1. Section 14.3 Gene Expression and Regulation Part 1
This PowerPoint provides an overview of Prokaryotic and Eukaryotic Gene Regulation.
Students- do not only use this PowerPoint to study, you also have your notes to help you prepare.

2. Write down the function / definition of each of the following words:
Lac operon
Promoter
Operator
Repressor
RNA polymerase
Lactose
Transcription
Draw the picture in the top left corner of page 452.
Make sure your picture is labeled.

3. Write down the function / definition of each of the following words:
Draw the TOP picture on page 453.
Make sure your picture is labeled.
Gene expression
TATA box
RNA polymerase
Transcription factors
Enhancers
Cell specialization

4. Prokaryotic Gene Regulation
To conserve energy and resources, cells control which genes they express.
4288 genes code for proteins in E. coli
Example- cluster of 3 genes that must be turned on together before E. coli can break apart lactose (provides food for the bacterium)
3 lactose genes in E. coli = the lac operon
Operon = a group of genes that are regulated together

5. Prokaryotic Gene Regulation: Lac Operon
Lactose = galactose and glucose
Proteins coded for by the genes of the lac operon break down lactose
Environment with lactose = lac operon genes are transcribed
Environment without lactose = lac operon genes are NOT transcribed

6. Prokaryotic Gene Regulation: Promoters and Operators
Two regulatory regions:
Promoter (P)
Site where RNA polymerase binds to start transcription
Operator (O)
Site where a DNA-binding protein called the lac repressor can bind to DNA

7. Prokaryotic Gene Regulation: The Lac Repressor Blocks Transcription
When lactose is NOT present in the environment:
Lactose repressor binds to the operator (O) region
RNA polymerase cannot reach the genes to start transcription
The operon is “off”
E. coli does not need to transcribe the lac operon because lactose is not in the environment (so the cell does not need to make proteins to break it down)

8. Prokaryotic Gene Regulation: Lactose Turns the Operon “On”
When lactose IS present in the environment:
Lac repressor has a binding site for lactose
Lactose from environment enters cell and binds to lac repressor
Changes shape of repressor
Repressor falls off operator
RNA polymerase is now able to bind to promoter to start transcription
The operon is “on”
E. coli will transcribe the lac operon because lactose is in the environment (so the cell will make proteins to break down lactose)

9. Eukaryotic Gene Expression
More complex
Example- TATA box
Short regions of DNA (25-30 base pairs) before the start of a gene
Binds a protein that helps position RNA polymerase by marking a point just before the beginning of a gene

10. Eukaryotic Gene Regulation: Transcription Factors
DNA-binding proteins
Control the expression of genes by binding DNA sequences in the regulatory regions
Examples:
Open up tightly packed chromatin to attract RNA polymerase to start transcription
Block access to certain genes (similar to prokaryotic repressors)

11. Eukaryotic Gene Regulation: Transcription Factors
Can activate many genes at once  dramatically affecting patterns of gene expression
Example- Steroid hormones
Steroid hormones are chemical messengers that enter cells and bind to receptor proteins
These hormone-receptor complexes act as transcription factors that bind to DNA and activate multiple genes

12. Eukaryotic Gene Regulation: Cell Specialization
Most cells in a multicellular organism have the same DNA
Complex gene regulation:
Allows cells to be differentiated / specialized
Allows a zygote to develop into a functioning multicellular organism

13. Happy Wednesday  You need: Reminders: Hox gene half-sheet Notes
Pen or pencil
Reminders:
Quiz Friday- 2nd half of Section 14.3 AND all of Section 14.4
Notes due Tuesday- Section 12.4 in yellow book

14. Section 14.3 Gene Expression and Regulation Part 2
Students- do not only use this PowerPoint to study, you also have your notes to help you prepare.

15. Genetic Control of Development
Regulating gene expression is especially important during the earliest stages of development.
The activation of genes in different parts of an embryo causes cells to differentiate.

16. Homeotic Genes
Example- a specific group of genes controls the identities of body parts in the embryo of the common fruit fly
Change one of these genes, and a part intended to be one body part could develop into a another body part.
Homeotic genes (master control genes)- regulate organ development
Master control genes are like switches that trigger particular patterns of development and differentiation in cells and tissues.

17. Homeotic Genes
Homeotic genes share a very similar 180-base DNA sequence, called the homeobox.
Homeobox genes- code for transcription factors that activate other genes important in cell development and differentiation.
Hox genes-
Arranged from top to bottom (head to tail)
In fruit flies- determine each body segment
In humans- tell the cells of the body how to differentiate as the body grows

18. Homeotic, Homeobox, and Hox Genes
Homeotic genes regulate organ development.
Homeobox genes code for transcription factors.
Hox genes determine the identities of each body segment.
Tell students: The work of American biologist Edward B. Lewis made it clear that a set of master control genes, known as homeotic genes, regulate body parts that develop in specific parts of the body.
Click to display the summary point.
Explain that the molecular studies of homeotic genes show that they all share a very similar 180-base DNA sequence, which was given the name homeobox. Homeobox genes code for transcription factors that activate other genes that are important in cell development and differentiation.
Point out that, in flies, a group of homeobox genes known as Hox genes are located side by side in a single cluster. Hox genes determine the identities of each segment of a fly’s body.
Ask: What section of the bodies of flies and mice is coded by the genes shown in blue?
Answer: the back of the body; posterior portion of the abdomen of the fruit fly and rump of the mouse

19. Epigenetics
When chromatin is tightly packed…gene expression is blocked.
When chromatin is opened up…gene expression is enhanced.
Cells regulate chromatin by enzymes that attach chemical groups to DNA and histones:
Methyl groups (--CH3) will cause chromatin to condense, blocking transcription.
Acetyl groups (--CO-CH3) will open chromatin up for transcription and gene expression.

20. Epigenetics Epigenetics- above the level of the genome
Epigenetic marks do not change DNA base sequences.
They influence patterns of gene expression over long periods of time.

21. Environmental Factors
Temperature
Salinity
Nutrient availability
Insufficient nourishment during the first three months of pregnancy