Gene Expression
Breaking Down the Definitions--Honors
1. Gene expression
2. Genome
3. Structural gene
4. Operator
5. Operon
6. Lac operon
7. Repressor protein
8. Regulator gene
9. Inducer
10. Euchromatin
11. Intron
12. Exon
13. Pre-mRNA
14. Transcription factor
15. Enhancer
16. Cell differentiation
17. Homeotic gene
18. Homeobox
19. Proto-oncogene
20. Tumor
21. Cancer
22. Tumor-suppressor gene
23. Metastasis
24. Carcinogen
25. Carcinoma
26. Sarcoma
27. Lymphoma
28. leukemia
Breaking Down The Definitions—Regular Bio
1.
2.
3.
4.
5.
6.
7.
Cancer
Mutation
Operon
Operator
Differentiation
Hox gene
Genome
Control of Gene Expression
•GENE EXPRESSION is the activation or
‘turning on’ of a gene for transcription and
mRNA.
•Not all proteins are required by cells at all
times so the cell as the ability to control
when each protein is made.
Gene Expression in Prokaryotes
• E. Coli (bacteria in mammal intestines) were studied
in great detail
• Structural Genes—are genes that code for
polypeptide chains, a final product such as a protein
• A Promoter– is an enzyme that helps RNA begin
transcription
• An Operator is a DNA segment that controls the
ability of RNA polymerase to move along the
structural gene.
Structural
Gene
Promoter
Operon
Operator
Operon
•An Operon is a series of genes that code
for specific products.
•Lac Operon is a series of genes that code
for lactose metabolism in E. Coli.
Turning it On/Off
• A REPRESSOR PROTEIN is a protein that inhibits genes
from being expressed…it blocks the advancement of
RNA polymerase and stops transcription. So if the
Repressor Protein is present, the operon is turned
OFF.
• An INDUCER is a molecule that starts gene expression.
Inducers can be many things…in E.Coli, lactose acts as
the inducer. When lactose is present, the operon is
turned ON and can produce proteins.
Operon Video Clip
Gene Expression in Eukaryotes
• Eukaryotic cells are more complex, larger, and
contain more genes than prokaryotes
• When the DNA is NOT coiled in X-shaped
chromosomes (during cell division), it is called
EUCHROMATIC and is where transcription
occurs.
• DNA in Eukaryotes has a promoter and also
INTRONS and EXONS.
Gene Expression in Eukaryotes cont.
• INTRONS are sections of the structural gene that
are transcribed but not translated.
• EXONS are the sections of a structural gene that
when expressed are transcribed and translated.
• There is currently a lot of research being done
with Introns and Exons…
Gene Expression in Eukaryotes cont.
• After transcription in the nucleus both Introns
and Exons have been transcribed resulting in a
large molecule knows as pre-mRNA.
• Pre-mRNA is a form of mRNA that has both
Introns and Exons.
• mRNA is formed after the Introns are removed
(now the mRNA has only Exons)
Pre-mRNA to
mRNA
DNA is transcribed into
pre-mRNA
Introns are removed
Exons are spliced together
forming mRNA.
mRNA travels to Ribosome
for translation
RNA Splicing Video
Quick Lab (p.221)
1. Write a sentences that contains only 3 letter words. (at least 5
words)
a. “The cat ate the bat.”
2. Hide the words in a long sequence of letters, both random, and
with other words.
a. ATRCTHEGBPXAPELOCATFRATENMPHATTTHEDQWBATFESTOO
3. Trade papers with another group and cut/tear out the “introns”
a. THE CAT ATE THE BAT
b. The remaining letters and words “Exons”, are spliced or put together and
move on to the ribosome.
Gene Control in Eukaryotes
•Like prokaryotes, gene control takes place in
transcription, but instead of repressors, they
use TRANSCRIPTION FACTORS (same type of
thing; more complex)
Gene Expression in Development
• As eukaryotic creatures grow, control of gene
expression allows certain traits to be developed
and others to be ‘turned off’ until needed.
• HOMEOTIC GENES are regulatory genes that
determine where certain anatomical structures
(such as appendages) will develop and when.
• HOMEOTIC GENES are the ‘master genes’ and
know how to organize the organisms overall
body.
Cell Division
• PROTO-ONCOGENES are genes that regulate cell division;
ensuring that cell division occurs in the proper sequence and at
the correct rate.
• A mutation of a proto-oncogene can change the gene into a
ONCOGENE, which causes uncontrolled cell growth.
• A TUMOR is an abnormal growth of cells that is uncontrolled.
• A BENIGN TUMOR causes no threat to life (the uncontrolled cells
stay in the mass) unless it presses on vital organs in which case is
can be surgically removed.
• A MALIGNENT TUMOR cell’s invade and destroy healthy tissue as
it grows uncontrollably. This is called CANCER.
Cell Division Cont.
• Some genes act as ‘brakes’ to suppress tumor
formation= TUMOR-SUPPRESOR GENES code for
proteins to prevent cell division from occurring
too quickly or too often.
• In cancer these ‘brakes’ are often damaged.
Causes of Cancer
• Mutations may occur in the genetic code that
result in cancer.
• More likely, the organism is exposed to a
CARCINOGEN or a substance the induces cancer
• CARCINOGENs are also called MUTAGENS, an
agent that causes mutations to occur in the cells.
• Well Known carcinogens—tobacco smoke,
asbestos, radiation, some viruses
Introduction to Cancer Biology