Download Genetics --- introduction

Test 2
Thursday Nov. 17
Quiz 4 answers
http://webct.mun.ca:8900/
All quizzes on WebCT for Review
Office Hours: Tuesday 10:30 – 12:00
Wed. 1:15 – 2:15
or by appointment: 737-4754, [email protected]
Mendelian Genetics
Topics:

-Transmission of DNA during cell division







Mitosis and Meiosis
- Segregation
- Sex linkage (problem: how to get a white-eyed female)
- Inheritance and probability
- Independent Assortment
- Mendelian genetics in humans
- Linkage
- Gene mapping



-Gene mapping in other organisms
(fungi, bacteria)
- Extensions to Mendelian Genetics
- Gene mutation
- Chromosome mutation
(- Quantitative and population genetics)
B2900
Mutation
Source of genetic variation:
Gene Mutation
 - somatic, germinal
Chromosome mutations (Ch. 11)
 - structure (deletion, duplication, inversion, translocation)
- number
Chromosome Mutation
(2. changes in number)
Euploidy:
variation in complete sets of
chromosomes
Aneuploidy: variation in parts of chromosome
sets
Euploidy
1x monoploid (1 set) = n
2x diploid
(2 sets) = 2n
3x triploid
4x tetraploid
5x pentaploid
polyploid (> 2 sets)
6x hexaploid
2n
4n
n = # chromosomes
in the gametes
Polyploids
Autopolyploids: within one species
Allopolyploids: from different, closely
related species
Polyploids
Larger
than Diploids
Polyploids
Triploids: = 3n
- problems with pairing during
meiosis
- unbalanced gametes
- usually sterile
Applications: seedless fruits, sterile fish
aquaculture
Formation of Triploids
n
= 3n
n
n
Polar
bodies
n
n
= 3n
2n
n
Triploids (3x)
Why can’t a triploid produce viable
gametes ?
Fig. 11-5
Triploids (3x)
x=1
Gametes
Triploids
Gametes
x=2
viable
or
Nonviable
Viable Gametes from Triploids
0.5
x-1
( )
1
2
# of chrs
2
0.4
Probability of Viable Gametes
Probability
(2x or x gamete) =
0.3
3
0.2
4
0.1
0
0
if x = 10 Prob. = 0.002
of viable gametes
5
10
15
20
Number of Chromosomes
25
30
35
Triploid Fish
Frankenfish-Biotech
3n carp
Autotetraploid
Autotetraploid
Doubling of chromosomes: 2x----> 4x
Even number of chromosomes: normal meiosis
2<---->2 segregation------> functional gametes
Polyploids
Autopolyploids: within one species
Allopolyploids: from different, closely
related species
Hybridization
Origin of
Wheat
Fig. 11-10
Allopolyploid
2n = 14, n = x = 7
hybrid
2n = 28
Chromosome
sets:
n = 14
A, B, D
7
14
Triploid
7 7 7
2n = 42
x=7
n = 21
Polyploidy
Plants: speciation (wheat)
Animals: - rare (sex determination)
- fish (salmon: tetraploid)
- parthenogenetic animals
123
11
22 12 12
Plant Polyploids
% Polyploids
90
80
70
60
50
40
30
30
40
50
60
70
Latitute North
80
90
Chromosome Mutation
(changes in number)

