Chapter Eleven

Key Terms:
Gene Expression- the overall process of gene flow from genes to proteins
Operon- a group of genes under coordinated control in bacteria
Regulatory gene- codes for a repressor protein
Activators- enhance RNA polymerase binding to the promoter
Differentiation- involves cell specialization, in structure and function
Nucleosomes- formed when DNA is wrapped around histone proteins
Barr Body- inactivated X chromosome
Transcription factors- promote RNA polymerase binding to the promoter
Silencers- repressors that inhibit transcription
Homeotic genes- master control genes that determine the anatomy of the body

Reading Journal:
1) How does differentiation work? Differentiation works by turning specific sets of genes either on or off.
2) What is a lac operon? it is an active repressor that binds to the operator; the inducer, which is lactose, binds and inactivates the repressor.
3) What is a signal transduction pathway? it is a series of molecular changes that converts a signal at the cell's surface to a response within a cell.

Five facts:
1) Most differentiated cells retain a full set of genes, even though only a subset may be expressed.
2) Cloned animals can show differences from their parent due to a variety of influences during development.
3) Tumor-suppressor genes promote cancer when both copies are mutated.
4) Carcinogens are cancer-causing agents that damage DNA and promote cell division.
5) Cloning does not increase genetic diversity, but can be used to help save endangered species.


in prokaryotes, genes for related enzymes are often controlled together in units called operons. gene regulation can help organisms respond to environmental changes. regulatory proteins bind to control sequences in the DNA. In multicellular eukaryotes, cells differentiate, or specialize in a specific task. A chromosome contains DNA that goes around clusters of histone proteins, forming a string of beadlike nucleosomes. DNA packing sometimes block gene expression, preventing access of transcription proteins to the DNA. A variety of regulatory proteins interact with DNA and with each other to turn the transcription of eukaryotic genes on or off.
The lifetime of an mRNA molecule helps determine how much protein is made, as do protein factors involved in translation. A protein may need to be activated, and eventually the cell will break it down.
Gene expression controls the development of an animal from a fertilized egg. Signal transduction pathways convert molecular messages to cell responses. Some similarities in organisms have suggested the signal transduction pathways evolved early.
In cloning, a clone is an individual created by asexual reproduction and is genetically identical to a single parent. nuclear transplantation is used to clone animals. The goal of therapeutic cloning is to produce embryonic stem cells. Embryonic stem cells have not differentiated yet, thus they are more diverse with applications. In adult stem cells, they normally have a limited range of cell types.
Cancer cells divide uncontrollably, which result from mutations in genes. a mutation can change into an oncogene. An oncogene is a normal gene that promotes cell division and divide excessively. Cancer result form a series of genetic changes in a cell lineages. Reducing exposure to carcinogens and making other lifestyle changes can help reduce cancer risks.



Here is an illustration of cloning. An unfertilized egg's nucleus is taken out of the egg, and replaced with a cell to be cloned. Once they develop to a certain stage, they are implanted into the organism.










Youtube video on Gene expression:
http://www.youtube.com/watch?v=OEWOZS_JTgk