العذري التكاثر

الرحيم الرحمن الله بسم Parthenogenesis

العذري العذري التكاثر ParthenogenesisParthenogenesisالتكاثر

Definition:Definition: العذري التكاثر العذري تعريف التكاثر تعريف

Is the ability of oocytes to be produced embryos and individuals

without any fertilization, or without participation of sperm. Parthenogenesis is divided into two typesParthenogenesis is divided into two types::-

الطبيعِي�- أأ العذري الطبيعِي�- التكاثر العذري A-Natural A-Naturalالتكاثر

ParthenogenesisParthenogenesis

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>

آلخر- 1 وقت من يحدث عذري آلخر- تكاثر وقت من يحدث عذري تكاثر

11--SporadicSporadic

This type occurs with irregular shape in terms of

timing, may depend on season and availability of

environmental conditions, it was noted this type of

parthenogenesis in virgin grade squamous wings as in the

worm bed Ghaz الغز and individuals (Bambyx mori) دودة

resulting from this type are females.

I- Natural Parthenogenesis in invertebrateI- Natural Parthenogenesis in invertebrate

parthenogenesis occurs in: -

دوري- 33 عذري دوري- تكاثر عذري --33تكاثر

CyclicCyclic

This type occurs with a regular shape, after every normal

sexual reproduction occurs parthenogenesis and the example of

this is aphid from Aphidiae species ( فصيلة من المن حشرة

. أفيدي(

وثابت- 22 مستمر عذري وثابت- تكاثر مستمر عذري --22تكاثر

ConstantConstant

This type happens regularly and is the type of individuals

resulting from this type are males as in the bees النحلand the

individual resulting has a single-group chromosome (ie, has

half the number of chromosomes = 1n).

II- Natural parthenogenesis in vertebratesII- Natural parthenogenesis in vertebrates

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 ( ( الذيل سوطية of theسحلية

genus Smida Force (Cnemidophorus uniparenes) which

reproduction by parthenogenesis only and there have not

males in these species, but females practiced the mating

behavior among themselves without fertilization.

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 high

estrogen)(Figure 58),and the eggs which reproduction by

parthenogenesis in lizards produces only females. (Why

parthenogenesis in lizards produce females?)

There is also a strain of turkey reproduction by naturally

parthenogenesis and the resulting embryos are males and the male

can reproduction and produce both male and female. (Why

parthenogenesis in birds they only produce males?)

(Why parthenogenesis in lizards produce females only?)

صورة لذكر من الديك الرومِي نتج من تكاثر عذري

طبيعِي عند تزاوجه ينتج نسبة متساوية من الذكور

واإلناث.

(Why parthenogenesis in birds they only produce males?)

_B_ Bب- التكاثر العذري اإلصطناعِيب- التكاثر العذري اإلصطناعِي

ArtificialParthenogenesisArtificialParthenogenesis

This type of parthenogenesis does not spread among the organisms

in the normal case, but we can do parthenogenesis experimentally by

stimulating the eggs to be divided 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 electrical

stimulation of the eggs (stream of weak some what) 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 the types of organisms such as echinoderms (sea

urchin البحر eggs cannot to be an embryos without ( قنفذ

fertilization under natural conditions, but when these eggs

exposed to special treatments, they begin the process of

cleavage and form embryos which is known 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.

The interpretation of artificial parthenogenesis:

األصطناعِي العذري التكاثر حدوث :تفسير

It is known that, most of the eggs in the female ovaries

are in first meiosis division(Primary oocytes ابتدائية and (بويضة

some of them complete the first meiosis before ovulation and

others complete the first meiosis during ovulation to produce a

Secondary oocytes الثانوية .and the first polar body البويضة

Then, the oocytes complete the meiosis division in

most organisms within the oviduct to produce a mature

egg الناضجة القطبي and second polar body البويضة والجسم

either during the fertilize oocytes with sperm, which , الثاني

urges them to complete the meiosis division, as well as a

result of contact of sperm with a membrane the oocyte they

are form a fertilization membrane to prevent the entry of

more than sperm to the oocyte and then urges them to enter at

the stage of cleavage after the merger of male and female

nucleus.

