TwoOldGuys Study Guides
BI-122 Biology
mRNA & DNA
mRNA
- the rRNA could determine which AA is which by its tRNA "tag,"
- but the ribosome needs to know which AA it ought to be looking for.
- The simplest way to provide this message:
- convert the AA sequence of the desired protein to a list of tRNA codes
- deliver this list as a single large molecule of RNA, called messenger RNA [or mRNA].
- Due to nucleotide pairing 'rules' the mRNA must list the opposite of what it means.
- the tRNA, AGC which codes for Ser,
would be listed on the mRNA as UCG.
- given the 'protein' from before:
- and the attached tRNA molecules:
- Met-UAC
- Gly-CCA, Gly-CCG, Gly-CCU, or Gly-CCC
- Ser-AGA, Ser-AGG, Ser-AGU, Ser-AGC, Ser-UCA, or UCG
- Glu-CUU, or Glu-CUC
- Val-CAA, Val-CAG, Val-CAU, or Val-CAC
- STOP = AUU, AUC, or ACU
- one possible mRNA to describe the tRNA sequence, therefore AA sequence:
- AUG,GGC,UCG,GAG,GUC,UAA
- or without the commas
- AUGGGCUCGGAGGUCUAA
Total # mRNA for
Met-Gly-Ser-Glu-Val-STOP
# tRNA's |
AA= |
Met |
Gly |
Ser |
Glu |
Val |
STOP |
|
1 |
4 |
6 |
2 |
4 |
3 |
1 |
4 |
6 |
2 |
12 |
1 |
4 |
6 |
24 |
1 |
4 |
144 |
1 |
576 |
576 |
DNA
- Complete set of instructions for all protein synthesis required by an organism
- stored in Nucleus as even larger molecules, listing all required mRNA molecules
- substituting deoxyribose, we have DNA
- applying nucleotide pairing rules, again we produce the opposite:
recall DNA substitutes Thymidine [T] for Uracil [U]
tRNA |
mRNA |
DNA |
DNA |
code |
complement |
A |
U |
A |
T |
G |
C |
G |
C |
U |
A |
T |
A |
C |
G |
C |
G |
- given the mRNA from earlier:
- the coding DNA would be:
Genetics:
DNA to Protein
transcription |
DNA |
TAC |
CCG |
AGC |
CTC |
CAG |
ATT |
mRNA |
AUG |
GGC |
UCG |
GAG |
GUC |
UAA |
translation |
tRNA |
UAC |
CCG |
AGC |
CUC |
CAG |
AUU |
protein |
fMet |
Gly |
Ser |
Glu |
Val |
STOP |
- copying of information from DNA to mRNA is
transcription
- using information from mRNA for Protein synthesis is
translation
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© 2004-2005 TwoOldGuys
revised 19 aug 2006