Announcements

1
Announcements

• 1. Genetics-related course offerings for spring
  2003
• - BIO 324 Cell biology, 3 credits 3 hours in
  lecture
• - BIO 325 Biotechnology, 3 credits 5 hours in
  lab
• -BIO 397 Seminar in Human gene therapy, 1 credit
• -BIO 403 Undergraduate Research, 3-4 credits
  needs to be arranged one semester in advance with
  faculty
• -BIO 597Q Confocal microscopy, 4 credits
• -BIO 597Y Techniques in molecular biology, 3
  credits 3 hours in lecture - no lab.
• -BIO 620G Conservation Genetics, 3 credits
  lecture and lab
• -BIO 629B Eukaryotic Molecular Genetics seminar,
  1 credit
• 2. Ch 10 problems 1,4,13, 15 - not to turn in

2
Restriction Digest Lab Use This Gel!
1 2 3 4 5
Start measuring from here. Lanes 1 - Markers 2 -
Uncut plasmid 3 - EcoRI cut 4 - DraI cut 5 -
EcoRI DraI
Molecular weight markers in bp
3 real bands
2 real bands
Supercoiled form runs faster, nicked form
runs slower than linearized plasmid.
Bright band is cut faint band is uncut
3
Review of Last Lecture

• I. Sry and sex determination
• II. Dosage compensation - different in humans and
  flies
• III. Nondisjunction
• Monosomy
• Trisomy

4
Outline of Lecture 18

• Polyploidy
• Variation in structure/arrangement of chromosomes
• - deletion
• - duplication
• - inversion
• - translocation
• III. DNA structure and analysis

5
I. Polyploidy
Hybridization of closely related species often
sterile.
Additional sets identical to parents.
6
How does polyploidy arise naturally?- DNA is
duplicated in S phase but cell doesnt 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.
7
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

8
Somatic Cell Hybridization in Plants
createsAllopolyploidHybridsAmerican Cotton is
natural 13 13 hybrid
9
II. Types of Chromosomal Rearrangements, Caused
by Breakage and Rejoining
10
Deletions

• Chromsome breaks
• Part is lost - a deletion

Synapsis with a chromosome with a large
intercalary deletion - loop formation.
11
Duplications
Cytology showed that bar is not due to a gene
mutation.

• Gene redundancy
• Phenotypic variation
• Source of genetic variation during evolution

Unequal crossing over
12
Ohnos 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
13
Inversions
Inversions dont add or delete genetic info, but
can have effects on gamete formation.
14
Translocations
Robertsonian translocation most common type in
humans
One example SRY in an XX male
15
Inheritance of 14/21 Translocation In Families
with Down Syndrome
(Down)
16
Familial Down Syndrome Patient with 14/21
Translocation
21 21 14/21 14
17
Learning check

• What types of chromosome mutations are required
  to change this chromosome into each of the
  following?
• A B ? C D E F G
• A B A B ? C D E F G
• a. inversion of A B
• b. deletion of A B
• c. duplication of A B
• A B ? E D C F G
• a. translocation of C D E
• b. inversion of C D E
• c. deletion of C D E

O
O
18
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?
• Monosomic
• Autotriploid
• Trisomic
• Autotetraploid

15 24 17 32
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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
20
The Flow of Genetic Information (The Central
Dogma)
Trait
21
Is the Genetic Material Protein or DNA?

• Many favored proteins until the mid-1940s.
• DNA is simple chemically how could it then hold
  complex genetic information?
• Proteins are much more complicated chemically
  perhaps they might hold genetic information.

22
Evidence for DNA as Hereditary Molecule

• Transformation studies
• Griffith (1927)
• Avery, MacLeod and McCarty (1944)
• Hershey-Chase experiment (1952)
• Chargaffs Rules
• Molecular Studies

23
Griffiths 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.
24
Avery, MacLeod, and McCarty ExptDNA is the
Transforming Principle
25
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.

26
Phage Made Radioactive
Non-radioactive medium bacteria
27
Phage Infect Cells
32P Phage
35S Phage
28
RNA is the Hereditary Material in RNA Viruses,
e.g. TMV
Tobacco Mosaic Virus
29
Reconstitution of Hybrid TMV (Fraenkel-Conrat
Singer)
Strain 1
Strain 2
Hybrid most like TMV, not HR, therefore RNA is
genetic matl
30
Bases and Sugars
pyrimidines
purines
Ribose sugars
31
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

32
Nucleoside Base SugarNucleotide Nucleoside
Phosphate
U
dAMP
33
dNDPs and dNTPsNote Errors in the Text
deoxy
deoxy
deoxy
deoxy
dNTP (dATP)
dNDP (dTDP)
34
3 to 5 Phosphodiester Bonds Make the
Sugar-Phosphate Backbone
New Monomers Add Here
Strand has 5-PO4 end and 3-OH end
35
Chargaffs 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 thats true, then A G C T
• The GC and AT varied from species to species,
  but always adds up to 100.