal papillae - regulates hair follicle development and growth
what are totipotent stem cells?
what are some examples?
embryonic stem cells that can differentiate into all cell types and can form a functional organism
- zygotes and early embryonic stem cells
what are pluripotent stem cells?
what are some examples?
embryonic stem cells that can differentiate into almost all cell types but cannot form a functional organism
- e.g) later embryonic stem cells
what are multipotent stem cells?
what are some examples?
have the ability to differentiate into some cell types
- adult stem cells (bone marrow and hair follicles) and umbilical cord stem cells
what is the maximum amount of identical clones that can be produced by embryo splitting?
16
- this is because after the embryo divides further, the cells are not totipotent, but are pluripotent, so are no longer able to form a new organism
- however, this assumes that only 16 cells are needed to form an organism, which is unlikely
