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RNA
DNA is the genetic material….
•It carries the genetic code
•DNA needs RNA to carry this code out
to the cytoplasm
How is DNA different from RNA?
What else is different between DNA and RNA?
To sum it up:
RNA is made by the process of transcription:
There are many different kinds of RNA:
•mRNA (messenger RNA): carry information
from DNA to the ribosomes to make
proteins
•rRNA (ribosomal RNA): part of ribosomes
•tRNA (transfer RNA): brings amino acids to
the ribosomes
RNA polymerase binds to the promoter on DNA:
Then, RNA polymerase matches complementary
RNA nucleotides to the DNA nucleotides:
Eventually, the RNA polymerase reaches the
termination sequence:
After it is made, the RNA needs to be edited”
The new RNA leaves
the nucleus and
enters the cytoplasm
RNA has the information to make proteins
•We say mRNA codes for proteins
•Where was this information before any
mRNA was made? _____________________
•HOW does RNA code for proteins?
•The triplet code:
How does the mRNA tell us which
amino acid comes next?
•Each 3 bases in mRNA codes for one
amino acid:
One codon is specific for ‘start’:
Several codes are specific for ‘stop’:
Let’s look up the amino acids coded for by the
following mRNA sequences:
1. AUG CCA GAC CCG AAU
________________________________________
2. AUG GAT UUU AUA CGC
________________________________________
3. AUG CAC CUC GUC AGG
________________________________________
TRANSLATION is the process by which cells take
the triplet code and translate it into a string of
amino acids called a polypeptide
• this requires mRNA, tRNA, and a ribosome
•There are THREE steps:
1. Initiation (starting)
2. Elongation (growing the polypeptide)
3. Termination (ending)
What is tRNA? (transfer RNA)
INITIATION:
•An mRNA finds and binds to a ribosome
Elongation:
Termination: