How can cells have the same DNA but different proteins?
Different enhancers have different DNA sequences, much like different
bar codes. Each activator recognizes one of the specific enhancer
sequences and “turns on” transcription of the gene associated with it.
The proteins made by a cell depend upon the cell’s combination of
activators. Note that the DNA sequences below are the same, but
each cell has a different combination of activators.
Use the table at right to
determine which mRNA
and proteins are made in
each cell.
Cell #1 is
completed for you.
Enhancer
DNA code
Coding
sequence
Enhancer
Promoter
Activators
in cell
Activator
Terminator
CELL #1
gene C
mRNA
Which proteins
made in cell?
Protein C
Coding
sequence
gene A
Coding
sequence
gene B
Coding
sequence
gene C
CELL #2
Activators
in cell
Coding
sequence
gene A
Coding
sequence
gene B
Which proteins
made in cell?
Coding
sequence
gene C
CELL #3
Activators
in cell
Coding
sequence
gene A
Coding
sequence
gene B
Which proteins
made in cell?
Coding
sequence
gene C
Coding
sequence
gene D
Coding
sequence
gene D
CELL #4
Coding
sequence
gene E
CELL #5
Coding
sequence
gene E
CELL #6
Coding
sequence
gene E
Coding
sequence
gene F
Coding
sequence
gene F
Coding
sequence
gene F
Coding
sequence for
protein
Coding
sequence for
protein
Coding
sequence for
protein
Which proteins
made in cell?
Which proteins
made in cell?
Which proteins
made in cell?
The cells below all have the same DNA sequence. Genes may have more than one enhancer sequence. For example, two
different activators can “turn on” transcription of gene F.
Activators
in cell
Activators
in cell
Activators
in cell
Coding
sequence
gene D