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Aneuploidy:
changes in parts of chromosome sets
-monosomics (2n-1)
-trisomics (2n+1)
etc.
Aberrant euploidy:
abnormal # of whole chromosome sets
2
-triploidy (3n)
-tetraploidy (4n)
etc.
Chromosome Constitutions in a Normally Diploid Organism with
Three Chromosomes (Labeled A, B, and C) in the Basic Set
Number of chromosomes
Constitution
3
ABC
6
AA BB CC
9
AAA BBB CCC
12
AAAA BBBB CCCC
Designation
Name
n
Monoploid
2n
Diploid
3n
Triploid
4n
Tetraploid
5
5
5
A
BB CC
AA B
CC
AA BB C
2n − 1
Monosomic
7
7
7
AAA BB CC
AA BBB CC
AA BB CCC
2n + 1
Trisomic
3
Chromosome mutations
4
Diploid
Polyploid
Tetraploid
Octaploid
5
Grapes
2n
4n
Watermelon
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‫מונחים‬
*Polyploids-individual with more than two •
chromosomes sets. i.e. Triploids-3n,tetraploid4n,pentaploid-5n,hexa….
*Monoploid- one chromosome set (not a haploid) •
*Autopolyploid (chromosomes within species) vs. •
allopolyploids (chromosomes from closely related
species)
*Homeologous- Partially homologous (common •
ancestor)
*Aneuploidy- chromosomes number is abnormal, i.e. •
trisomic; 2n+1, monososmic; 2n-1 and nullsomic; 2n-2.
In haploid n+1 is disomic
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Generation of monoploid
Cold treatment
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Embrioyoid-a small dividing mass of monoploid cells
2n
->
1n
X
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Breeder – search for special phenotype of a/a b/b c/c d/d
recombination
A/a B/b C/d D/d
Cold treatment
abc
d
monoploid
(Diploid)
10
Generation of monoploid
Cold treatment
A/a B/b C/c D/d
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Among them:
abc
d
Embrioyoid-a small dividing mass of monoploid cells
Among them:
a 2n
b c ->
d
1n
Breeder – search for special phenotype of a/a b/b c/c d/d
recombination
A/a B/b C/d D/d
Cold treatment
abc
d
monoploid
colchicine
Diploid
12
abc
d
13
a/a b/b c/c d/d
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How does colchicine work?
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abc
d
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a/a b/b c/c d/d
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Why is a monoploid sterile?
n=2
When they enter meiosis,
Segregation leading to
normal gametes is rare
OR
OK
Not OK
n=2
2 * 1/2n are OK = 1/2
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n=10 More typical for plant
2 * 1/2n are OK = 1/516
-chance that all chromosomes go to one gamete
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Autopolyploids: the case of triploids in meiosis
Three homologous chromosomes
3:0
2:1
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As more
chromosomes we have the less chance to get viable gamete
Polyploid with odd number of chromosome set are sterile or infertile
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Since their gametes and offspring are aneuploid
Aneuploid, aberrant euploidy, and
gene balance
• Usually aneuploids are not viable or
severely affected due to changes in gene
balance.
In a euploid the ratio between genes is 1:1
**even in aberrant euploidy, -whereas in
aneuploid this balance is variable
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‫מונחים‬
*Polyploids-individual with more than two •
chromosomes sets. i.e. Triploids-3n,tetraploid4n,pentaploid-5n,hexa….
*Monoploid- one chromosome set (not a haploid) •
*Autopolyploid (chromosomes within species) vs. •
allopolyploids (chromosomes from closely related
species)
*Homeologous- Partially homologous (common •
ancestor)
*Aneuploidy- chromosomes number is abnormal, i.e. •
trisomic; 2n+1, monososmic; 2n-1 and nullsomic; 2n-2.
In haploid n+1 is disomic
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‫צנון‬
‫כרוב‬
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Karpechenko’s experiment
Non functional gamete
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Distribution of haploid chrmosome number in dicotyledonous
‫פסיגיים‬-‫דו‬
The distribution above 12
show mainly even number
suggesting doubling of
chromosome sets.
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6n=42
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Guns, Germs, and Steel. Jared Diamond
Nullisomics of modern (hexaploid) wheat
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Trisomics of Datura
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Aneuploid, aberrant euploidy, and
gene balance
• Usually aneuploids are not viable or
severely affected due to changes in gene
balance.
In a euploid the ratio between genes is 1:1
**even in aberrant euploidy, -whereas in
aneuploid this balance is variable
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So why not polyploid mammals?
Remember the issue of balance between chromosomes
For plants, tetraploidy works–TWICE as much of EVERY GENE, so ok.
In mammals, a balance has evolved for all chromosomes,
including sex chromosomes
e.g.: humans have 45 active chromosomes (and sometimes Y).
Dosage compensation, through Barr Bodies, makes sure
That only 1 X is active (even when 2, 3, 4, and more are present)
So, with higher multiples of autosomes, but active X # not budging,
balance can never be correct.
XXX, XXY, XXYY
Imprinting, a later topic,
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is also a problem.
‫תורשה חוץ גרעינית‬
‫‪36‬‬
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Molecular Biology of the Cell
Endosymbiosis
Primary
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Biology - Campbell and Reece, 8th Ed. (2008).
Figure 1
Primary and secondary endosymbiosis might explain
the extraordinary diversity of protists.
Primary endosymbiosis
Mito-ONCE >1.5 BYa, Plastids-ONCE ±1.5 BYa
--Organelles gained through endosymbiosis.
Secondary endosymbiosis
--A eukaryote, the product of an endosymbiosis, participates in another.
--Evolved multiple times.
Figure 3
Diversification of protists into 7 main groups
Archaeplastids led
to modern plants.
Unikonts led to
modern fungi and
animals.
Archaeplastida
Red algae
(Chlorophyll a
and phycobiliproteins)
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4
Green algae
(Chlorophyll a and b)
1
Modern phylogenetic
tree of protists,
plants, fungi and animals
2
3
4
5
Biology - Campbell and Reece,
8th Ed. (2008).
44
Modern phylogenetic
tree of protists,
plants, fungi and animals
Arche
a
Organelle genomes work with an
alternative genetic code!
Male parents generally
DO NOT
Contribute cytoplasm to
zygotes
SO… mitochondria and chloroplasts are
MATERNAL CONTRIBUTIONS
Ron ended
Here on Jan 12.
Male parents generally
DO NOT
Contribute cytoplasm to
zygotes
SO… mitochondria and chloroplasts are
MATERNAL CONTRIBUTIONS
Note: In human mitochondria, the mutation rate is ±10-5 (per generation per bp)
Here too: For Mitochondrial DNA, recombination is NOT AN ISSUE
Cytokinesis
(Cell Division)
-actin microfilaments
and Karyokinesis
(Nuclear division,
including mitosis)
-tubulin microtubules
:‫דוגמא‬
‫שיח נוי‬
(Variegated) Pittosporum
Maternal effect (NOT Maternal inheritance)
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Case for alloploids
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