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2. Immagini e concetti della biologia Sylvia S. Mader
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

3. B4 - Regulation of Gene Activity
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

4. Virus in genetics
Bacteriophages reproduce inside bacteria and show two different life cycles: lytic and lysogenic cycle.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

5. HIV and AIDS
HIV is the cause of AIDS and, as many other viruses, uses reverse transcription (from RNA to DNA) to insert a copy of its genome into the host genome.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

6. Bacteria in genetics Bacteria can exchange genes by:
Transformation (bacteria pick up external DNA)
Conjugation (DNA exchanges via sex pilus)
Transduction (DNA exchange via viruses)
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

7. 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, 2018

8. 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, 2018

9. 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, 2018

10. 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, 2018

11. 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, 2018

12. 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, 2018

13. 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, 2018

14. 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, 2018

15. Gene expression control review
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

16. 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, 2018

17. 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, 2018

18. Development genetics and speciation
Eyes development, limb development and shape determination are controlled by the same genes in different headed animals.
Pax6 gene is involved in the eyes development of many different animals
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018

19. Evolution
Differential gene expression can cause dramatic changes in body shape and organs.
Differential gene expression and/or new functions for old genes can explain evolution, including human evolution.
Sylvia S. Mader, Concepts of Biology © Zanichelli editore, 2018