Ames test
Strains inactive for
BER and prone for entry if molecules
TA100- sensitive for reversion by base pair substitution
TA 1535/8 frameshift

םיימיכ םירמוח
Chemical Agents
הנירק
Radiation
םידיינ
DNA
םיטנמלא
Mobile Genetic Elements

Ds (Dissociation)
Ac (Activator)

Insertion elements : insertion elements as mutagens gal -
, due to insertion OR “disruption”
REVERTANT: gal + revertant, due to excision of IS1

Simple transposon
(Ampicillin resistance)

Composite transposon
IS10
(tetracycline resistance)
IS10

העונתל םישרדנה םינובלחל קר םידדוקמ
IS
םיפסונ םינובלחל םג םידדוקמ
Tn

Conservative
Replicative

Animation 13_Replicative transposition

Inexact excission of IS1 can also create gal -

(Ampicillin resistance)
-There are several different types of transposable elements including insertion elements (S1, IS2 .. ) and transposons (Tn1 Tn2…)
-Many transposable elements transfer a resistance for antibiotic
-Most of the transposable elements have inverted repeats (IR) at the end which can be observed under the microscope
-Transposable elements are found on chromosome and plasmids
-After insertion into new site the elements generates a short repeats -
- Replecative vs. conservative -

• Transposons are much more common in eukaryotes.
• Some eukaryote transposable elements transpose as in prokaryote but most use similar mechanism as the RNA viruses.

LTR- long terminal repeat

םיימיכ םירמוח
Chemical Agents
הנירק
לוגסארטלוא
תנניימ
Radiation
Ultraviolet (UV)
Ionizing
םידיינ
DNA
םיטנמלא
Mobile Genetic Elements

Rearrangements

Rearrangements

Lyse Cell and its Nucleus

Karyotype- The entire chromosomes complement of an individual
Organism or cell, as seen during mitotic metaphase

Banding

SKY-Spectral karyotype

Chromocenter

A
B
C
A
B
D
E
F
E
F

Since b + and c + are “missing”, the phenotype of b and c are
“ pseudo-dominant
” or “ display pseudodominance
”:
The genes
‘across from’ the deletion “display pseudodominance”.

Inversions:
Animation 17.1a

Paracentric inversion does not span the centromere
•
Pericentric inversion does includes the centromere
•

paracentric inversion

pericentric inversion

x cM
x cM y cM
No offspring are ‘counted’ when a crossover occurs in interval y - they all die map units look like x y cM
SO – with a heterozygote for an inversion: The apparent genetic distance between genes outside the inversion seems to be reduced by y

Rearrangements

Duplications

Rearrangements

Human hemoglobin gene family:
The result of a series of gene duplications, followed by gene divergence.

Thalassemia
Thalassemia

Philadelphia chromosome or Philadelphia translocation is a specific chromosomal abnormality that is associated with chronic myelogenous leukemia (CML). It is due translocation designated as t(9;22)(q34;q11),
The fused bcr-abl protein interacts with the interleukin 3beta(c) receptor subunit.
The bcr-abl transcript is constitutively active, i.e. it does not require activation by other cellular messaging proteins. In turn, bcr-abl activates a number of cell cyclecontrolling proteins and enzymes, speeding up cell division. Moreover, it inhibits
DNA repair, causing and potentially causing the feared blast crisis in CML.

Trinucleotide repeats

Slippage during replication

Rearrangements

Reciprocal translocation chromosomes during meiosis:
Animation 17.2b

יוחיאו הריבש ידי לע ירטנצהטמל ירטנצורקאמ רבעמ
תימצע הירפה רחאל םיחמצב
הריבשה תודוקנ תא םיגציימ םיציחה
.
םימוזומורכב

Animation 17.2c
Second genetic consequence of translocations:
Pseudo-linkage

Lyse Cell and its Nucleus


הדרפה יא non-
.
מורכ disjunction
– junction
הדרפה יא

Trisomy of 13 or 18 show severe physical and mental abnormalities
Between few weeks and 130 days
Patau
Edwards
Down

*Polyploids-individual with more than two • chromosomes sets. i.e. Triploids-3n,tetraploid-
4n,pentaploid-5n,hexa….
*Monoploid- one chromosome set (not a haploid) •
*Autopolyploid (chromosomes within species) vs. allopolyploids (chromosomes from closely related species)
•
*Aneuploidy- chromosomes number is abnormal, i.e. trisomic; 2n+1, monososmic; 2n-1 and nullsomic; 2n-2.
•
In haploid n+1 is disomic

An example:
In males
X
Y
X
Y
X+Y
X+Y
Y
Y
X+X

An example:
In females
X
1
X
2
X
1
X
2
X
1
+ X
2
X
1
+ X
2
X
2
X
2
X
1
+ X
1

XXY - Kleinfeldter

XO - Turner

Animation 17.2c
Second genetic consequence of translocations:
Pseudo-linkage

X:A=1
X:A=0.5
Splicing of dsx
Male specific genes

O/o O-Orange o-Black. The white phenotype is due to other gene

Sex-linked anhidrotic ectodermal dysplasia
(absence of sweat glands in blue areas)

XXX, XXY, XXYY

*Polyploids-individual with more than two
• chromosomes sets. i.e. Triploids-3n,tetraploid-
4n,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

Diploid

Tetraploid
Polyploid

Octoploid

Generation of monoploid
Cold treatment
Embrioyoid-a small dividing mass of monoploid cells

Breeder – search for special phenotype of a/a b/b
A/a B/b recombination a b
Cold treatment monoploid colchicine
Diploid

Usually aneuploids are not viable or
• severely affected due to changes in gene balance.
In a euploid the ration between genes is 1:1 whereas in aneuploid this balance is variable

Autopolyploids the case of triploid in meiosis
Three homologous chromosomes
3:0 2:1
As more chromosome we have the less chance to get viable gamete

Polyploid with odd number of chromosome set are sterile or infertile
Since their gametes and offspring are aneuploid

Case for alloploids

ןונצ
בורכ
Karpechenko’s experiment

Non functional gamete

Distribution of haploid chrmosome number in dicotyledonous
The distribution above 12 show mainly even number suggesting doubling of chromosome sets.

6n=42

Nullisomics of modern (hexaploid) wheat

Wild type hypomorph
R
R hypermorph amorph
NULL
R ~
R ~
R
R neomorph
R ~
R ~

Standard Dominant – Recessive
Haploinsufficiency

DS-dissociation at the site of the break
Ac-Activator