Announcements
1. Genetics-related course offerings for spring 2003:
1. - BIO 324 Cell biology, 3 credits; 3 hours in lecture
2. - BIO 325 Biotechnology, 3 credits; 5 hours in lab
3. -BIO 397 Seminar in Human gene therapy, 1 credit
4. -BIO 403 Undergraduate Research, 3-4 credits; needs
to be arranged one semester in advance with faculty
5. -BIO 597Q Confocal microscopy, 4 credits
6. -BIO 597Y Techniques in molecular biology, 3 credits; 3
hours in lecture - no lab.
7. -BIO 620G Conservation Genetics, 3 credits; lecture
and lab
8. -BIO 629B Eukaryotic Molecular Genetics seminar, 1
credit
2. Ch 10: problems 1,4,13, 15 - not to turn in
Restriction Digest Lab: Use This Gel!
1 2 3 4 5
Molecular weight
markers in bp
3 real bands
Supercoiled form runs
faster, nicked form runs
slower than linearized
plasmid.
2 real bands
Bright band is cut;
faint band is uncut
Start measuring
from here.
Lanes
1 - Markers
2 - Uncut plasmid
3 - EcoRI cut
4 - DraI cut
5 - EcoRI + DraI
Review of Last Lecture
I. Sry and sex determination
II. Dosage compensation - different in humans and flies
III. Nondisjunction
•Monosomy
•Trisomy
Outline of Lecture 18
I.
Polyploidy
II.
Variation in structure/arrangement of chromosomes
- deletion
- duplication
- inversion
- translocation
III. DNA structure and analysis
I. Polyploidy
Additional sets identical to
parents.
Hybridization of closely
related species; often
sterile.
How does polyploidy arise naturally?
- DNA is duplicated in S phase but cell doesn’t go into
M phase
- Generation of Tetraploids Using Colchicine, a
Microtubule Inhibitor
Triploids can be created by inhibition of polar body
formation during oogenesis, followed by fertilization.
How is polyploidy relevant to our daily lives?
Polyploids are generally bigger than diploids;
therefore, in horticulture and agriculture they are useful.
Examples: -Bananas and tiger lilly - 3n
-coffee, peanuts, McIntosh apples - 4n
-strawberry - 8n
Somatic Cell
Hybridization
in Plants creates
Allopolyploid
Hybrids
American Cotton is natural 13 + 13
hybrid
II. Types of Chromosomal Rearrangements,
Caused by Breakage and Rejoining
Deletions
1. Chromsome breaks
2. Part is lost - a deletion
Synapsis with a chromosome
with a large intercalary
deletion - loop formation.
Duplications
Cytology showed that
bar is not due to a
gene mutation.
1. Gene redundancy
2. Phenotypic variation
3. Source of genetic
variation during
evolution
Unequal
crossing
over
Ohno’s hypothesis on the role
of gene duplication in evolution
Question: How do “new” genes arise?
Duplications might allow for major mutation in the extra
copy of the gene. Over time, mutations could result in a
new function for the duplicated gene - essentially a new
gene.
Example: myoglobin and hemoglobin
Inversions
Inversions don’t add or delete genetic info, but can have
effects on gamete formation.
Translocations
Robertsonian translocation: most common type in humans
One example:
SRY in an XX “male”
Inheritance of 14/21 Translocation
In Families with Down Syndrome
(Down)
Familial Down Syndrome Patient
with 14/21 Translocation
21
21
14/21 14
Learning check
What types of chromosome mutations are required to change
this chromosome into each of the following?
ABCDEFG
1. A B A B  C D E F G
a. inversion of A B
b. deletion of A B
c. duplication of A B
O
2. A B  E D C F G
a. translocation of C D E
b. inversion of C D E
O
c. deletion of C D E
Learning check #2
A species has 2n = 16 chromosomes. How many
chromosomes will be found per cell in each of the
following mutants in this species?
1. Monosomic
15
2. Autotriploid
24
3. Trisomic
17
4. Autotetraploid
32
III. DNA Structure and analysis
What is the genetic material?
Chromosomes contain protein and DNA - which is it?
What must genetic material do?
1. Replication
2. Storage of information
3. Expression of information
4. Variation by mutation - evolution
The Flow of Genetic Information
(The Central Dogma)
Trait
Is the Genetic Material Protein or DNA?
• Many favored proteins until the mid-1940’s.
• DNA is simple chemically; how could it then
hold complex genetic information?
• Proteins are much more complicated
chemically; perhaps they might hold genetic
information.
Evidence for DNA as Hereditary Molecule
• Transformation studies
– Griffith (1927)
– Avery, MacLeod and McCarty (1944)
• Hershey-Chase experiment (1952)
• Chargaff’s Rules
• Molecular Studies
Griffith’s Transformation Expt.
Bacteria Used
Living smooth
(virulent)
Living rough
(avirulent)
Killed smooth
Living rough +
killed smooth
Conclusion:
Killed smooth
converted
living rough to
virulent cells - a
Transforming
Principle (some
smooth
component) is
responsible.
Avery, MacLeod, and McCarty Expt:
DNA is the “Transforming Principle”
Hershey-Chase Experiment
• Radioactively labeled DNA and protein:
– 32P atom is in phosphate molecules in DNA
and RNA, only low levels in protein
(phosphorylated proteins).
– 35S atom is in sulfur containing-amino acids
(cysteine and methionine), not in DNA,
RNA.
Phage Made Radioactive
Non-radioactive medium
+ bacteria
Phage Infect Cells
32P
Phage
35S
Phage
RNA is the Hereditary Material in RNA
Viruses, e.g. TMV
Tobacco Mosaic Virus
Reconstitution of Hybrid TMV
(Fraenkel-Conrat & Singer)
Strain 1
Strain 2
Hybrid most like TMV, not HR,
therefore RNA is genetic mat’l
Bases and Sugars
pyrimidines
purines
Ribose
sugars
Bases and Sugars in DNA and RNA
• In DNA: deoxyribose + A, T, G or C
– dA
deoxyadenosine
– dT
deoxythymidine
– dG
deoxyguanosine
– dC
deoxycytidine
• In RNA: ribose + A, U, G, or C
–A
adenosine
–U
uridine
–G
guanosine
–C
cytidine
Nucleoside = Base + Sugar
Nucleotide = Nucleoside + Phosphate
U
dAMP
dNDP’s and dNTP’s:
Note Errors in the Text
deoxy
deoxy
deoxy
dNDP (dTDP)
deoxy
dNTP (dATP)
3’ to 5’ Phosphodiester Bonds Make the
Sugar-Phosphate Backbone
New Monomers
Add Here
Strand has 5’-PO4
end and 3’-OH end
Chargaff’s Rules
• 1949-1953, quantified amounts of each base in DNA
from different species.
• In every species, amount of A = Amount of T, and
Amount of G = Amount of C
• If that’s true, then A + G = C + T
• The % GC and % AT varied from species to species,
but always adds up to 100%.