Download Gene Expression, Inheritance Patterns, and DNA Technology

This Powerpoint contains information for chapters 11,
12, and 13.
Gene Expression Role
 Activation of gene =
formation of protein
 When transcription
occurs
 Mechanisms ensure that
each protein is
produced only when
needed
 2 steps = transcription
and translation
Gene Expression in Prokaryotes
 Francois Jacob and Jacques Monod
 Discovered how genes control metabolism of sugar
lactose E. Coli
 See Concept Map
Gene Expression in Eukaryotes
 Vastly different from prokaryotes
 Larger genomes
 DNA located in several individual chromosomes
instead of single circular one
 Most are multicellular made of specialized cells
 Expression is far more complex
 No operons found in eukaryotes
Three regulatory elements:
 Structural genes: ____________________
 Promoter: __________________________
 Operator: __________________________
 All three of the above terms form the
_______________________________
 What is the lac operon?
Let’s talk about E. coli
 Lactose…found in cows milk…disaccharide (glucose +
galactose)
 Let’s say you drink a glass of milk:
 Lactose entering your body stimulates E. coli to produce
3 enzymes


Control the metabolism of lactose
Adjacent on chromosome
 Production is controlled by 3 regulatory elements
 Repressor
attaches to
operator
If lactose is absent…
 Repressor protein attaches to operator
 Inhibits a specific gene from being expressed
 Prohibits RNA polymerase from binding to structural
genes = no transcription
Jobs on structural genes
 Introns – sections that do not code for a.a.
 Exons – when expressed, translated into proteins
 Unsure of benefits of intron-exon pattern
 May provide options for producing different proteins
 Could facilitate the exchange of exons among
homologous chromosomes during crossing over in
meiosis = new combination of genes

Pattern could serve as an additional source of the genetic
diversity that is essential for evolution
Control after transcription
 Gene expression can be controlled by modifying RNA
after transcription
 Pre-mRNA – lg. molecule; from transcription of introns
and exons
 Enzyme comes in and splits the pre-mRNA at each end
of an intron and then splices the exons together,
forming mRNA
 mRNA leaves nucleus and enters the cytoplasm
 mRNA begins the manufacturing of proteins on the
ribosomes
Cell Differentiation
 Development of cells having specialized functions
 Organs and tissues develop to produce a characteristic
form = morphogenesis
 Homeotic genes impact this during morphogenesis
 Homeobox = specific DNA sequence within a homeotic
gene that regulates the pattern of development
Homeotic Mutation
Homeotic genes are
regulatory genes that
determine where certain
anatomical structures (such
as appendages) will develop
in an organism during
morphogenesis
Nature of Cancer
 Tumor – uncontrolled, abnormal cell division
 Benign – remain within a mass; generally pose no threat
unless they hinder normal, vital organ functions
 Malignant – invade and destroy healthy cells
 Metastasis – spread of cancer cells beyond original site
Kinds of cancer
 Carcinomas – grow in skin and tissues (lung and
breast)
 Sarcomas – grow in bone and muscle tissues
 Lymphomas – solid tumors that grow in the tissues
that form blood cells – may cause leukemia
(uncontrolled production of wbc)
Cancer and the cell cycle
 Normal cell division – divide when needed and
when conditions are right; governed by genes that
code for growth factors
 Adequate nutrition
 Attachment to other cells, membrane, or fibers between
cells
 Cancer cell division – continue to divide in dense
environments
 Ignores cell message to stop division
 Continues to divide after no longer attached to other
cells (enables cancer to spread)
Lymphoma
Solid tumors that
grow in the tissues
that form blood
cells
Sarcoma
Grow in bone and
muscle tissue
Carcinoma
Grow in the skin and
the tissues that line
the organs of the
body
Types of
skin cancer
What to look for
Causes of cancer
 Mutations that alter the expression of genes coding
for growth factor proteins
 Can be spontaneous
 Mostly caused by carcinogens/mutagens (tobacco,
asbestos, ionizing radiation)
 Depends on factors
 Maybe genetic predisposition (mutations in gametes can
be passed to offspring)
 Exposure time to carcinogens
 Amount of carcinogen in exposures
 More than one mutation is usually needed to produce
cancer
Oncogenes
 Begin as proto-oncogenes – normal genes; control cell
growth and differentiation
 Normally code for proteins
 Regulate cell cycle (cell growth, division, ability to
adhere to other cells)
 Mutation in proto-oncogene
 Produce more protein or protein active in triggering cell
division
 Increases rate of cell cycle = cancer occurs
Tumor-suppressor genes
 Code for proteins that prevent cancer
 Mutations = proteins for which they code are either
expressed defectively or not at all - causes
predisposition to cancer
Viruses and Cancer
 Many viral genes are oncogenes
 Viruses can stimulate cancer in host cells by causing
mutations in proto-oncogenes or tumor-suppressor
genes
 Viruses may activate the cell’s own oncogenes
 Found to cause various types of leukemia
Review
 Know all vocabulary (would you expect anything less?)
you know, morphogenesis, homeoboxes, introns,
exons, etc.
 Know the pictures depicting gene expression in
prokaryotes and eukaryotes and what is happening (be
able to identify what is happening and where; steps)
 make sure you understand the lac operon!
 steps leading to formation of protein in eukaryotic cells
 Know difference between oncogene and tumor-
suppressor gene
 Know how Drosophila is used as an example with
regards to mutations.
 Know how genes can be expressed – the process
 Know types of cancer and what happens for a cell to
become cancerous
Inheritance Patterns and Human Genetics
Sex Determination
 Thomas Hunt Morgan
 Studied Drosophila
 4 Pairs of homologous chromosomes
 Noticed one pair was different between males and
females


