Chapter 11 - How Genes are Controlled

Q: How is it that densely packed DNA prevents gene expression?
A: RNA polymerase and other proteins necessary for transcription do not have viable access to DNA that is tightly packed.
Q: How is alternative RNA splicing used to enable a single gene that will encode more than one kind of polypeptide?
A: A polypeptide is encoded by a mRNA molecule that contains different combinations of exons.
Q: What can be learned from a DNA microarray?
A: In a DNA microarray it can be inferred what genes are active in a particular sample of cells.

Five main facts:
1) Proteins that interact with DNA turn prokaryotic genes on or off in response to outside changes such as environment.
2) Differentiation can result from the expression of many combinations of genes.
3) DNA packing in eukaryotic cells help regulate how genes will be expressed.
4) Eukaryotic RNA can be spliced in several different ways.
5) In the later stages of translation, gene expression may be subject to regulation.

This diagram shows the packing of DNA into a chromosome. It shows how spacers are used to keep genes from interfering with one another. 

In chapter 11 the main focus is how genes are expressed. There is a control in both prokaryotic and eukaryotic cells. This allows for certain genes to be expressed that will benefit an organism. Also the cloning fo plants and animals is talked about and can be regulated by scientists through differentiated cells and nuclear transcription. 

Key Terms:

1) Differentiation: when cells become specialized in structure and function

2) Histones: association of the DNA with small proteins

3) Barr body: the inactive X in each cell of a female condenses into this compact object

4) Transcription factors: assistance given from proteins in order for eukaryotic RNA to function

5) Enhancers: binding of activator proteins to DNA sequences 

6) Silencers: proteins that may bind to DNA sequences and inhibit the start of transcription

7) RNA interface: procedure in which researchers can take advantage of miRNA mechanisms to artificially control gene expression

8) Hometic gene: master control gene that regulates batteries of other genes that actually determine the anatomy of parts of the body

9) DNA microarray: glass slide with thousands of different kinds of single-stranded DNA fragments fixed to it in a tightly spaced array or grid

10) Adult stem cells: cells that are able to give rise to many but not all cell types in an organism 

http://www.youtube.com/watch?v=mUcE1Y_bOQE