Gene Expression/ Protein Synthesis

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

2. VIDEO: Why RNA is Just as Cool as DNA

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

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

5. 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

6. VIDEO Protein Synthesis 1
VIDEO: Protein Synthesis 2

7. • 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

8. 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

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

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

12. 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

13. 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:

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

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

16. Polymerase enzyme that puts the DNA back
together

17. 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

18. 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

19. RNA Nucleotides DNA Nucleotides

20. Compare: DNA vs RNA

21. DETAIL

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

23. 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

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

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

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

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

28. Translation-
• tRNA- Transfer RNA
carries appropriate
amino acid for
matchup
• called an anticodon

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

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

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

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

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

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

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

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

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

42. 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

44. VIDEO: Mutations

45. Mutations: a change in the coding of a gene
-can occur through:
1. Deletion: cell accidentally omits a piece of the
DNA
2. Duplication: cell accidentally makes an extra
copy of the DNA piece
3. Insertion: cell accidentally adds a piece of
DNA
4. Translocation: cell accidentally puts a piece of
genetic sequence in the wrong place.
45

46. ACTIVITY
• THE OLD RED DOG WAS TOO BIG FOR HIS BED
• Deletion that would delete the D in OLD…
• THE OLR EDD OGW AST OOB IGF ORH ISB ED
• Inversion of the word DOG...
• THE OLD RED GOD WAS TOO BIG FOR HIS BED
46
FRAME SHIFT- confuses the
whole message: bad mutation
less of a problem

47. mutation example:
• one mutation in the gene for hemoglobin
(change T to A) causes sickle cell anemia