Biomedical Engineering Reference
In-Depth Information
HO
O
P
P
O
O
O
O
O
5
O
3
2
4
1
1
4
2
3
O
(Cytosine)
C
G
(Guanine)
5
HO
O
H
HO
O
H
P
N
P
N
O
O
O
O
N
5
O
N
3
2
N
4
1
4
1
O
3
2
(Adenine)
A
T
(Thymine)
5
HO
O
H
HO
O
H
P
N
P
N
O
O
O
O
N
5
O
N
3
2
N
4
1
4
1
O
3
2
(Thymine)
T
A
(Adenine)
5
O
O
FIGURE 2.32
Molecular structure of DNA. The
b
-strand (left) and the
a
-strand (right) are linked to form double
strands through hydrogen bonds between base units. The hydrogen bonds bring extra stability to the double
strands. The pairing of the bases are (T
e
A), (A
e
T), (C
e
G), and (G
e
C). While bases bonded to the
b
-strand are
mirror images of those bonded to the
a
-strand, the deoxyribose sugar backbones are not mirror images of one
another between the
b
-strand and the
a
-strand.
can encode factors that protect cells from antibiotics or harmful chemicals. Linear rather than
circular plasmids can be found in some yeasts and other organisms.
The major function of DNA is to carry genetic information in its base sequence. The genetic
information in DNA is first transcribed into RNA molecules and then translated in protein
synthesis. The templates for RNA synthesis are DNA molecules, and RNA molecules are
the templates for protein synthesis. The formation of RNA molecules from DNA is known
as DNA transcription, and the formation of peptides and proteins from RNA is called
translation.
Certain RNA molecules function as intermediates carrying genetic information in protein
synthesis (messenger or mRNA), whereas other RNA molecules (transfer tRNA and ribosomal
rRNA) are part of the machinery of protein synthesis. The rRNA is located in ribosomes which
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