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一、脱氧核糖核酸
cDNA:
互补
DNA
(
Complem
entary DNA
,
cDNA
)<
/p>
是一种利用逆转录酶,
以
RNA
(通常是
mRNA
)
为
模板作成的复制品,经常用来将真核生物的基因(以
mRNA
形
式)复制到原核生物细胞
中。若一个
cDNA
< br>含有许多来自不同基因的
mRNA
,称为
cDNA
基因库(
cDNA library
)
。另外
也可制成只含单一
mRNA
的
cDNA
。
(from wiki)
< br>cpDNA:
叶绿体基因组也叫叶绿体
DNA
(
cpDNA)
,双链环状,每个叶绿体中约含<
/p>
12
个
cpDNA
分子。
叶绿体具有独立基因组,
被认为是内共生起源的细胞器
。
叶绿体基因组主要用于编码
与光合作用密切相关的一些蛋白和
一些核糖体蛋白。
叶绿体基因表达调控是在不同水平上进
行的,
光和细胞分裂素对叶绿体基因的表达也起着重要的调节作用。
gDNA: Genomic DNA.
是区别与染色体之外的
DNA
,如质粒
DNA
等。
gDNA
可以遗传给后代。
msDNA
:
Multicopy
single-stranded DNA (msDNA)
is a type
of
extrachromosomal satellite DNA
that
consists of a single-stranded DNA molecule
covalently linked via a 2'-5'phosphodiester bond
to
an
internal
guanosine
of
an
RNA
molecule.
The
resultant
DNA/RNA
chimera
possesses
two
stem-loops
joined
by a
branch similar to the branches found
in RNA
splicing
intermediates. The
coding region for
msDNA, called a
essential for msDNA
synthesis.[2]
mtDNA
:
Mitochondri
al
DNA
(mtDNA
or
mDNA[2])
is
the
DNA
located
in
organelles
called
mitochondria, structures within
eukaryotic cells that convert the chemical energy
from food into
a form that cells can
use, adenosine triphosphate (ATP). Most
other DNA
present
in eukaryotic
organisms is
found in the cell
是母系遗传的。
rDNA:
Ribosomal
DNA
(rDNA)
codes
for
ribosomal
RNA.
The
ribosome
is
an
intracellular
macromolecule
that
produces
proteins
or
polypeptide
chains.
The
ribosome
itself
consists
of
a
composite of
proteins and RNA. As shown in the
figure, rDNA consists of a tandem
repeat of a
unit segment, an operon,
composed
of NTS, ETS, 18S, ITS1, 5.8S,
ITS2, and 28S tracts. rDNA has
another
gene, coding for 5S rRNA, located in the genome in
most eukaryotes.[1] 5S rDNA is also
present
in
tandem
repeats
as
in
Drosophila.[1]
In
the
nucleus,
the
rDNA
region
of
the
chromosome is visualized
as a nucleolus which forms expanded chromosomal
loops with rDNA.
These rDNA regions are
also called nucleolus organizer regions, as they
give rise to the nucleolus.
In the
human genome there are 5 chromosomes with
nucleolus organizer regions: chromosomes
13,14,15,21 and 22.
染色体上编码
rRNA
的基因。
二、核糖核酸:
mRNA
(前
-mRNA/
不均一核
RNA
)
Messenger RNA (mRNA) is
a molecule of RNA that encodes a
chemical
for
a
protein
product.
mRNA
is
transcribed
from
a
DNA
template,
and
carries coding
information to the sites of protein synthesis: the
ribosomes. Here, the nucleic acid
polymer
is
translated
into
a
polymer
of
amino
acids:
a
protein.
In
mRNA,
as
in
DNA,
genetic
information
is encoded in
the sequence
of nucleotides arranged
into codons consisting of three
bases
each.
Each
codon
encodes
for
a
specific
amino
acid,
except
the
stop
codons,
which
terminate protein
synthesis. This process requires two other types
of RNA: Transfer RNA (tRNA),
that
mediates
recognition
of
the
codon
and
provides
the
corresponding
amino
acid,
and
ribosomal
RNA
(rRNA),
that
is
the
central
component
of
the
ribosome's
protein
-manufacturing
machinery.
tRNATransfer
RNA
(tRNA)
is
an
adaptor
molecule
composed
of
RNA,
typically
73 to 93
nucleotides in length, that is used in biology to
bridge the
four-letter genetic code
(ACGU) in messenger RNA (mRNA) with the
twenty-letter
code
of
amino
acids
in
proteins.[1]
The
role
of
tRNA
as
an
adaptor is best understood by
considering its three-dimensional
structure.
rRNA
:
Ribosomal
ribonucleic acid (rRNA) is the RNA component of
the
ribosome,
the
enzyme
that
is
the
site
of
protein
synthesis
in
all
living
cells. Ribosomal RNA provides a
mechanism for decoding mRNA into amino
acids and interacts with tRNAs during
translation by providing
peptidyltransferase
activity.
The
tRNAs
bring
the
necessary
amino
acids
corresponding to the
appropriate mRNA codon.
Inside the
ribosome
The ribosomal RNAs
form two subunits, the large subunit (LSU) and
small
subunit (SSU). mRNA is sandwiched
between the small and large subunits
and the ribosome catalyzes the
formation of a peptide bond between the
2 amino acids that are contained in the
rRNA.
A ribosome also has 3 binding
sites called A, P, and E.
The A site in
the ribosome binds to an aminoacyl-tRNA (a tRNA
bound to
an amino acid).
The
amino
(NH2)
group
of
the
aminoacyl-
tRNA,
which
contains
the
new
amino
acid, attacks the ester linkage of
peptidyl-tRNA (contained within the
P
site),
which
contains
the
last
amino
acid
of
the
growing
chain,
forming
a
new peptide bond. This reaction is catalyzed by
peptidyltransferase.
The tRNA that was
holding on the last amino acid is moved to the E
site,
and what used to be the
aminoacyl-tRNA is the peptidyl-tRNA.
A
single mRNA can be translated simultaneously by
multiple ribosomes.
Prokaryotes vs.
Eukaryotes
Both prokaryotic and
eukaryotic ribosomes can be broken down into two
subunits (the S in 16S represents
Svedberg units
沉降单位
):
Note
that
the
S
units
of
the
subunits
cannot
simply
be
added
because
they
represent measures of
sedimentation rate rather than of mass. The
sedimentation rate of each subunit is
affected by its shape, as well as
by
its mass.
Prokaryotes
In prokaryotes a small 30S ribosomal
subunit contains the 16S rRNA.
The
large
50S
ribosomal
subunit
contains
two
rRNA
species
(the
5S
and
23S
rRNAs).
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