1. Chapter 8: From DNA to Protein Section 8.4 - Transcription

2. What do we know so far? DNA Proteins I get it!!! DNA is like
DNA is the genetic information
Located in Nucleus (protected in vault)
Proteins
all living things made of proteins
Proteins made by ribosomes in cytoplasm
proteins run living organisms
example – enzymes
So the DNA molecule
is the instructions
for making proteins!!!
I get it!!!
DNA is like
a blueprint!!

3. But there is a problem……….
Need to get the blueprint information (DNA message) from nucleus to cytoplasm
We need
mRNA!!!!
We need
a messenger

4. DNA RNA mRNA Who is the mRNA messenger? build proteins messenger RNA
nucleus
cytoplasm

5. The “Central Dogma” – information flows in one direction
transcription
DNA
mRNA
protein
translation
trait
(phenotype)
cell cytoplasm
cell nucleus

6. You have to know differences between DNA and RNA for my test and EOC!!!!
ribose sugar
nitrogen bases
G, C, A, U
U = uracil
U : A
C : G
single stranded
DNA
deoxyribose sugar
nitrogen bases
G, C, A, T
T = thymine
T : A
C : G
double stranded

7. Transcription is making mRNA from DNA
Double stranded DNA unzips by helicase enzyme T G G T A C A G C T A G T C A T C G T A C C G T

8. Transcription is making mRNA from DNA
Now that DNA is unzipped; enzyme RNA polymerase attaches base pairs T G G T A C A G C T A G T C A T C G T A C C G T

9. Transcription is making mRNA from DNA
RNA polymerase will match RNA bases to DNA bases on one of the DNA strands
Notice NO THYMINE!!!!!!! C U G A G U G U C U G C A A C U A A G C
RNA
polymerase U A G A C C T G G T A C A G C T A G T C A T C G T A C C G T

10. TACGCACATTTACGTACGCGG AUGCGUGUAAAUGCAUGCGCC
Transcription is making mRNA from DNA
U instead of T is matched to A in mRNA
TACGCACATTTACGTACGCGG
DNA
AUGCGUGUAAAUGCAUGCGCC
mRNA
Once mRNA molecule is completed it leaves nucleus and goes to cell cytoplasm

11. Chapter 8: From DNA to Protein
Section Translation

12. DNA
instructions remain in nucleus and we have to send message out
mRNA
has the instructions for building proteins from DNA
nucleus U C A G

13. Proteins are built as chains of amino acidsaa
Proteins are built as chains of amino acids
What reads RNA?
need a mRNA reader!

14. Now lets look at bigger picture!!!
RNA to protein
mRNA leaves nucleus
mRNA goes to ribosomes in cytoplasm
amino acids are linked bc of mRNA message
proteins built from sequence of amino acids
Now lets look at bigger picture!!!
mRNA A C C A U G U C G A U C A G U A G C A U G G C A aa aa aa aa aa aa aa aa

15. RNA to protein bigger picture
Cell cytoplasm aa
transcription
translation
DNA
mRNA
protein
ribosome
mRNA leaves nucleus through nuclear pores U C A G
proteins synthesized by ribosomes using instructions on mRNA
trait
Cell nucleus

16. How does mRNA code for proteins?
TACGCACATTTACGTACGCGG
DNA
AUGCGUGUAAAUGCAUGCGCC
mRNA
think letters
in alphabet ?
protein
How can you code for 20 amino acids with only 4 nucleotide bases (A,U,G,C)?

17. mRNA codes for proteins in triplets
TACGCACATTTACGTACGCGG
DNA
codons
ribosome
AUGCGUGUAAAUGCAUGCGCC
mRNA
AUGCGUGUAAAUGCAUGCGCC
mRNA
Met Arg Val Asn Ala Cys Ala
protein
Ribosomes read mRNA in blocks of 3 nucleotides called a “Codon”

18. How are the codons matched to amino acids?
DNA
TACGCACATTTACGTACGCGG
AUGCGUGUAAAUGCAUGCGCC
mRNA
UAC
Met
GCA
Arg
CAU
Val
tRNA
anti-codon
amino acid

19. The mRNA code Start codon Stop codons AUG UGA, UAA, UAG codon for
methionine (Met)
leucine (Leu)
Strong evidence for a single origin in evolutionary theory.

20. Summarize whole process of “DNA to Proteins”aa
transcription
translation
DNA
mRNA
protein
ribosome
tRNA aa U C A G
trait
Cell nucleus
Cell cytoplasm

21. Different view of “DNA to Proteins”
Cell cytoplasm
transcription
translation
protein
Cell nucleus
trait

22. DNA transcription mRNA ribosome translation
amino acids
mRNA
protein
ribosome
tRNA
translation

23. Section 8.6:
Gene Expression and
Gene Regulation

24. The BIG Questions…
How are our traits turned “on” or “off”?

25. How do cells control Gene Expression?
Cells turn genes “on” & “off” by controlling transcription
Remember what RNA Polymerase did?

26. How do cells control Gene Expression?
For RNA Polymerase to do its job it has to attach to the DNA molecule
Promoter - area of DNA where RNA polymerase binds. Also area where the “Gene” sequence begins.
Operator – area of DNA that turns gene “on” or “off”. It’s the switch
Lets take a closer
look at how this
works!

27. Gene regulation using “lac Operon Model”
The lac Operon uses a repressor protein as a stop sign until gene is ready to be made

28. Do you want all your genes turned on if you just need to make one trait? NO!!!!!
Eukaryotic RNA is processed before leaving nucleus. “RNA Splicing”
Introns – gene segments that are cut out before mRNA leaves nucleus
Exons – gene segments that attach to each other that will code for mRNA

29. http://www. pbslearningmedia. org/resource/tdc02. sci. life. gen