Download Basics of Biology (part 3): transcripCon, translaCon ADN, ARNs

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First step: Transcription !
from DNA to RNA!
RNA (ribonucleid acid) is a single-stranded
polymer, up to few 1000 nucleotides long.!
Its bases differ slightly from DNA: U replaces T!
!
RNA polymerase is an enzyme!
(protein) that unzips DNA and makes
a partial copy into a RNA strand!
It is a molecular motor, it uses ATP to
move along DNA. !
Different types of RNA :!
-  Messenger RNA (mRNA): the one carrying the protein code!
-  Transfer RNA (tRNA): the carrier of amino acids !
-  Ribosomal RNA (rRNA): components of the ribosome!
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2nd step: Translation!
the genetic code!
slation:
three Nucleotides
encode
ananamino
acid
Translation:
three Nucleotides
encode
amino acid
Translation: three Nucleotides encode an amino acid
of three nucleotides
on
es ofSequences
three nucleotides
on
mRNA form
athree
“word”
or “codon”
Sequences
of
nucleotides
on
rm a “word” or “codon”
mRNA form a “word” or “codon”
UAC
UAA
UAC
Tyr
UAA
AUG UAA
Stop
Tyr
Start
Stop
(Met)
Stop
ê
Reminder:!
mRNA, however, does not recognize
1)
in RNA, U replaces T!
amino
acids, thedoes
building
of
mRNA,
however,
not blocks
recognize
2) mRNA
is the one carrying
the
proteins
amino
acids,
the building blocks of
protein
code!
owever,
does not recognize
proteins
3) Reading
goes to
inmRNA
a specific
tRNA binds
and
ds, direction
the building
blocks
of
(UAC≠CAU)
labeled 5’
amino
acidsto mRNA
tRNA
binds
and
to 3’!
amino acid
amino acid
amino acid
Full names of a few amino acids: Ala: Alanine (A)
Gly: Glycine (G)
Arg: Arginine (R) Lys: Lysine (K) 2nd step: Translation!
Transfert RNA!
!
tRNA (transfert RNA) makes the
connection between the code
and the amino acid!
-> it binds to a specific amino acid!
-> it contains the anticodon that
binds to the corresponding
codon on mRNA!
Phenylalanine Symbolic
representation!
of aa-tRNA!
GAA -­‐> an4codon CUU -­‐> codon UUC in the right order (5’ to 3’) cognize
cks of
nd
An4codon onbinds bindsto A
mRNA 2nd step: Translation!
Structure of tRNA!
amino acid
2nd step: Translation - Ribosome!
Protein synthesis is performed in ribosomes
The three-dimensional structure of the
ribosome was solved in atomic detail in 2000
Ribosome: complex of proteins and
ribosomal RNA
Animated protein translation!
Case of a membrane protein translated on the
endoplasmic reticulum!
Source: Wikipedia
Ribosomes are also translating at Institut d’Optique:!
single ribosome observed by fluorescence microscopy!
!
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