LESSON 1: THE
DEVELOPMENT OF CELLS
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Multicellular organisms are composed of
not only many cells, but many different types of cells. Yet all
of the cells of an organism develop from one, original cell,
spore or a
zygote. How do these cells become
differentiated from one another, so that they may perform
specific roles for an organism?
The way in which these cells become
specialized starts out with some type of signal, usually a
chemical signal. In response to a given signal or signals, cells
can change the way they function and develop, most often by
controlling what genes are expressed at what time. This process
differentiation happens most
commonly in developing embryos, where the cells don’t yet have a
specific function, but can occur in certain cells of adult
Understand the processes of signal
transduction, and how they are important for all cells.
Understand the concepts of cell
determination and differentiation, and how these processes
are effected in developing cells.
Learn how developmental genes are
expressed in a hierarchical manner.
Be familiar with common early
stages of development.
Understand the factors influencing
the development of shape in tissues, organs, and bodies.
Topics covered in this Lesson
you go through the next few lessons, try to paint a picture in
your head of the ways in which cells change and develop in
embryos and organisms. Basically, organisms begin life as a cell
whose only developmental restrictions are based on the genome it
carries. For instance, an early embryonic animal cell does not
have the proper genes to develop into a leaf, but it can develop
into any cell type found in the mature animal. Cells with such
unlimited developmental potential, like cell of very early
embryos, are often referred to as
totipotent. As an organism develops, the processes
of cell signaling, cell determination and cellular
differentiation lead to the maturation of cells and tissues that
perform specific functions for an organism.
- Why do most all individuals in a
species have the same basic body structure?
- Understand the cellular causes of
- Be able to describe the general
process by which expression of genes is controlled
- Understand some of the key
differences and similarities among very different
have developed complex ways of receiving and responding to signals
from other cells and from their environment. In this lesson we will
look at the process of
signal transduction, in which signals are received by
cells and translated into an appropriate cellular response. Cells
receive signals at the cell membrane or within the cytoplasm,
amplify the signals, and finally respond to the signal in one of
several ways. Cell signaling plays a vital role in the development
of organisms, and in the regulation and activity of mature cells and
What is a signal transduction
Know what a ligand is.
Understand the four basic
receptors and how they work to receive and transmit
Understand the general
differences between membrane-bound receptors and
Be able to describe three
common cellular responses to cell signals.
Be able to describe how a
protein kinase cascade works and why it is useful.
Understand what second
messengers are and what they do. Be familiar with
several examples of second messengers.
few exceptions, all of the cells in a multicellular organism contain
the same DNA. This is not surprising, given that organisms develop
from mitotic divisions of one original cell, called a
zygote. However, it is clear that there are many different cell
types in the bodies of multicellular organisms. How do these cells
‘mature’ to take on specific roles for an organism? This module will
explore the processes by which cells mature, commonly referred to as
cell determination and differentiation.
Understand the difference
between determination and differentiation as it pertains
to cell development.
Be able to explain how the
developmental fate of cells becomes less flexible over
time in a developing embryo.
What molecular processes lead
to cell determination and differentiation? In other
words, how can cells with the same genetic information
look and function differently?
stem cells are, know the different types of stem cells, and why
they are so useful/important to medical research.