Regulating Gene Expression

Reviewing Vocab…

• GENE: a segment of DNA that codes for a particular protein/trait

• An expressed gene is one that is being transcribed (i.e. it is turned to the “on” position and is being used to make proteins!)

• A repressed gene is one that is not being transcribed (i.e. it is turned to the “off” position)

How do we turn genes on and off?

Demonstration

• Observe the two DNA models – can you identify the histones?

• What is different about the two models?

Video

• http://learn.genetics.utah.edu/content/epigenetics/intro/

Vocabulary

• Epigenome

• Epigenetic Tags

• What do these do to the physical structure of DNA?

• What kinds of things shape your epigenome?

DNA structure and Regulation

• http://learn.genetics.utah.edu/content/epigenetics/control/

• Watch what happens to the appearance of the DNA, the # of mRNA, # of proteins, and the appearance of the cell as you turn the knob.

TRUE OR FALSE? METHYL AND ACETYL GROUPS CONTROL GENE EXPRESSION BY CONTROLLING ACCESS TO DNA.

TRUE OR FALSE? THE PHYSICAL STRUCTURE OF DNA IS STATIC.

Lick your rats

• http://learn.genetics.utah.edu/content/epigenetics/rats/

So what does this have to do with protein synthesis?

• http://www.teachersdomain.org/asset/biot09_vid_epigenetics/

• http://www.pbs.org/wgbh/nova/teachers/body/epigenetics.html

• http://www.pbs.org/wgbh/nova/body/epigenetics.html

30,000+ genes

• Does each cell need to be using all 30,000 genes? (hint: cell specialization!)

• Do you need to be using all 30,000 genes at all times? (hint: energy conservation!)

Regulation

• “Controls” over gene expression• Variety of methods– One basic way is by modifying the structure of

DNA

Epigenetics

• http://learn.genetics.utah.edu/content/epigenetics/intro/

Epigenetics

The development and maintenance of an organism is orchestrated by a set of chemical reactions that switch parts of the genome off and on at strategic times and locations.

• Epigenetics is the study of these reactions and

the factors that influence them.

For example…

• Genes that control whether or not a cell gets to go through mitosis…– regularly turned on and off = cells only divide

when needed.– Cancer cells = unregulated cell division =

epigenetic profile looks different…

Epigenetic Tags

• Acetyl and methyl groups• Chemicals that act as switches that determine

gene expression without changing the underlying genetic code

• Turn genes on or off in response to cell signals• Create a layer of control called the epigenome

Epigenome

• Reacts to factors throughout your lifetime.• Can affect future generations too…

Regulation of Genes

• Genes can be turned on or off• Off = not active, not making proteins– Tightly wound– DNA covered in methyl groups

• On = active, making proteins– Not tightly wound– Acetyl groups attached to histones

Other ways to control gene expression…

• Introns vs exons• Activity -

• http://www.youtube.com/watch?v=9k_oKK4Teco