Download Mendelian Genetics Mutation Topics: Source of genetic variation:

Mendelian Genetics
Mutation
Topics:
Source of genetic variation:
√√
-Transmission of DNA during cell division
√√
Mitosis and Meiosis
- Segregation
√√
- Sex linkage
√√
- Inheritance and probability
√√
√√
√√
√√
√√
- Mendelian genetics in humans
- Independent Assortment
- Linkage
- Gene mapping
Gene Mutation
√√ - somatic, germinal
√√
√√
√√
Chromosome mutations (Ch. 11)
√√ - structure
- number
- Tetrad Analysis (mapping in fungi)
- Extensions to Mendelian Genetics
- Gene mutation
- Chromosome mutation
- 3 point test cross
1
Euploidy
Chromosome Mutation
(2. changes in number)
Euploidy:
2
variation in complete sets of
chromosomes
Aneuploidy: variation in parts of chromosome
sets
1x
2x
3x
4x
5x
6x
3
monoploid (1 set) = n
diploid
(2 sets) = 2n
triploid
tetraploid
pentaploid
polyploid (> 2 sets)
hexaploid
n = # chromosomes in the
gametes
4
Polyploids
Polyploids
Larger
Autopolyploids: within one species
than Diploids
Allopolyploids: from different, closely
related species
5
6
1
Polyploids
Formation of Triploids
Triploids: = 3n
- problems with pairing during
meiosis
- unbalanced gametes
- usually sterile
Applications: seedless fruits, sterile fish
aquaculture
n
= 3n
n
n
Polar
bodies
n
n
= 3n
2n
n
7
Triploids (3x)
8
Fig. 11-5
Why can’t a triploid produce viable
gametes ?
9
Triploids (3x)
x=1
10
Triploids
Gametes
x=2
Gametes
viable
or
Nonviable
11
12
2
Triploids
Autotetraploid
Doubling of chromosomes: 2x----> 4x
Even number of chromosomes: normal meiosis
2<---->2 segregation------> functional gametes
Probability (2x or x gamete) =
1
2
( )
if x = 10
x -1
Prob. = 0.002 of viable gametes
13
Origin of
Wheat
Fig. 11-10
14
Allopolyploid
2n = 14, n = x = 7
Polyploidy
hybrid
Plants:
speciation
2n = 28
Chromosome
sets:
n = 14
Animals:
A, B, D
7
14
Triploid
- rare (sex determination)
- fish (salmon)
- parthenogenetic animals
7 7 7
123
11
22 12
12
2n = 42 x = 7
n = 21
15
Chromosome Mutation
(changes in number)
Plant Polyploids
90
% Polyploids
16
80
70
Euploidy:
60
50
variation in complete sets of
chromosomes
40
30
30
40
50
60
70
80
Aneuploidy: variation in parts of chromosome
sets
90
Latitute North
17
18
3
Aneuploidy
Aneuploidy
Nullisomics (2n - 2)
19
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
20
21
22
Monosomics (2n - 1)
Trisomics (2n + 1)
Aneuploidy
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
23
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
24
4
G-bands
Downs Births per 1000
Downs Births per 1000
25
20
15
10
5
0
20
13
21
X
25
30
35
40
45
50
Maternal Age (years)
18
Y
25
26
Mutations Causing Death and
Disease in Humans
% of live births
Gene mutations:
1.2
Chromosome mutations:
0.61
27
Chromosome Mutations
(Humans)
Trisomics
XO
Triploids
Tetraploids
Others
Chromosome
abnormalities
28
Chromosome Mutations
% of spontaneous abortions
26 %
9%
9%
3%
3%
50 %
29
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)
30
5
Summary
Mutation
Detecting
Mendelian Genetics
- gene
- chromosome
(structure, number)
- cytology
genetic
analysis
- phenotype
Topics:
-Transmission of DNA during cell division
Mitosis and Meiosis
- Segregation
- Sex linkage
Quiz 3
- Inheritance and probability
- Mendelian genetics in humans
- Independent Assortment
- Linkage
Rate of mutation - low
Mutation
- source of genetic variation
- evolutionary change
- Gene mapping
- 3 point test cross
31
- Tetrad Analysis (mapping in fungi)
- Extensions to Mendelian Genetics
- Gene mutation
- Chromosome mutation
32
Chapter References
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
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