ميحرلا

نمحرلا الله مسب

يرذعلا رثاكتلا Parthenogenesis

Parthenogenesis يرذعلا رثاكتلا

Definition

Is the ability of oocytes to be produced embryos and individuals without any fertilization, or without participation of sperm or male. Parthenogenesis is divided into two types: -

Natural Parthenogenesis ِيعيبطلا يرذعلا رثاكتلا 1

Parthenogenesis is happens in certain species of living organisms and reproduction by sexual and natural parthenogenesis, especially in some types of invertebrates such as some worms, molluscans, freshwater crustaceans (Daphnia) and insects such as bees, ants and wasps

يعيبط يرذع رثاكتت تاذ يتلا تانئاكلا ضعب Some animals that produced parthenogenesis

يعانطصلإا حيقلتلاو يرذعلا رثاكتلا

يرذع رثاكت اهيف ثدحي يتلا ةيحلا تانئاكلا عاونا ضعب روص Some animals that have parthenogenesis

يعانطصلإا حيقلتلاو يرذعلا رثاكتلا

1- Natural Parthenogenesis in invertebrate يرذعلا رثاكتلا تايراقفلاا يف يعيبطلا

Invertebrate parthenogenesis occurs in 3 ways : -

Sporadic رخلآ تقو نم ثدحي يرذع رثاكت 1

This type occurs with irregular shape in terms of timing, may depend on season and availability of environmental conditions, this type of parthenogenesis was noted in virgin grade squamous wings as in the worm bed زقلا ةدود Ghaz (Bambyx mori) and individuals resulting from this type are females.

Constant تباثو رمتسم يرذع رثاكت

2

This type happens regularly and is the type of individuals resulting from this type are males as in the bees لحنلاand the individual resulting has half the number of chromosomes 1n).

Cyclic يرود يرذع رثاكت 3

This type occurs with a regular shape, after every normal sexual reproduction occurs parthenogenesis and the example of this is aphid from Aphidiae species .

Cyclic Parthenogenesis يرود يرذع رثاكت

 يعانطصلإا حيقلتلاو يرذعلا رثاكتلا

2- Natural parthenogenesis in vertebrates تايراقفلا يف يعيبطلا يرذعلا رثاكتلا

Occurs in some vertebrate species, as in some fish, amphibians and lizards, which overcome the process of doubling the genetic material or chromosomes in different ways, in lizards there are approximately 15-type, parthenogenesis occur in them as in the lizard reclamation or like orchid flagellar tail of the genus ليذلا ةيطوس ةيلحس سنجلا ةيداحا (

Cnemidophorus uniparenes

) which reproduction by parthenogenesis only and there have no males in these species, but females practiced the mating behavior among themselves without fertilization.

Natural parthenogensis Cnemidophorus

( ليذلا ةيطوس ةيلحس يف يرذعلا رثاكتلا ةقيرط

uniparenes)

In mating season, females with low concentration of estrogen after ovulation play the role of the male and jump on the female that in the process of ovulation, and so the cycle continues between two females one play the role of the male (with low estrogen ) and the other play the role of the female (with estrogen high) (Figure 58) , and the eggs which produc by parthenogenesis in lizards produces only females.

There is also a strain of turkey birds يمورلا كيدلا نم ةللاس reproduction by naturally parthenogenesis and the resulting embryos are males and the male can reproduction and produce both male and female.

دنع يعيبط يرذع رثاكت نم جتن يمورلا كيدلا رك ذ نم ةللاسل ةروص .

ثانلإاو روكذلا نم ةيواستم ةبسن جتني هنإف ركذلا اذه هجوازت

Artificial Parthenogenesis

يعانطصلإا يرذعلا رثاكتلا 2

This type of parthenogenesis does not spread among the organisms in the normal case, but scientist can do parthenogenesis experimentally by stimulating the ova to inter cell divisions and form embryos without the contribution of sperm to produce full configuration members .

* Methods of artificial parthenogenesis

Researchers in the field of experimental embryology such as (Whillim Ruox, Epele, Hertwing, and Loeb) try to produce embryos in organisms, that originally there is no parthenogenesis breeding, by means of mechanically as puncture of eggs of frogs by needle or by low weak electrical stimulation of the eggs or by placing eggs in a solution containing some chemical components that are active ion exchange membrane on both sides of the egg (such as potassium, sodium, calcium chloride) or weak organic acids (such as lactic acid and fat solvents as ether, acetone, and alcohol in low concentration).

Artificial parthenogenesis

echinoderms (sea urchin) In the types of organisms such as echinoderms (sea urchin) eggs cannot to be an embryos without fertilization under natural conditions, but when these eggs exposed to special treatments, they begin the process of cleavage and form embryos which is known artificial parthenogenesis. To make the parthenogenesis, put the eggs of sea urchin in a low salt solution for a short period leads to occurs of a cleavage process in the egg and produce embryos.

Factors that control the parthenogensis process يف مكحتت يتلا لماوعلا يرذعلا رثاكتلا

To induce the parthenogenesis process, main three factors must be overcome, which occurs during normal sexual reproduction between sperm and egg are 1- The mechanical stimulation of the oocyte egg that result from contact of the sperm with the egg.

