Biomedical Engineering Reference
In-Depth Information
across Hydrogen Bonds. Thymine binds to
adenine and guanine to cystosine in DNA,
and uracil binds to adenine in the case of
RNA. The single strands have different
ends called 3' and 5'. This implies that the
hybridization of the two single strands is
antiparallel, i.e. the 3' end of one strand binds
to the 5' end of the other and vice versa.
•
Promoter:
region to which the RNA
polymerase (RNAp) enzyme binds to start
transcription. It is positioned in front of the
gene.
•
Operator:
region to which the regulatory
proteins bind to stimulate or inhibit gene
transcription. It can be positioned in front
of, behind or inside the promoter.
•
DNA double helix:
DNA in living cells
generally has a double helix structure formed
by two interwoven strands that are linked
by complementary bases. The length per
turn is 34 Angstroms and its diameter is 20
Angstroms.
•
Terminator:
region where gene transcrip-
tion ends. It is positioned at the end of the
gene.
•
Regulatory sequence:
region where the pro-
teins regulating gene transcription are coded.
There may be several sequences positioned
at either the start or end of the gene. These
sequences can be far away from the gene and
also in different double helix strands. Note
that the first regulatory sequence in Figure
1 is not in the same strand as the gene.
•
Gene:
A gene is the building block of in-
heritance in living beings. Physically, it is
portion of one of the two strands of DNA
making up the double helix and is composed
of a nucleotide sequence that contains the
information for RNA molecule synthesis.
•
Regulatory proteins:
are proteins that
bind to the gene operator and act differently
depending on whether they are repressors
or activators. Repressor proteins directly
Additionally, a gene has neighbouring portions
with special functions (Figure 1):
Figure 1. Gene of one of the strands of the DNA double helix
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