1. Gene expression involves the transcription of DNA's genetic code into mRNA and the subsequent translation of mRNA into proteins. 2. During transcription, the DNA double helix is unzipped and an mRNA copy is produced in the nucleus using RNA polymerase. 3. The mRNA copy is then used as a template during translation as ribosomes match tRNA anticodons to mRNA codons to assemble amino acids into proteins.

1. GENE
EXPRESSION 1:
RNA & Protein
Synthesis
ppt. by Robin D. Seamon

2. GENE EXPRESSION
• also called Protein Synthesis
• also called Transcription/ Translation

3. CHON P R O T E I N S
• Made of amino acids
• Linked by peptide bonds
Peptide
bonds
Amino acid

4. P R O T E I N S
• Made of amino acids
• Most Complex
• Meat, hair, blood, insulin
• SHAPE determines function
• CLASSES
• Structure
• Enzymes
• Hormones
• Antibodies
• …more
• food

5. • One GENE on a DNA strand codes for the
production of one polypeptide.
• In the finishing stages,
the chain will fold into
a specific shape that
determines the protein’s function
Peptide bonds
Genetic Code
RNA

6. GENE EXPRESSION BRIEF OVERVIEW:
• DNA in the nucleus has the code/instructions
• Ribosomes from the cytoplasm read the code
and copy it into a draft copy-RNA (so the
original copy isn’t messed up)
• Ribosomes create the finished product
(protein) from the draft copy
• Protein is sent to the ER & Golgi Body for
finishing touches and packaging
DNA  RNA  Protein

7. DNA  RNA  Protein
NUCLEUS
has the
code
RIBOSOMES
Read the
code &
copies it
finished
product

8. A Protein carries out a function for
the cell/body
example: hemoglobin: carries oxygen
Peptide
bonds
Amino acid

10. 1. DNA holds master copy of instructions in the
nucleus
2. DNA is split by enzyme, helicase
3. Transcription: DNA is read and copied by the
ribosomes into a strand of RNA (draft copy)
4. Original (master) DNA is put back together by
enzyme, amylase
5. Translation: ribosomes use RNA draft to produce
a functional protein
6. Protein goes to ER and Golgi body for finishing
touches & packaging
PROTEIN SYNTHESIS

11. enzyme: substance that acts as a catalyst to bring
about a specific biochemical reaction
• speeds up reactions by lowering
activation energy
• temperature important!
• REMEMBER: Shape determines function
REMINDER:

12. example:
helicase- breaks hydrogen bonds
Where did we learn hydrogen bonds were?

13. Helicase enzyme that breaks the hydrogen
bonds by which DNA base pairs are held
together.
helicase

14. matching base
pairs are
added
2 new strandsoriginal
strand

15. Polymerase enzyme that puts the DNA back
together
polymerase

16. NEW SEQUENCES ADDED TO RNA
RNA has the same nucleotides as DNA (with
ONE EXCEPTION) and so matchup to the split
end of the DNA
The EXCEPTION:
RNA has adenine, guanine, cytosine, & ?
What’s missing?
RNA has Uracil instead of Thymine

17. DNA Nucleotides RNA Nucleotides
A T A C T G A T A C T G
DNA strand 1
makes strand 2:
DNA strand 1
makes strand 2:
T A T G A C U A U G A C

18. RNA Nucleotides DNA Nucleotides

19. Compare: DNA vs RNA

20. DETAIL

21. Transcription-
• Occurs in the nucleus
• DNA unzipped by helicase
• RNA polymerase makes mRNA

22. RNA
DNA
RNA
polymerase
Adenine (DNA and RNA)
Cystosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
Transcription
makes a
complementary
strand of mRNA
NUCLEUS

23. mRNA = Messenger RNA
• Carries the “message” from the DNA to make a
protein
RNA
Ribose nucleic acid
DNA
deoxyribose nucleic acid

24. Codons- 3 letter messages
1 codon codes for one amino acid

25. The genetic code is universal- all life forms can read it!

26. Translation- mRNA leaves nucleus for the ribosomes
NUCLEUS
mRNA

27. Translation-
• tRNA- Transfer RNA
carries appropriate
amino acid for
matchup
• called an anticodon
• There are 20 different
tRNA’s for the 30
different amino acids

28. tRNA
with
anticodon
Ribosome
with mRNA
codon
UGG
A C C
MATCHES UP

30. Polypeptide
chain grows
as tRNA
anticodons
continue to
match and
bind with the
mRNA
codons

31. START codon- starts translation of the first amino
acid in the polypeptide chain
STOP codon- stops & seals the polypeptide chain

32. The genetic code is universal- all life forms can read it!

34. Endoplasmic Reticulum folds the protein
into its functional shape to be shipped to
the Golgi Body

35. Golgi body puts on
finishing touches &
packages the protein
for export from the
cell membrane

37. REVIEW
DNA  RNA  Protein
(mRNA & tRNA)

38. RNA
DNA
RNA
polymerase
Adenine
Cystosine
Guanine
Thymine
Uracil
Transcription
• In the
nucleus
• Ribosome
copies
DNA into
mRNA

39. Translation
• In the ribosomes
• tRNA anticodons
match to mRNA
codons
• Polypeptide chains
grow until STOP
codon is reached

41. DNA vs RNA
DNA RNA
Sugar deoxyribose ribose
Strand Double Single
Bases A,T,C,G A,U,C,G,
Length Long Short
Function
Carries
instructions*
Interprets
instructions
* Exception - RNA viruses