X – appeared same in male and females
Y – shorter, hook shaped
 Gametes from meiosis II have either an X or a Y
(depending on sex of parent)
Sex Determination (cont.)
 Morgan believed the size of the X allowed it to carry
more genes
 X = X-linked genes
 Y = Y-linked genes
 Genes on sex chromosomes = sex linkage
 Morgan’s fruit fly experiments confirmed the existence
of X-linked traits
Morgan’s findings on eye color
 White-eyed male x red-eyed female = (followed
Mendel’s predictions)
 F1 generation all had red eyes
 Crossed F1 generation = F2 generation exhibited 3 red-
eyed flies to 1 white-eyed fly (all white-eyed were male!)
 Hypothesized that the gene for eye color is carried on
the X chromosome
 See Page 222 – Cross XRXR x XrY = F1 Generation
 F2 Generation – Cross XRXr x XRY
Linkage groups




Linked genes tend to be inherited together
Typically a 3:1 ratio
If on a different chromosome, they are assorted differently
Key: Grey (G) is dominant to black (g); Long (L) is
dominant to short (l)
 Morgan crossed: GGLL x ggll
 F1 = GgLl; crossed two F1 generations =
 F2 = Morgan thought if alleles were on different chromosomes,
should assort indep.




Phenotypic ratio should be 9:3:3:1
If on same chromosome, 3 gray, long-winged: 1 black, short-winged
Result closely approximated the 3:1 ratio
Hypothesized that genes are linked
What about …
 Gray, short-winged and black, long-winged appearing?
 If on same chromosome, must be some kind of
rearrangement
 Possibly couldn’t be mutations = Occur in one individual
out of tens of thousands
 Rearrangement occurred during crossing-over