2 - Provide a second number of the chromosome set any binary number of chromosomes (2 n) 3- The central body and strings of the spindle division and cleavage

The interpretation of artificial parthenogenesis ريسفت يرذعلا رثاكتلا ثودح ةقيرط

It is known that, most of the eggs in the female ovaries are in first meiosis division and some of them complete the first meiosis before ovulation to produce a secondary (Secondary oocytes and the first polar body). Then in the oviduct they complete 2 nd mioses division to produce the mature ova and 2 nd polar body.

The second polar body some time did not get out of the ova or reinter the ova and work instead of the sperm nucleolus

1-:The mechanical or chemical activation of oocytes

The treatment with chemicals or acupuncture with needle minutes or even electrical shock to the oocyte is a catalyst for the oocyte membrane to complete the meiosis II cell division.

The mating behavior that occurs among female lizards flagellar tail with parthenogenesis, this breeding behavior, urges on the process of ovulation is also a mechanical stimulus to activate the eggs.

يعانطصلإا حيقلتلاو يرذعلا رثاكتلا

It has been observed experimentally that the pricked of unfertilized amphibians eggs with a sterilized and minute eggs, activates and begins to cleavage. This mechanical stimulate works to flow of sodium ions into the oocyte and release of calcium ions to initiate the cortical granule reaction in the oocytes.

Also found that when put the sea urchin eggs containing a large germinal disc and the animal pole appearing a notch or a clear reduction (Figure 60). When treatment of these eggs and place it in the low concentration for a short time, it can not be activated soon and it seems to rotate shape and the egg fertilization membrane is formed, as a result of the characteristic low osmosis between the solution concentration and the egg cytoplasm (high concentration somewhat). This is a stimuli to the process of ionic chemical exchange between the cytoplasm of the sea urchin egg and the solution.

ةط ساوب رحبلا ذفنق ةضيوب يف يعانطصلإا يرذعلا رثاكتلا : ) 60 ( لكش يئايميكلا هبنتلا

ةدمل ض فخنم يحلم لولحمل بصخملا ريغ رحبلا ذفنق ضيب ضيرعت دنع هنا ىلع لدي ام م هرادتسلإا لماك حبصيو ةملثلا هيف يفتخت ضيبلا نإف ةريصق .

بصخم ضيب هنأك

2 : The nucleus of polar body to obtained the second number of chromosomes

It is known that eggs contain the half the number of chromosomes (1 n). So how can the eggs with a haploid set (1 n) of chromosomes become a diploid chromosome sets (2 n).

The nucleus of the polar body is alternative of the male nucleus.

When meiosis occurs, the second polar body separated from the egg and then come back and merge with the nucleus of the egg nucleus to complete the binary number of the chromosomes (2 n).

) ةقرطملا ( شرقلا كمس يف يرذعلا رثاكتلا Parthenogenesis in hammerhead shark

ةضيو بلا طشني انايحا ) ةقرطملا ( شرقلا كمسل يونملا ناويحلا .

ةضيوبلا لخاد ىلا هتاون لخدت لا نكل

يعانطصلإا حيقلتلاو يرذعلا رثاكتلا

Why parthenogenesis in Lizard produce only female and birds produce male only

This explains to us, that embryos resulting from eggs parthenogenesis in lizards are always female, because eggs contain sexual chromosome is X only. When the egg is meiosis divided and then merge the egg with the 2 nd polar body, back to form the embryo it will be female (XX).

As well as, the parthenogenesis in chicken eggs turkey produces males only and birds differ from mammals, the sexual chromosome structure of male is (ZZ) and female is (ZW), When meiosis division is occurs the one chromosome going to the egg and other to 2 nd polar body Z.

If the secondary egg take the chromosome Z and complete the second meiosis division to produce the mature egg and second polar body and did not separate or back to merge with the nucleus of second polar body to produce (ZZ) or WW. WW doesn't complete the growth because chromosome W like chromosome Y not contains the essential genes for growth or development so (WW) embryo will die or not produced so only (ZZ) embryo will produced male.

Parthenogenesis from the 2

nd

polar body

يعانطصلإا حيقلتلاو يرذعلا رثاكتلا

هبنتل ا ةطساوب رحبلا ذفنق ضيب يف يعانطصلإا يرذعلا رثاكتلا : ) 61 ( لكش يئايميكلا

ةدمل ضفخنم يحلم لولحمل بصخملا ريغ ذفنق ضيب ضيرعت دنع ) ناتنثا وأ ث لاث ( هيونأ ةدع اهيف حبصت جلفتلا ةلحرم لخدي ضيبلا نإف ةليوط ة جضانلا ةضيوبلا ةاون يه دحاو ةاون وأ يناثلا وأ لولأا يبطقلا مسجلا نم نيتاون ىلع ي وتحي يذلا جلفتملا ضيبلاو .

يناثلا يلازتخلاا ماسقنلاا نم ةجتانلا .

ةميلس ريغ ةنجأ جتنت ةيقبلاو ميلس لكشب ومني يذلا وه طقف

 Why Jeuses cant be produced from parthenogenesis?

 دق نو كي لا ملاسلا ةيلع ىسيع نوكي لا اذامل ؟يرذع رثاكت نم جتن Parthenogenesis is the production of individual without participation of sperm or male and Because human ova is (XX) and oocytes and polar bodies are (X) and if they produce by parthenogenesis they will produce only females (XX).

 Way mammals cant produce parthenogentically?

تاييدثلا رثاكتت لا اذامل ؟ايرذع It was done by experimentally in



mice and it reach the somite only and died so in mammals the paternal gens are important during embryo development

يعانطصلإا حيقلتلاو يرذعلا رثاكتلا