Slide 1

Slide 2

2.e.1 Timing and coordination of specific events are necessary for the normal development of an organism, and these events are regulated by a variety of mechanisms (18.2-18.4). 3.b.1 Gene regulation results in differential gene expression, leading to cell specialization (18.1-18.3). 3.b.2 A variety of intercellular and intracellular signal transmissions mediate gene expression (18.1- 18.4). 4.a.3 Interactions between external stimuli and regulated gene expression result in specialization of cells, tissues, and organs (18.4).

Slide 3

Some bacteria can regulate their gene expression based on their surroundings E. coli needs tryptophan to survive; if it isnt getting trp from its environment (such as the human colon), then it makes its own When the host is ingesting enough trp for the E. coli, the bacteria inhibits enzyme activity thereby shutting down the synthesis of trp and conserving energy.

Slide 4

Fig. 18.2, page 352 An operon includes the operator (which controls the access of RNA polymerase to the genes), the promoter (a site where RNA polymerase can bind to DNA and begin transcription), and all the genes they control

Slide 5

Using trp synthesis as an example: The trp operon is turned on meaning that RNA polymerase can bind to the promoter and transcribe the genes of the operon The trp repressor switches the operon off, and the repressor binds to the operator blocking attachment of RNA polymerase to the promoter preventing gene transcription Fig. 18.3, page 353

Slide 6

3 billion base pairs ~30,000 genesgenes Total of almost 3 FEET of DNA in each and every cell in our bodies

Slide 7

With so much DNA in a cell, how is it organized or packaged? How is the expression of the DNA controlled?

Slide 8

1. Nucleosomes 2. Chromatin Fibers 3. Looped Domains 4. Chromosomes Focus on #1 & #4

Slide 9

Slide 10

"Beads on a String DNA wound on a protein core Packaging for DNA Controls transcription

Slide 11

Two molecules of four types of Histone proteins H1- 5th type of Histone protein attaches the DNA to the outside of the core

Slide 12

Large units of DNA/chromatin/proteins Appear only during cell division (after Interphase) Similar to "Chapters" in the Book of Life

Slide 13

1. Heterochromatin - highly condensed chromatin; areas that are not transcribed 2. Euchromatin - less condensed chromatin; areas of active transcription

Slide 14

1. Repetitive Sequences 2. Satellite DNA 3. Interspersed Repetitive DNA 4. Multigene Families

Slide 15

Give regions of the DNA different densities Linked to some genetic disorders. Ex. - Fragile X Syndrome Huntingtons disease

Slide 16

A collection of identical or very similar genes From a common ancestral gene. May be clustered or dispersed in the genome

Slide 17

Identical genes for the same protein Ex: Ribosomal Protein and rRNA Result - Many copies of ribosomes possible Most common gene in DNA

Slide 18

Related clusters of genes that are nearly identical in their base sequences. Ex: Globin Genes

Slide 19

Gene with sequences very similar to real genes, but lack promoter sites Are not transcribed into proteins Possible proof of transpositions?

Slide 20

Changes in the ways a gene can be expressed Seen only in somatic cells Have major effects on gene expression within particular cells and tissues

Slide 21

1. Gene Amplification 2. Selective Gene Loss 3. Genomic Rearrangements

Slide 22

The selective replication of certain genes Ex: rRNA genes in eggs Result - many copies of rRNA for making ribosomes

Slide 23

Loss of genes or chromosomes in some tissues during development Result - DNA (genes) lost and not expressed

Slide 24

Shuffling of DNA areas (not from meiosis) Ex: Transposons retrotransposons antibody genes Examples of Transposons: flower petals

Slide 25

Complicated Process Many levels of control are possible Hint - students should understand several mechanisms of control (see slides to follow)

Slide 26

1. Nucleus - those inside the nuclear membrane 2. Cytoplasm - those that occur in the cytoplasm

Slide 27

Slide 28

1. Extra-Cellular Signals (Chapter 11 Cell communication) 2. Chromatin Modifications 3. Transcriptional Control 4. Posttranscriptional Control

Slide 29

DNA Methylation Histone Acetylation Gene rearrangements Gene amplification

Slide 30

Addition of methyl groups (-CH 3 ) to DNA bases Result - long-term shut-down of DNA transcription Ex: Barr bodies

Slide 31

Attachment of acetyl groups (-COCH 3 ) to AAs in histones Result - DNA held less tightly to the nucleosomes, more accessible for transcription

Slide 32

Ex: Enhancers Areas of DNA that increase transcription. Ex: DNA-Binding Domains Proteins that bind to DNA and regulate transcription Ex: regulatory RNA. Small RNA molecules that are not translated Usually interact with DNA Result - genes are more (or less) available for transcription.

Slide 33

1. RNA Processing Ex - introns and exons 2. RNA Transport moving the mRNA into the cytoplasm 3. RNA Degradation breaking down old mRNA

Slide 34

1. Translation 2. Polypeptide Changes

Slide 35

Regulated by the availability of initiation factors Availability of tRNAs, AAs and other protein synthesis factors (Review Chapter 17)

Slide 36

Changes to the protein structure after translation Ex: Cleavage Modifications Activation Transport Degradation

Slide 37

Cancer - loss of the genetic control of cell division Balance between growth-stimulating pathway (accelerator) and growth- inhibiting pathway (brakes)

Slide 38

Slide 39

Normal genes for cell growth and cell division factors Genetic changes may turn them into oncogenes (cancer genes) Ex: Gene Amplification, Translocations, Transpositions, Point Mutations

Slide 40

Genes that inhibit cell division Ex - p53, p21

Slide 41

RAS - a G protein When mutated, causes an increase in cell division by over-stimulating protein kinases Several mutations known

Slide 42

p53 - involved with several DNA repair genes and checking genes. When damaged (e.g. cigarette smoke), cant inhibit cell division or cause damaged cells to apoptose.

Slide 43

Agents that cause cancer Ex: radiation, chemicals Most work by altering the DNA, or interfering with control or repair mechanisms See Chapter 17 for more on this!

Slide 44

Cancer is the result of several control mechanisms breaking down Ex: Colorectal Cancer requires 4 to 5 mutations before cancer starts

Slide 45

Colorectal Cancer

Slide 46

Recognize the operon model for gene regulation in prokaryotes. Identify different mechanisms of eukaryotic gene expression control. Recognize the roles of RNA in controlling gene expression. Recognize examples of differential gene expression in multicellular organisms. Recognize that cancer is caused by changes in gene regulation.