Download (1) Division and differentiation in human cells

(1) DIVISION AND
DIFFERENTIATION IN HUMAN CELLS
(F) Cancer
Cells
(A)
Somatic
cells
(B)
Differentiation
in cells
Human
Cells
(C) Stem
cells
(E) Uses
of stem
cells
(D)
Germline
cells
DIVISION AND DIFFERENTIATION
IN HUMAN CELLS (B)
 Define
what is meant by ‘cell
differentiation’
 Define what is meant by ‘selective
gene expression’
 Describe the difference in gene
expression between an
undifferentiated and differentiated
cell.

You have learnt that there are different types
of cells in your body:
 BUT…
we all started off from ONE
fertilised egg!
 How did the variations in cells arise?
 What is this process called?
It’s all to do with your
DNA and a process
called cell
differentiation



Every cell contains DNA (genes)
DNA (genes) carries the code to make a variety of
different proteins
e.g. Hair, nails, antibodies, hormones
CELL DIFFERENTIATION
 Differentiation
is the process by which
an unspecialised cell becomes altered and
adapted to perform a specialised function
as part of a permanent tissue.
 Once
a cell becomes differentiated it
only expresses the genes that code for
the proteins characteristic for that type
of cell.
Fertilised egg cell
Repeated
mitosis and
cell division
Early embryo
(blastocyst)
• Now let’s look at ONE of
these cells...
• Inside the nucleus of ONE
cell, there are ALL the
genes…
• But this cell is destined to
become a blood cell, so it
only switches on the genes,
it NEEDS to the job of a
blood cell
• And switches off the genes
that are not necessary.
Genes switched
on in ALL cells
Genes switched
on in SOME cells
•enzymes needed for
aerobic respiration
•insulin made by
pancreas cells
•proteins in plasma
membrane
•antibody production
Genes that are only
Genes that code for vital
switched on in certain
metabolites necessary
differentiated cells.
for basic life processes
e.g.
e.g.
•Proteins needed to
make cell organelles
•Production of digestive
enzymes
•Production of keratin
SELECTIVE
GENE
EXPRESSION
SELECTIVE GENE EXPRESSION
 Every
cell contains DNA.
 Short sections of DNA which have a specific
job are called genes.
 Genes carry the code to make a variety of
different proteins.
 Not all proteins are needed at the same time.
 Therefore, the genes that control the
production of proteins can be switched on or
off.
 This prevents resources (energy) being
wasted.
SELECTIVE
GENE
EXPRESSION
BACK TO DIFFERENTIATION…
Fertilised egg cell
Early embryo
(blastocyst)
Repeated
mitosis and
cell division
(see figure 1.1 on page 2 for more details!)
Fully grown
adult
Growth and
DIFFERENTIATION
BACK TO
DIFFERENTIATION
&
SELECTIVE
GENE
EXPRESSION
(see figure 1.4
on page 4)