RNA
STRUCTURE
TYPES OF RNA
TRANSCRIPTION
Learning Targets
Students will be able to compare and contrast DNA and RNA
Students will be able to identify the job of RNA
Structure of RNA
Single-stranded polymer
made of repeating
nucleotides
 RNA = Ribonucleic Acid
 Contains a phosphate
group
 Contains a RIBOSE sugar
(instead of deoxyribose!)
– has an oxygen
 Contains nitrogen
bases…C, A, G and U!

 RNA
has URACIL instead of
thymine!!!!
How
does
RNA
compare
to DNA?
3 Types of RNA
1. Messenger RNA (mRNA) – “records”
information from the DNA in the nucleus and
transports it out of the nucleus to the ribosomes
3 Types of RNA
2. Transfer RNA (tRNA) - deliver
amino acids one by one to
protein chains forming at
ribosomes
3. Ribosomal RNA (rRNA) –
found in the ribosomes;
helps with ribosome’s
structure, although the
function is not completely
understood
Why is RNA important?

Because it is involved
with protein synthesis!

DNA risks being
damaged if it leaves
the nucleus, so mRNA
copies the info from
the DNA to bring it out
to the ribosomes and
tRNA helps to bring the
amino acids to the
ribosome to form the
protein strands
How do we get mRNA from DNA?
A process called TRANSCRIPTION
 4 steps similar to DNA replication, but with a
different end result

What do you notice is
different from DNA
replication?
Only 1 single strand is
produced!
Transcription

Step 1 – DNA gets “unzipped” - helicase

Step 2 – RNA polymerase guides RNA
nucleotides to line up in the proper order by
hydrogen-bonding to their complementary
bases on one side of DNA
Transcription

Step 3 – Covalent bonds form along the
sugars & phosphates to hold the mRNA
together

Step 4 - transcription continues until a “stop
sign” is reached and the mRNA strand is
complete

Transcription Animation
The Genetic Code

Each set of 3 nitrogen bases represents
1 amino acid = CODON

64 possible codons
3
code “stop”
 61 code for amino acids (20 different a.a.)
 1 codes to “start” – AUG = methionine

Code is UNIVERSAL – codons represent
the same amino acids in all organisms
Use your codon chart to answer the following:

1. How many different
codons code for valine?


2. The codon CGU is for
which amino acid?


Arginine
3. What are the codons for
the three “stops”?


4
UAA, UAG, UGA
4. What are the first 3 amino
acids for this strand of mRNA?

Alanine, Threonine, Glutamic acid