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

םינגטומ Mutagens

םיימיכ םירמוח Chemical Agents

הנירק Radiation

םידיינ DNA םיטנמלא Mobile Genetic Elements

Barbara McClintock

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

םינגטומ Mutagens

םיימיכ םירמוח Chemical Agents

הנירק

לוגסארטלוא תנניימ

Radiation

Ultraviolet (UV) Ionizing םידיינ DNA םיטנמלא Mobile Genetic Elements

Rearrangements

Rearrangements

Human

Karyotype

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

“ 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 •

םיכופיה Inversions

paracentric inversion

The trouble with paracentric inversion: Animation 17.1b

pericentric inversion

םיכופיה

x cM

Inversions

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.

Thalassemias

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 cycle controlling 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

Human

Karyotype – Trisomy 21

Lyse Cell and its Nucleus 

הדרפה יא non .

מורכ – junction הדרפה יא

Non-disjunction in Meiosis I: Animation 18.1a

Non-disjunction in Meiosis II: Animation 18.1b

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

םיחנומ

*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

Monosomy: Karyotype minus 1 chromosome homolog םוזומורכ לש דחא ) גולומוה ( קתוע רסח Nullisomy: Karyotype minus both chromosome’s homologs םירסח דחא םוזומורכ לש ) םיגולומוה ( םיקתועה ינש

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

Y?

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

םיחנומ

*Polyploids-individual with more than two 4n,pentaploid-5n,hexa….

•

chromosomes sets. i.e. Triploids-3n,tetraploid *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

2n 4n

Aneuploid and gene balance

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

Allele names according to phenotype

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