Warm up  1. How is DNA packaged into Chromosomes?  2. What are pseudogenes?  3. Contrast DNA methylation to histone acetylation (remember the movie “Ghost in your Genes”?)

Warm up  1. Why are transposons important in genetics?  2. How and why do cells differentiate?  3. Draw a Eukaryote gene (p th ed)

Control of Eukaryotic Genome-ch19 Eukaryotic chromosomes are much more complex than the single circular chromosome found in prokaryotes. These chromosomes are made of DNA and a complex of proteins. This material is called chromatin. DNA from a growing salamander ovum.

Chromatin structure is based on levels of DNA packing. 1. Protein histones wind DNA into nucleosome beads 2. Nucleosome beads coil and fold up with the help of other proteins that act as scaffolds 3. Chromosomes form for meiosis and mitosis.

Genome Organization at the DNA Level Tandem DNA= repeating short patterns of DNA nucleotides; has a different density than regular DNA and forms a “satellite” bands when centrifuged. Fragile X is a mutation where an extremely long tandem of repeating triplets of CGG results in mental retardation

Gene families have evolved by duplication of ancestral genes Hemoglobin is a protein with quaternary structure. Made of four globular proteins These duplicated genes are called multigene families There are many repeats of this protein in human DNA, similar but not identical. They turn on and off at different times. They can all be traced back to an individual protein.

Gene amplification can add extra sources of mRNA when needed, as in a developing embryo. Re-arrangement can alter a cell's genome A transposon can knock out a gene by copying into its middle, or turn one on or off permanently by knocking out a regulatory gene.

The Control of Gene Expression Each eukaryotic cell expresses only a small fraction of its genes. Differentiation determines which genes turn on and off as an embryo develops. The control of gene expression can occur at any step in the pathway from gene to functional protein.

Chromatin modifications= affect the availability of genes for transcription. Epigenetic changes do not affect the sequence of the code, only the reading of the code DNA methylation = deactivates sections of a chromosome (Barr bodies in females); Histone acetylation = attaches an acetyl group to activate transcription.

A Eukaryotic Gene Transcription initiation is controlled by transcription factors. These factors bind to the promoter region of the gene.

Control of Transcription Initiation Close to the promoter are control elements, and another set of control elements called enhancers further upstream of the gene.

Activators attach to the enhancers. Together with initiation factors that binds to the TATA end of a promoter, a site for RNA polymerase binding forms. The DNA bends and helps hold together the transcription factors. This creates a transcription initiation complex that allows RNA polymerase to bind.

. Processing of mRNA introns and exons in different ways can control protein production, especially by adding regulatory sites. Proteins can also be controlled. Once tagged by ubiquitins, proteins are marked for degradation.

The Molecular Biology of Cancer Cancer results from genetic changes that affect the cell cycle. Proto-oncogenes promote normal cell growth. These three changes can cause proto-oncogenes to become full-fledged cancer-causing oncogenes.

Oncogene proteins with faulty tumor-suppressor proteins can interfere with normal signaling pathways. The ras protein plays a vital role in controlling cell growth. If it is transformed into a hyperactive state, cell growth is overstimulated. An initiation factor called p53 inhibits cell growth. If it becomes defective the growth inhibiting protein is not made.

Multiple mutations underlie the development of cancer Combinations of the loss of tumor supressors with the addition of hyperactive oncogenes results in cancerous tumors.