Rearrangement of alleles = crossing over enables them to
change locations yielding new gene combinations (no new
genes; not deleted)
Chromosome Mapping
 Alfred H Sturtevant
 Morgan’s student
 Used crossing-over data to construct a chromosome map
of Drosophila
 Know what a chromosome map is, you won’t have to
calculate map units, etc.
Mutations
 Chg in DNA of organism
 Entire chromosome or single DNA nucleotide
 Germ Cell = Gametes; don’t affect organism but
can be passed
 Somatic = Body cells; can affect organism; not
passed to offspring
 Lethal = death, often before birth
 Beneficial? = better chance of reproducing and have
evolutionary advantage
 Variation upon which natural selection acts
Chromosome Mutations
 Deletion= loss of a piece of chromosome
 Inversion= chromosomal segment breaks off then
reattaches in reverse orientation to same chromosome
 Translocation= a chromosome piece breaks off and
reattaches to another, nonhomologous chromosome
 Nondisjunction= failure of a chromosome to separate
from its homologue during meiosis
 Ex.
Gene Mutations
 Point = substitution, addition, or removal of a single
nucleotide
 Substitutions = sickle cell anemia is a result of a point
mutation that substitutes adenine for thymine in a
single DNA codon
 Frame-shift =
 What happens? See Figure 12-8
12.2
 Pedigrees = family record that shows how a trait is
inherited over several generations
Ewww
Traits controlled by single allele
 Traits controlled by a single allele
 Huntingtons disease (HD)…single, dominant allele
located on an autosome
 Genetic Marker (short section of DNA known to have
close association with a particular gene located nearby)
 Cystic Fibrosis (CF) and sickle cell anemia are single,
recessive allele: only fully expressed when the individual
has two copies of the recessive allele (homozygous rec)
Traits controlled by multiple alleles
 Controlled by 3+ alleles of the same gene that code for
a single trait
 ABO blood groups
 IA, IB, and i
 IA, IB = codominant (both expressed when together);
both dominant to the i allele
Genotype
Blood type
IAIA
A
IAi
A
IBIB
B
IBi
B
IAIB
AB
ii
O
Polygenic Traits
 Trait that is controlled by two or more genes
 Skin color (3-6 genes); eye color; human height (also
influenced by environmental and nutritional factors)
 Show many degrees of variation
X-Linked Traits
 Colorblindness – recessive X-linked disorder – cannot
distinguish between certain colors
 Hemophilia – recessive X-linked disorder - impairs
the ability of the blood to clot following a cut, bruise,
or other injury
 Duchenne Muscular Dystrophy – weakens and
progressively destroys muscle tissue
 NOT ALL or even most X-linked traits are diseases
(code for proteins that perform many normally needed
functions in the body)
Sex-influenced Traits
 Presence of male or female
hormones influence the expression
of certain human traits:
 Males and females have different
phenotypes even when they have
same genotype

Pattern baldness (dominant in males;
recessive in females)
 BB = both will eventually lose hair;
allele B’ codes for normal, nonbald
phenotype = BB’ female does not lose
hair; BB’ male does (due to
testosterone levels
 Most are located on autosomes
Disorders due to nondisjunction
 Familiarize yourself with Table 12-3 on page 230
 Can cause gametes to lack a chromosome or to have an extra
chromosome
 Zygotes (sperm + egg) can have either 45 or 47 (often lethal)
 45 = monosomy (one copy of chromosome) (Turner Syndrome)
 47 = trisomy (three copies)
Trisomy
 Trisomy 21 = extra copy of chromosome 21 = Down
Syndrome
 Mild to severe mental retardation
 Characteristic facial features
 Muscle weakness
 Heart defects
 Short stature
Down
Syndrome
Nondisjunction and sex chromosomes
 Males with extra copy of X = Klinefelter’s syndrome (XXY)
 Some feminine characteristics
 Some are mentally retarded
 Some are infertile
 Individuals that inherit a single Y do not survive = X
contains information essential for development
 Individuals that have a single X instead of a pair = Turner’s
syndrome
 Female appearance
 Do not mature sexually
 infertile
Klinefelter’s Syndrome
Turner’s Syndrome
Early Testing
 Be able to define these terms and for what they are used
 Amniocentesis
 Chorionic villi sampling
Awkward “Relatives”
More….
More….
Same
DNA Technology
DNA Technology
 Used to cure diseases, treat genetic disorders, improve
food crops, & many other things to improve our lives
 DO NOW: Trace the path of the restriction enzyme
using 5 post-its…be able to explain what is happening.
Use your text, pages 239-240 to better gain an
understanding for your explanation.
How does it all happen?
 DNA is a long chain of nucleotides
 Restriction enzymes cut DNA into more manageable
segments
 Sticky ends are created

Readily bind to complementary chains of DNA
 Can be used to isolate a particular gene
 A cloning vector can transfer the gene to an organism
Transplanting Genes
 What would be the need to transplant genes? Talk
with your table
 Transplant to bacteria to produce quantity faster
 Ex. Insulin (page 241)

Mass quantity can be made for those who do not produce
enough insulin
 Isolate gene using restriction enzyme
Techniques
 DNA fingerprint
 RFLP = restriction fragment length polymorphism

DNA extraction from blood or other tissue; cut into fragments
using restriction enzymes
 Gel electrophoresis = separates nucleic acids/proteins
according to size and charge


Place samples in wells in gel
Use electric current to cause fragments to migrate at different
rates based on size (separated by size)
 PCR = polymerase chain reaction = used if only a very
tiny amount of DNA is available…allows to make copies
of DNA