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2. Immagini e concetti della biologia Sylvia S. Mader
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

3. B3 - Regulation of Gene Activity
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

4. Prokaryotes control gene expression
In prokaryotes, some DNA-binding proteins can turn genes on and off.
An operon is a cluster of genes under the control of a single signal. It includes:
a regulator gene
a promoter
an operator
structural genes
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

5. Prokaryotes control gene expression
The lack operon is an inducible operon, when lactose is absent, the operon is turned off; when lactose is present, the operon is active.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

6. Eukaryotes control gene expression
Eukaryotic cells are specialized thanks to the activation/deactivation of certain genes.
Active genes in different cells
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

7. Totipotent cells
Totipotent cells have the ability to give rise to an entire organism. All plant and animal cells are potentially totipotent cells as the nucleus keeps a copy of all the genes needed for a new individual.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

8. Animal cloning Animals can be cloned using a donor diploid nucleus.
The aim of a reproductive cloning is to obtain a new organism, genetically identical to the original.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

9. Animal cloning
Desire of a therapeutic cloning is to obtain mature cells of various types for medical purposes.
Either embryonic stem cells or adult stem cells may be used in therapeutic cloning.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

10. Animal cloning Benefits
Reproductive cloning can help save endangered species.
Therapeutic cloning can provide valuable medical products and fight cancer.
Drawbacks
Donor mitochondrial DNA is not transmitted and the clone may undergo premature aging.
In clones, mutation rate is higher and anomalies in gene regulation occur.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

11. Eukaryotes gene control
In the nucleus DNA and histone proteins are organized into linear units called chromatin.
Before cell division chromatin condenses to form chromosomes.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

12. Eukaryotes gene control
The genes in highly condensed chromatin (heterochromatin) are not expressed.
Euchromatin consists of loosely condense chromatin whose genes are expressed.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

13. Transcription-regulating proteins
DNA-binding proteins regulate transcription in eukaryotes.
Transcription factors are proteins that help regulate transcription.
Transcription activators bind to specific regions of DNA (enhancer) and promote transcription.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

14. mRNA influences gene expression
Post transcriptional gene control occurs in the nucleus. It involves:
the primary mRNA splicing;
the speed at which mRNA leaves the nucleus.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

15. Cytoplasmic gene expression control
The last control of gene expression occurs in the cytoplasm during and after the translation.
Translational control begins when processed mRNA reaches the cytoplasm before the protein production.
Post-translational control begins once a protein has been synthesized and becomes active.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

16. Gene expression control review
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

17. Gene expression in development
In order to have a proper development, genes must be turned on and off in an exact sequence.
In Drosophila melanogaster some genes determine the development of both anterior/posterior body axes and body segmentation.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

18. Homeotic genes and apoptosis
Homeotic genes determine segmentation and which segment develops what body parts.
Homeotic genes contain homeobox, DNA sequence involved in anatomical development.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

19. Genetic mutations and cancer
Apoptosis (programmed cell death) is important in cancer control.
Proto-oncogenes, promote the cell cycle and inhibit apoptosis.
Tumor suppressor genes, protect the cell from the development of the cancer.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

20. Genetic mutations and cancer
Oncogenes and mutated tumor suppressor genes cause excess cyclin which stimulates the cell cycle and makes p53 unavailable so that apoptosis does not occur.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

21. Genetic mutations and cancer
Products of faulty genes interfere with signal transduction when cancer develops.
A stimulatory signal transduction pathway turns on a proto-oncogene whose products stimulates the cell cycle.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

22. Genetic mutations and cancer
When cancer occurs the products of an oncogene leads to overstimulation of the pathway and the cell cycle excellerates.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

23. Genetic mutations and cancer
An inhibitory signal transduction pathway turns on a tumor suppressor gene whose products inhibits the cell cycle.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

24. Genetic mutations and cancer
When cancer occurs, the product of a mutated tumor suppressor gene fails to turn on the pathway and fails to stop the cell cycle.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

25. Cancer development
Carcinogenesis is the development of a malignant tumor due to repeated mutations.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

26. Cancer development
Angiogenesis (formation of new blood vessels) provides nutrients to a growing tumor.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

27. Cancer development
Motile cells invade lymphatic and blood vessels, metastasis occur when new tumors form far from the original site.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

28. Cancer therapy
Cancer diagnosis includes a complete check of patient health, imagine diagnostics, blood and urine analysis, endoscopy.
Surgery of a cancer cell mass is useful only for solid tumors.
Chemotherapy is a cancer treatment that uses drugs to destroy cancer cells.
Radiotherapy uses high energy rays to destroy cancer cells.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012