Euploidy:
variation in complete sets of
chromosomes
Aneuploidy: variation in parts of chromosome
sets
Aneuploidy
Nullisomics (2n - 2)
Monosomics (2n - 1)
Trisomics (2n + 1)
normal
Aneuploidy
Nullisomics (2n - 2)
- lethal in diploids
- tolerated in polyploids
Monosomics (2n - 1)
- disturbs chromosome balance
- recessive lethals hemizygous
Trisomics (2n + 1)
- sex chromosomes vs autosomes
- size of chromosome
Aneuploidy
Non-disjunction:
Meiosis I
Meiosis II
Gametes
n+1 n-1
n+1 n-1
n
n
x
n - 1 ---------> 2n - 1 monosomic
n
x
n + 1 ---------> 2n + 1 trisomic
Human Aneuploids
13
18
21
X
Y
Aneuploidy
Humans: (live births)
Monosomics - XO Turner syndrome
- no known autosomes
Trisomics XXY Klinefelter sterile male
XYY fertile male ( X or Y gametes)
XXX sometimes normal
21
Down
18
Edwards
syndromes
13
Patau
Downs Births per 1000
Downs Births per 1000
25
20
2%
15
10
5
0
20
25
30
35
40
45
Maternal Age (years)
50
0.62 %
50 %
Mutations Causing Death and
Disease in Humans
% of live births
Gene mutations:
1.2
Chromosome mutations:
0.61
Chromosome Mutations
(Humans)
Trisomics
XO
Triploids
Tetraploids
Others
Chromosome
abnormalities
% of spontaneous abortions
26 %
9%
9%
3%
3%
50 %
Chromosome Mutations
Comparison of euploidy with aneuploidy
Aneuploids more abnormal than euploids:
likely due to gene imbalance
Plants more tolerant than animals to
aneuploidy and polyploidy
(animal sex determination)
Summary
Mutation
Detecting
- gene
- chromosome
(structure, number)
- cytology
genetic
analysis
- phenotype
Rate of mutation - low
Mutation
- source of genetic variation
- evolutionary change
Chapter References
Mitosis and Meiosis
Ch. 4 p. 100 – 112 Prob: 10, 11, 12, 18, 19
Mendelian Inheritance
Ch. 5 p. 118 – 129 Prob: 1 – 3, 5, 6, 7, 8, 9
Recombination, linkage maps
Ch. 6 p. 148 – 165 Prob: 1-5, 7, 8, 10, 11, 14
Extensions to Mendelian Genetics
Ch. 14 p. 459 – 473 Prob: 2, 3, 4, 5, 6, 7
Chromosome Mutations
Ch. 11 p. 350 – 377 Prob: 1, 2
Mendelian Genetics
Topics:

-Transmission of DNA during cell division







Mitosis and Meiosis
- Segregation
- Sex linkage
- Inheritance and probability
- Independent Assortment
- Mendelian genetics in humans
- Linkage
- Gene mapping




-Gene mapping in other organisms
(fungi, bacteria)
- Extensions to Mendelian Genetics
- Gene mutation
- Chromosome mutation
Genetics
Part I
Molecular
Part II
Mendelian
Chromosome Theory of
Inheritance
- genes organized into chromosomes
- correlation: Genetics & Cytology
- theory can explain segregation and
independent assortment
Two types of nuclear division
1. Mitosis (somatic tissue)
2. Meiosis (germ tissue)
Mendelian Genetics
• Meiosis and mitosis
• Segregation and independent assortment
• Sex linkage, sex determination
• Pedigrees
• Linkage, recombination and linkage maps
Mendelian Genetics
• Gene linkage: 3 point test cross, tetrad analysis
• Extensions (dominance, multiple alleles, pleiotropy, epistasis,
penetrance and expressivity)
• Mutation: gene mutation
chromosome mutation (number
structure)
Mendelian Genetics
Applications
Genetic markers as tools:
- human diseases
- population genetics
- genetic structure (gene flow)
- systematics and phylogeny
- forensics
Mendelian Genetics
in Humans
Determining mode of inheritance
Problems:
1. long generation time
2. can not control matings
Alternative:
* information from matings that have
already occurred “Pedigree”
Human Pedigrees
Pedigree analysis:
•
•
•
trace inheritance of disease or condition
provide clues for mode of inheritance
however, some pedigrees ambiguous
Human Pedigrees
Pedigree analysis:
dominant vs recessive
autosomal vs sex linked
Linkage:
Human Genetic Diseases
Linkage:
• organization of genes and genome
• marker genes linked to:
Disease genes
Mutation
Gene Mutation
- somatic, germinal
- detecting mutations
Chromosome mutations
- structure
- number
Chromosome Mutation
(changes in number)
Euploidy:
variation in complete sets of
chromosomes
Aneuploidy: variation in parts of chromosome
sets
Careers in Genetics
cytogenetics
molecular genetics
human genetics
population genetics
quantitative genetics
developmental genetics
immunogenetics
etc. etc.
Genetics Courses
B2900
B2060
B3530
B4241
B4250
B4900
Principles of Evolution and Systematics
Principles of Cell Biology
Developmental Biology
Advanced Genetics
Evolutionary Genetics
Biotechnology
Honours Thesis Research in Genetics
Announcement
NSERC
Undergraduate Student
Research Awards (USRA) in
Universities
16 weeks $5,625
www.nserc.ca
MUN deadline Early Jan, 2006