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Cell Structure and Function: Comparison of Mitosis and Meiosis
Comparison of Mitosis and Meiosis
Mitosis | Meiosis |
---|---|
Cell divides only once | Two cell divisions; first and second meiotic division |
Takes place in somatic cells | Takes place in germ cells |
Occurs in both sexually as well as asexually reproducing organisms | Occurs only in sexually reproducing organisms |
Interphase occurs prior to each division | Interphase proceeds only in meiosis-I. it does not occur prior to meiosis-II |
DNA replication takes place during interphase I | DNA replication takes place during interphase β I but not interphase β II |
Duration of prophase is short (few hours) | Prophase comparatively longer (takes many days) |
Prophase simple | Prophase having five sub-stages; leptotene, zygotene, pachytene, diplotene and diakinesis |
The cell divides only once, and the chromosomes also divide only once | There are two cell divisions, but the chromosomes divide only once |
Synapsis does not occur | Synapsis of homologous chromosomes takes place during prophase |
No exchange of segments during prophase between two chromatids of chromosomes | Exchange of segments during crossing over between non-sister chromatids of two homologous chromosomes |
Each chromosome consists of two chromatids united by a centromere | Each bivalent has four chromatids and two centromeres |
The arms of the prophase chromatids are close to one another | The arms of the chromatids are separated widely in prophase β II |
Chromosomes are duplicated at the beginning of prophase | In prophase-I, chromosomes appear single although DNA, replication has taken place in interphase-I |
No bouquet stage is recorded | Chromosomes of animals and some plants show convergence towards one side during early prophase β I. it is known as bouquet stage |
Pairing of chromosomes does not occur in mitosis | Pairing or synapsis of chromosomes takes place during zygotene of prophase-I and continues up to metaphase-I |
A synaptonemal complex is absent | Synapsed homologous chromosome develop a synaptonemal complex |
Chiasmata are absent | Chiasmata or visible connections between homologous chromosomes are observed during diplotene, diakinesis (prophase-I) and metaphase-I |
In metaphase all the centromeres line up in the same plane | In metaphase I, the centromeres are lined up in two planes which are parallel to one another |
The metaphase plate is made up of duplicated chromosome | The metaphase plate is made up of paired chromosome |
The genetic constitution of the daughter cells is identical to that of the parent cells | The genetic constitution of the daughter cells differs from that of the parent cell. The chromosome of daughter cells usually contains a mixture of maternal and paternal genes |
Centromere division takes place during anaphase | No centromere divisions during Anaphase-I, centromeres divide only during Anaphase-II |
Anaphase chromosomes are single stranded | Chromosomes are double stranded in anaphase-I, but single stranded in anaphase-II |
Spindle fibers disappear completely in telophase | Spindle fibers do not disappear completely during telophase I |
Reappearance of nucleoli at telophase | Nucleoli do not appear in telophase I |
The chromosome number does not change at the end of mitosis | There is reduction in the chromosome number from diploid to haploid |
Cytokinesis follows every mitosis. It produces two new cells | Cytokinesis often does not occur after the first or reduction division. It is often simultaneous after second division to result in four new cells |
Mitosis is of shorter duration | Meiosis is of longer duration |
It is the basis of growth and repair | It is basis of maintaining chromosome number in sexual reproduction, as well as for providing variation in the progeny |
The chromosome number remains constant at the end of mitosis | The chromosome number is reduced from the diploid to the haploid |
Take part in healing and repair | Take part in the formation of mesopores or gametes and maintenance of chromosome number of the race |