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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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