During the ion exchange across the membrane between

the egg cytoplasm and ocean around, the egg come out the

contents of the vesicles known as cortical granules reaction

القشرية احلويصالت to be form a clear layer or gels( (تفاعل

around them to prevent the fertilized by more than sperm.

But prior to the merger between the male and female pro-

nucleus, the genetic material will be duplicated and all

chromatides turned to chromosomes, then male and female

nucleus merging to form nucleus of zygote, which is the first

nucleus of the first cell of the embryo where cleavage phase

begins in the normal matting.

Factors that control the parthenogensis processFactors that control the parthenogensis process

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 in the natural matting.

2 - Provide a second number of the chromosome set any binary

number of chromosomes (2n)

3- The central body and strings of the spindle division and

cleavage.

For inducing the artificial parthenogenesis, it can be explained by

overcome the above factors process through experiments conducted on

living organisms and that have not been the Artificial parthenogenesis.

I:The mechanical or chemical activation of oocytesI:The mechanical or chemical activation of oocytes : أوال : أوال

الكيميائِي أو الميكانيكِي والتنشيط الكيميائِي التنبيه أو الميكانيكِي والتنشيط التنبيه

:: للبويضاتللبويضات

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

division.

The mating behavior that occurs among female lizards wip

tail with parthenogenesis, this breeding behavior, urges on

the process of ovulation is also a mechanical stimulus to

activate the eggs.

It has been observed experimentally that the pricked

of unfertilized amphibians eggs with a sterilized needle,

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 granulosa reaction in the

oocytes.

Also found that when put female 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 fluids for a

short time, it can not be activated soon and it seems to rotate

shape and the form of 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.

Also found that when put female 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 fluids for a

short time, it can not be activated soon and it seems to rotate

shape and the form of 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.

(: التكWWاثر العWWذري اإلصWWطناعِي فِي بيض قنفWWذ 60شكل )

البحر بواسطة التنبيبه الكيميائِي

عن7د تع7ريض بيض قنف7ذ البح7ر غ7ير المخص7ب لمحل7ول ملحي منخفض

لم7دة قص7ي7رة ف7إ7ن ال7ب7يض تخ7تفي في7ه الثل7م7ة ويص7ب7ح كام7ل

اإلس7ت7داره7 7مم7ا ي7د7ل على 7ا7ن7ه 7كأن7ه7 بي7ض 7مخص7ب 7ثم يتفلج

عذريا.

(: التكWاثر العWذري اإلصWطناعِي فِي بيض قنفWذ البحWر 61شكل )

بواسطة التنبه الكيميائِي

عن77د تع77ريض بيض قنف77ذ غ77ير المخص77ب لمحل77ول ملحي منخفض لم77دة

ط7و7يل77ة 7ف77إن7 ا7ل77بيض ي77دخ7ل م7رحل77ة الت7ف7لج تص77بح 7فيه77ا ع77د7ة

أن7وي7ه) 7ث7الث7 أو اثن7ت7ان( م7ن الجس7م ا7لقط7بي 7األول7 أو7 الث7اني7 أو

ن7واة7 واح7د ه7ي ن7واة7 ا7لب7ويض7ة ا7لنا7ض7جة 7الناتج7ة7 م7ن االنقس7ام

االخ7تز7الي ا7لث7اني. وال7ب7يض 7المتف7ل7ج 7ال7ذي ي7ح7ت7وي 7على7 ن7و7اتين

فق77ط7 ه77و ال77ذي7 ي7نم77و7 بش77ك7ل س77لي7م7 وال7ب7قي77ة7 تنتج7 أجن77ة7 غ77ير

سليمة.

2: The nucleus of polar body to obtained the double number of 2: The nucleus of polar body to obtained the double number of

chromosomes (2n)chromosomes (2n) ددWWول على العWWبِي للحصWWم القطWWواة الجسWWدد نWWول على العWWبِي للحصWWم القطWWواة الجسWWن

الثنائِي للكروموسوماتالثنائِي للكروموسومات

It is known that eggs contain 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 (2n). 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.

This explains to us, that embryos resulting from eggs

parthenogenesis in lizards are always female, because eggs

contain sexual chromosome X only. When the egg is meiosis

divided and then merge the egg with the polar body, back to

form female (XX).

As well as, the parthenogenesis in birds 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 polar body.

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.