1. From Gene to Protein
How Genes Work

2. Typical eukaryotic animal cell
Where are proteins made?
Where is DNA?

3. aa
From gene to protein- The “Central Dogma” of biology “Flow of genetic information in a cell”
nucleus
cytoplasm
transcription
translation
DNA
mRNA
protein
ribosome
trait

4. DNA RNA RNA-ribonucleic acid ribose sugar instead of deoxyribose
Nitrogenous-bases
uracil instead of thymine
U : A
C : G
single stranded
RNA leave the nucleus
lots of different RNAs
mRNA, tRNA, and rRNA
transcription
DNA
RNA

5. Transcription Occurs in the: Converts DNA to m-RNA (messenger)
Nucleus of eukaryotic cell
Cytoplasm of prokaryotic cells
Converts DNA to m-RNA (messenger)
Occurs when cells need ___________
DNA can’t leave the nucleus
Must get the genetic code to a ribosome in the cytoplasm where proteins are made
Read

6. Transcription build RNA 53 Making mRNA from DNA
Transcription
Making mRNA from DNA
RNA polymerase will unzip DNA and form a transcription bubble
transcribed DNA strand = template strand
Un-transcribed DNA strand = coding strand
same sequence as RNA
enzyme
RNA polymerase adds one complimentary nucleotide at a time until the end of the gene is reached
Transcribes in a 5’ to 3’ direction
coding strand 3 A G C A T C G T 5 A G A A A G T C T T C T C A T A C G
DNA T 3 C G T A A T 5 G G C A U C G U T 3 C
unwinding G T A G C A
rewinding
mRNA
RNA polymerase
template strand
build RNA 53 5

7. Compare DNA and RNA
DNA RNA

8. Transcription practice
Transcribe the following DNA templates

9. When cells transcribe DNA into a mRNA molecule there is a problem.
Warm-up
When cells transcribe DNA into a mRNA molecule there is a problem.
Is this mRNA molecule ready to be translated at the ribosome? What do you think the problem is?

10. Eukaryotic genes have INTRONS-junk!
Eukaryotic genes are not continuous
exons = the real gene
expressed / coding DNA
introns = the junk
In-between sequence
introns come out!
intron = noncoding (inbetween) sequence
eukaryotic DNA
exon = coding (expressed) sequence

11. Removing the INTRONS! Forms a spliced mRNA with NO introns
mRNA splicing:
Process of removing introns from pre-RNA
Occurs after transcription
Forms a spliced mRNA with NO introns
Exons only
intron = noncoding (inbetween) sequence
eukaryotic RNA is about 10% of eukaryotic gene.
~10,000 bases
eukaryotic DNA
exon = coding (expressed) sequence
transcription
pre-mRNA
After splicing- no introns
~1,000 bases
spliced mRNA

12. RNA splicing enzymes Spliceosome Enzyme made of several snRNPs
recognize splice site sequence on pre-mRNA
cut & paste
removes introns
Forms spliced mRNA transcript
snRNPs
exon
intron
snRNA 5' 3'
spliceosome
exon
excised
intron 5' 3'
lariat
mature mRNA
intron
No, not smurfs!
“snurps”