Meiotic cell division

12TH PHYSICS

Miotics cell division
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This division is also known as reduction division but why this name this is because in this kind of cell division the normal chromosome number of the mother cell is reduced to half and daughter cells the normal chromosome number in human being is 4623 pairs but as a result of meiosis in ovary and testis this number is house 223 and daughter cells called sperms or the egg
Where does it occur
Another productive cells example in the testis of male and in the ovary of female animals and in plants in the Pollen mother cell of the anthers male organs and in the megaspore mother cells of the ovary female organ of the flowers
Why does it occur
Enemy of the chromosome number is reduced to half so that when doubled at fertilization zygote formation during the reproduction it once again becomes restored to the deployed state
The number of chromosomes remains constant in a species generation after generation cells divide mitotically in the organisms that reproduce vegetatively asexually there is no change in the number of chromosomes but sexually reproducing organisms form government such as sperms in male and over in females the male and female gametes fuse to form the zygote formation which develops into a new individual
FB comments were produced by mitosis the offspring developing from Jagat then would have Double the number of chromosomes in the next generation every living organism has a definite number of chromosome in its body cells example onion cell 16 potato 4864 main 46 airport to keep the chromosome number constant the reproductive cells of the parents ovary and testis in animals and Pollen mother cells in anthers and megaspore mother cells in the walls inside the ovary in plants through meiosis how does meiosis occur
Meiosis is corrected by two successive divisions of the nucleus first and meiosis II
And cytoplasm whereas the chromosomes divide only once the phases of meiotic division are given in the flowchart drawn here the interfaces with proceeds the onset of meiosis is similar to the entire page which proceeds my tortoise at STP is the DNA molecule of each chromosome duplicates to give rise to to DNA molecules and hence to chromatids are found in one chromosome attached to a single centromere meiosis first and meiosis II are continuous and have been divided into substances only only for convenience to study the process of nuclear division
Meiosis first like mitosis meiosis first also consists of four states proposed first metaphase first and first and first
Please first the prophec first of meiosis first is much longer as compared to the process of Mitosis it is further subdivided into following five substages
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The chromosomes become distant and appear as long and threats bearing fan beats due to condensation calling of DNA at specific points called chromo years is chromosome consists of two chromatids held Together by a centromere but these are not easily visible nuclear membrane and nucleus are distant
Z y g o t e n e
Chromosomes continue calling and become shorter and thicker similar or homeo logos chromosome start appearing from one and this pairing is known as synopsis is fear of human chromosome is called a bivalent nuclear membrane and nucleolus are distant
P a c h y t e n e
The chromosomes become shorter and thicker due to further calling each pairing unit called a bivalent Soch 4 chromatids hence bivalent are also known as tetravalent crossing over occurs at the end of packet in IE break and exchange of parts jeans occurs between non sister chromatids chromatids of a hollow sphere the point of intersection and reasoning appears X shape and is known as Chasma plural kya aaj Mehta or the point of crossing over
D i p l o t e n e
Chromosomes continue calling for other and becomes Alter The centromeres of chromosomes start preparing each other the two non sister chromatids of a hollow sphere of chromosomes remain attached at one or two points the kya aaj beta
Nucleolus and nuclear membrane become indistinct it is at the that exchange of segments of non sister chromatids jeans between homeo logos chromosomes has taken place the process of gene exchange is known as genetic recombination
T i k i n e s i s
The Bible hands become the shortest and thickest due to maximum coiling the centromeres and non home August parts of human chromosomes of a bivalent move apart due to repulsion from each other consequently dawayi balance check via Warriors configuration such as OLX for 8:00 depending upon the number of cal metre per violent nuclear membrane and nucleolus disappear
Spindle formation is completed
M e t a p h a s e first
The Bible and arrange themselves at the equatorial plate the human chromosome are arranged in such a way that all maternal for all paternal chromosomes do not get attached to same pole in other words some maternal and some paternal chromosomes are joined to each Pole the spindle fibres are attached at the centromere of the chromosomes one centromere of a bivalent is joined to one pole and second centromere is joined to the opposite pole by the separate spindle fibres
A n a p h a s e first
The spindle fibres shorten the centromeres of homeo logos chromosomes are pulled along by spindle fibres towards the opposite poles No division of centromere does half of the number chromosomes each with 2 chromatids of the parent cell go to one pole and the remaining how to the opposite pole each set of chromosomes that moves to one pole consists of a mixture of paternal and maternal chromosome parts new combination this is the basic reason for mixing of maternal and paternal genes in the products of meiosis
T e l o p h a s e the separated chromosomes and Koel in the newly formed daughter nuclei the daughter nuclei have half the number of centromeres as compared to that in the parent nucleus but since each centromere Hetu chromatid amount of DNA at the to poles at first ACM IE to UN declared as in the parent nucleus where in the chromosomes located as page the amount of DNA in the dividing cell up to another page first was 4n
The daughter cells now have half the amount of DNA as compared to that at another page first that is 2n the nucleolus repairs and nuclear membrane forms
The daughter nuclei enter into the second meiotic division

Second meiotic division has the same four stages
Proper second metre per second and second 30 second
Professor II
The chromosomes shorten and chromatids become distant the two chromatids of each chromosome are attached to the single centromere formation of spindle starts nucleolus and nuclear membrane begin to disappear
Beta Phase II
The chromosomes arrange themselves along the equator formation of spindle apparatus is completed the centromere of each chromosome is attached by to spindle fibres to the opposite poles
Anaphase II
The centromere in each chromosome divides so that each chromatid has its own centromere and each chromatid is now a complete chromosome the chromatids get their respective centromere and become daughter chromosomes and begin to move towards the opposite poles due to contraction of spindle fibres
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Reaching the poles the chromosomes organise themselves into hapla daughter nuclei the nucleolus and the nuclear membrane reappear each of Kapoor daughter nuclei has half the number of chromosomes as well as half the amount of DNA as compared to the parent nucleus
Cytokines
Desh Mein Aakar into success stages once after meiosis first and then after meiosis II aur in some instant in occurs only after meiosis II 10 after cell division for haploid cells are formed
Significance of meiosis
It helps to maintain constant number of chromosomes in different generations of a species undergoing sexual reproduction occurs during gamete formation gametogenesis and reduce is the number of chromosomes from 12 to N in the gamets these haploid gametes fuse to form diploid zygote during fertilization The diploid zygote develops into a normal diploid individual
Meiosis established new combination of characters due to mixing of paternal and maternal chromosomes and crossing over during prophase first as a result the progeny inherits the traits of both the mother cell and father in new generation

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