1. RiboNucleic Acid Also made of monomers called nucleotides
5 carbon sugar: Ribose
Phosphate functional group: PO4
1 of 4 nitrogen bases
Cytosine
Guanine
Adenine
Uracil replaces Thymine
Molecule is a single strand

2. Purpose of RNA
There are many types of RNA, so function varies depending upon type:
Determines which genes are expressed
Some regulate chemical processes, so, they function like enzymes
Small sections of RNA act as place holders for DNA polymerase during DNA replication
Directly involved in converting genetic code on DNA into proteins

3. 3 TYPES OF RNA USED IN PROTEIN SYNTHESIS
messenger RNA(mRNA)
Long, single strand
Made in the nucleus
Carries genetic code
from DNA to ribosomes
in cytoplasm

4. transfer RNA (tRNA) Folded chain of RNA Carries the amino
acid monomers that
make a protein
“Translates” the
genetic code

5. Ribosomes ribosomal RNA (rRNA) Globular strand of RNA
2 parts: large and small subunits
Located on the ER and
free floating in cytoplasm
Site of protein synthesis

6. Why is mRNA needed in the first place
Why is mRNA needed in the first place? DNA carries the code, however, DNA cannot leave the nucleus. RNA carries the “genetic message” to ribosomes Why change a base? The nuclear envelope “recognizes” the bases on DNA and keeps it in the nucleus; by changing a single base on RNA, its chemical signature changes, so the nuclear envelope will allow it to pass through to cytoplasm Why not just make proteins in the nucleus? Proteins are “huge” molecules. There’s just not enough room in the nucleus to make all the proteins an organism requires, so the protein factory (ribosomes, ER and Golgi Body) is out in the cytoplasm where there’s plenty of space. Why are ribosomes on the ER and in the cytoplasm? Proteins are needed for many functions. The proteins made in ribosomes on the ER are transported either to the nucleus or out of the cell(hormones). Those ribosomes in the cytoplasm make proteins that stay in the cell(replace organelles)
BIKINI

7. RNA

8. MAKING mRNA 1st step in protein synthesis
Messenger RNA is made in the nucleus in a process called: TRANSCRIPTION
“to write across”
Here the genetic code on DNA is “rewritten” in a strand of mRNA. m

9. Once the mRNA is formed it detaches from the DNA TEMPLATE, leaves the nucleus and enters the cytoplasm.
The DNA either closes or TRANSCRIPTION continues until enough mRNA is made for protein synthesis

10. Let’s Transcribe! Remember; NO ‘T’ in RNA! DNA
T A C C G C T A G C C C G C G T C T A A G T A C C T A A C T
mRNA
A U G G C G A U C G G G C G C A G A U U C A U G G A U U G A

11. Next Steps…. TRANSLATION
The newly formed messenger RNA leaves the nucleus
Together with the ribosomes and tRNA a new protein is formed during…
TRANSLATION
“ across languages”
In this process the base code ‘language’ of the nucleic acids is translated into the amino acid ‘language’ of protein

12. TRANSLATION USING mRNA TO CONSTRUCT A POLYPEPTIDE CHAIN OF AMINO ACIDS
TAKES PLACE IN RIBOSOMES(ROUGH E.R. OR CYTOPLASM)
The BASE CODE SEQUENCE that was TRANSCRIBED from DNA to mRNA determines the sequence of AMINO ACIDS which determines the NATURE OF THE PROTEIN
Now, Let’s see how the code is read…

13. MESSENGER RNA (mRNA) CODONS
THE GENETIC CODE IS TRANSLATED IN
‘3 LETTER WORDS”
On mRNA – THREE NUCLEOTIDE BASES FORM ONE CODON.
EACH CODON CODES FOR A SPECIFIC AMINO ACID

14. TRANSFER RNA – (tRNA) The Translator
THREE NUCLEOTIDES AT THE BOTTOM OF THE tRNA IS THE ANTICODON
THE ANTICODON ARE THE COMPLIMENTARY BASES ON THE mRNA CODON
THE TAIL OF THE tRNA CARRIES AN AMINO ACID THAT CORRESPONDS TO THE CODON.

15. THE RIBOSOME CELL ORGANELLE THAT IS MADE OF rRNA.
SITE OF PROTEIN SYNTHESIS
TWO PIECES
SMALL SUBUNIT ATTACHES TO THE mRNA
LARGE SUBUNIT DIRECTS tRNA
HAS 2 ‘PARKING PLACES’ FOR ONLY TWO tRNA AT A TIME

16. THE PROCESS OF TRANSLATION
STEP 1:
The small subunit attaches to mRNA at the start codon, always AUG
The large subunit attaches over the small subunit, encasing the mRNA strand
LARGE SUBUNIT
START CODON
mRNA

17. STEP 2
The first tRNA carrying the first amino acid, always Methionine, enters the ribosome and attaches to the start codon
The ribosome then shifts down one codon

18. STEP 3. The mRNA codon is ‘read’ by the ribosome and the second corresponding tRNA carrying the second amino acid enters
STEP 4. Once the second tRNA docks, a peptide bond is formed between the two amino acids
PEPTIDE BOND

19. The ribosome again shifts down one codon
STEP 5. The first tRNA releases its amino acid and leaves the ribosome.
The ribosome again shifts down one codon
STEP 6. This process of building the polypeptide chain continues until the ribosome reaches the STOP codon and detaches.
Many ppc’s are made continuously from one mRNA
ppc’s are processed into proteins by the Golgi body
POLYPEPTIDE CHAIN
Protein synthesis

20. READING THE AMINO ACID WHEEL
mRNA Codon
CAU
Start with
first letter
in center and
work your
way out for
each letter in
the codon until
you identify the
amino acid
OR CHART
HISTIDINE
READING THE AMINO ACID WHEEL
Match the codon with its amino acid
UCA AAC GCG GAC UUC
Serine
SER
Asparagine
ASP
Alanine
ALA
Aspartic acid
ASP A
Phenylalanine
PHY

21. What might this imply about certain amino acids?
There are only 20 amino acids(that is 20 monomers) for all proteins. However, there are far more than 20 codons. For example: Find LEUCINE( be careful, its listed more than once…how many codons are there for this one amino acid?
What might this imply about certain amino acids?
Amino acids that are used more often in proteins have more than one codon; this helps increase the rate of protein synthesis and decreases chance mutation will alter the protein. 6
Also, note that for many codons the last
base can be any of the 4. This also
decreases the chance that mutation will
alter the protein significantly.

22. Let’s Practice! Write the DNA sequence below onto the table;
TAC CTT AAC GAG CTA AAA GTT AGC TGG TTG ACT
Now, transcribe the mRNA codons from the DNA;
AUG GAA UUG CUC GAU UUU CAA UCG ACC AAC UGA
Good Job! Now, what would the tRNA anticodon’s be?
UAC CUU AAC GAG CUA AAA GUU AGC UGG UUG ACU
Awesome! Now, let’s make a polypeptide by translating the mRNA codon’s to amino acids:
MET- GLU A-LEU-LEU-ASP A-PHY-GLU-SER-THR-ASP-STOP

23. TRANSCRIPTION(nucleus)
REPLICATION
(nucleus)
TRANSCRIPTION(nucleus)
TRANSLATION(cytoplasm in RIBOSOME)

27. TRANSLATION

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