Chapter 15  -- CONTROLS OVER GENES

1. Textbook website: http://www.brookscole.com/biology
   1. chapter by chapter resources
      1. chapter/outlines/ch15.html
      2. chapter/quizzes/ch15
      3. flash cards-select from resources for chapter 15.
2. On-Line Biology Book by M. J. Farabee 
   1. Control of Gene Expression
3. Kimball's Biology Pages
   1. The Operon from Kimball's Biology Pages
   2. Gene Regulation in Eukaryotes from Kimball's Biology Pages
   3. X inactivation
   4. Cancer
   5. Cancer: The Causes and Prevention of Cancer as described by Bruce Ames, who has
      studied these questions for many years 
   6. Oncogenes
   7. Apoptosis
4. The Biology Project  an interactive online resource for learning biology, developed at The University of Arizona
   1. Molecular Genetics of Prokaryotes
   2. Eukaryotic Gene Expression
5. MIT Biology Hypertext 
   1. Prokaryotic Genetics and Gene Expression
      1. Studying Prokaryotic genes
      2. Lac operon
      3. other regulated sysytems
6. North Harris College Gene Regulation
7. Mendel Web

CONTROLS OVER GENES Chapter 15 

When DNA Can't Be Fixed 

1. Normal cells have the ability to turn genes on or off 
2. Cancer is a failure in genetic control caused by changes in DNA  [e.g., malignant melanoma, fig. 15.1] 

15.1 – OVERVIEW OF GENE CONTROL 

15.2 – GENETIC CONTROL IN PROKARYOTES 

Regulation of Gene Expression 

1. Operon: regulated cluster of associated structural genes with related functions [15.4]
   1. promoter site: for binding RNA polymerase 
   2. operator site:  shuts off DNA synthesis if occupied by repressor 
   3. structural gene(s): section(s) that codes for a polypeptide (but not a repressor) 
2. regulatory gene: produces repressor substance

Negative Control of Transcription 

1. A. feedback inhibition (negative feedback)
   1. the Lac (Lactose) Operon [fig. 15.4]
2. Positive Control of Transcription 
   1. catabolite activator protein (CAP) 
   2. cyclic AMP binds to CAP
   3. when glucose is scarce, the CAP-cAMP complex forms and promotes the binding of RNA polymerase to the lac operon

15.3 – GENETIC CONTROL IN EUKARYOTES [fig 15.5]

Cell Differentiation and Selective Gene Expression 

1. Transcriptional Control
   1. gene amplification
   2. DNA rearrangements
   3. Chemical Modification
      1. chromosome structure: histone interactions [Fig. 15.7]
      2. activators (e.g., promoter elements)
   4. overlapping transcriptional units
2. Transcript Processing Controls
   1. alternative splicing of introns and exons
3. G. Translational Control 
   1. stability of mRNA
   2. Transport Control: control over rate mature mRNA is shipped to cytoplasm 
4. Posttranslational control 
   1. feedback inhibition 
   2. modification of protein structure (shape, addition of functional groups)

15.4 – EVIDENCE OF GENE CONTROL 

Transcription in Lampbrush Chromosomes [fig 15.6, 15.7]

X Chromosome Inactivation 

1. Dosage Compensation for XX vs XY
2. Barr bodies: dark staining inactivated X [fig 15.8a]
3. mosaic tissue effect (Lyonization)
   1.   anhidrotic ectodermal dysplasia [fig. 15.9b]
4. Calico cats [fig. 15.9]

15.5 – EXAMPLES OF SIGNALING MECHANISMS 

Hormonal Signals

1. Steroid Hormones
2. enhancers
3. polytene chromosomes [fig 15.10] in salivary glands of insect larvae
4. vertebrates
   1. some hormones have widespread effects (e.g., somatotropin)
   2. other are specific (e.g., prolactin). 

Sunlight as a Signal [fig 15.11]

1. phytochrome

15.6 – GENES IMPLICATED IN CANCER

1. protein kinases
2. growth factors
3. characteristics of cancer cells
4. apoptosis

KEY TERMS FOR CHAPTER 15

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