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?
"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.