Download 6D * Recognize that a gene expression is a regulated process.

6D – Recognize that a gene
expression is a regulated process.
What is a gene?
What do genes code for?
protein
What is gene expression?
Process of using the genetic code in a
gene to produce protein.
It occurs in two steps:
 Transcription
 Translation
DNA  mRNA  Protein Trait
Simple Gene Expression
https://highered.mheducation.com/sites/9
834092339/student_view0/chapter15/sim
ple_gene_expression.html
Learning Check
If your birthday comes before your
partner’s birthday, you are a partner A.
Partner A – YOUR JOB:
Explain in 15 sec the gene expression in
your own words to your partner.
Partner B – YOUR JOB:
In 15 sec, repeat what the partner A said
and add comments/corrections if needed.
Different proteins are needed by different
cells, which mean that different genes are
expressed in different cells.
All cells within an organism contain the
same DNA sequence, but not all genes
are used by all cells.
• Some genes are always
expressed.
• Other genes are not expressed
all the time and need to be
turned on and off at need as a
light switch – this needs to be
regulated.
Genes turned on determine cells’ function
Learning Check
Are all genes expressed (turned on) all the time?
NO, only the genes that the cell need are transcribed
into mRNA  protein  trait
Why is the gene expression need to be
regulated?
Because some genes need to be turned ON and OFF at
need.
Why do different cells have different functions?
Different genes are turned on in different cells 
different proteins are produced, which determine
different functions.
Gene expression is regulated by a cell.
Gene regulation is the ability of an
organism to control which genes are
transcribed in response to
environment.
Learning Check
7 sec - Find a different partner
In 10 sec, discuss the following with your partner:
What is being controlled when the gene
expression is regulated?
Gene regulation in prokaryotes:
An operon controls the transcription of
several genes at the same time in response
to changes in the environment.
The lac operon consists of three genes
(code for three enzymes) each involved in
processing the sugar lactose.
Lac = lactose
The lac operon (Amoeba Sisters):
https://www.youtube.com/watch?v=h_1QL
dtF8d0
E.coli can use either glucose as a
source of energy (monosaccharide) or
lactose (disaccharide). Lactose needs
to be hydrolyzed (digested) first, so
bacterium prefers to use glucose.
LACTOSE
No lactose
No enzymes needed to metabolize it =
no waste repressor binds to the
operator Blocks RNA polymerase 
NO transcription/translation  NO
protein (no enzymes)
The lac operon is turned on only when
glucose is absent, but lactose is
present.
Lactose present (enzymes are needed)
 Lactose binds to repressor and
changes its shape= Can’t bind to the
Operator  RNA Polymerase
transcribes genes into mRNA
translation  Enzymes are made to
break down lactose sugar for energy
Learning Check
How do the prokaryotes such as E. coli adapt to
the lack of food, glucose?
Turn on the genes (the lac operon) that code for
lactose synthesizing enzymes.
Gene regulation in eukaryotes (more complex)
Regulation occurs in all four stages:
Gene
1
2
3
4
What can affect this expression?
MUTATIONS
Many factors can affect the rate of
transcription and translation in living
cells including:
Changing in temperature or light; animals can change
color or grow thicker fur coats in the winter.
The presence or absence of nutrients in the environment;
lactose present triggers E. coli to produce specific lactose
synthesizing enzymes.