Meiosis Stages and Characteristics

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Questions and Answers

What is the main difference between prophase-1 and prophase-2 in meiosis?

Prophase-1 is simpler, while prophase-2 is complex (correct)

Prophase-1 occurs in mitosis, while prophase-2 occurs in meiosis

Prophase-1 is complex, while prophase-2 is simpler

Prophase-1 occurs in meiosis I, while prophase-2 occurs in meiosis II

What is the correct sequence of events in meiosis?

Prophase-1 followed by interkinesis

Prophase-2 followed by interkinesis

Interkinesis followed by prophase-1

Interkinesis followed by prophase-2 (correct)

What is the correct statement about metaphase-2 in meiosis?

Spindle fibers do not attach to the kinetochore of sister chromatids

Chromosomes align at the equator, and 2 metaphasic plates are formed

Chromosomes align at the equator, and 1 metaphasic plate is formed (correct)

Chromosomes do not align at the equator

What is the correct statement about anaphase-2 in meiosis?

Both A and C Signup and view all the answers

What is the significance of meiosis in sexually reproducing organisms?

All of the above Signup and view all the answers

What is the correct statement about telophase-2 in meiosis?

Cytokinesis occurs, and the formation of two cells occurs Signup and view all the answers

What is the number of haploid cells formed at the end of meiosis?

4 Signup and view all the answers

In which phase of the cell cycle is meiosis initiated?

S phase Signup and view all the answers

What is the characteristic of prophase of meiosis 1 compared to prophase of mitosis?

It is longer and more complex Signup and view all the answers

Which stage of prophase 1 is characterized by the pairing of non-homologous chromosomes?

Zygotene Signup and view all the answers

What is the correct sequence of stages in prophase 1 of meiosis?

Leptotene, Zygotene, Pachytene, Diakinesis, Diplotene Signup and view all the answers

What is the site where crossing over occurs between sister chromatids of homologous chromosomes?

Recombination nodule Signup and view all the answers

What is the correct statement about the starting of crossing over in meiosis?

Crossing over occurs at the starting of crossing over, leaving the chromosome linked at the site of crossover. Signup and view all the answers

What happens during Diplotene stage of meiosis?

Diplotene can't suspend for months or years in oocytes of some vertebrates. Signup and view all the answers

What is the correct statement about Diakinesis stage of meiosis?

Chromosomes are fully condensed and spindle fibers are assembled to prepare homologous chromosomes for separation. Signup and view all the answers

What happens during Metaphase I of meiosis?

Sister chromatids separate and attach to centromere. Signup and view all the answers

What happens during Anaphase I of meiosis?

Homologous chromosomes separate and sister chromatids do not separate. Signup and view all the answers

What is the correct statement about Telophase I of meiosis?

Cytokinesis occurs and tetrad of cells are formed. Signup and view all the answers

What is the correct statement about the stage between two meiotic divisions?

It is called interkinesis and is long-lived. Signup and view all the answers

What is the correct statement about the outcome of crossing over in meiosis?

It leads to the recombination of genetic material. Signup and view all the answers

Study Notes

Meiosis

Four haploid cells are formed at the end of meiosis.
Meiosis is initiated after the duplication of parental chromosomes (DNA) in the S phase, where identical sister chromatids are produced.

Prophase 1

Prophase 1 of meiosis is shorter and more complex compared to prophase of mitosis.
It is divided into five stages: Leptotene, Zygotene, Pachytene, Diakinesis, and Diplotene.
In Leptotene, chromosomes gradually become visible in a light microscope, and compaction or condensation of chromosomes does not occur.
In Zygotene, pairing of homologous chromosomes occurs, facilitated by the synaptonemal complex, forming a bivalent or tetrad, which is more visible in this stage.
In Pachytene, recombination nodules are formed, where crossing over occurs between sister chromatids of homologous chromosomes.
Crossing over leads to the recombination of genetic material and occurs at the starting of crossing over, leaving the chromosomes linked at the site of crossover.

Diplotene and Diakinesis

In Diplotene, homologous chromosomes of bivalents start separating each other, even at the crossover site, and chiasmata are formed at the site of crossover.
In Diakinesis, the terminalization of chiasmata occurs, chromosomes are fully condensed, and spindle fibers are assembled to prepare the homologous chromosomes for separation.

Metaphase 1 and Anaphase 1

In Metaphase 1, bivalent chromosomes align on the equatorial plate, and microtubules from opposite poles of the spindle attach to the kinetochore of homologous chromosomes.
In Anaphase 1, homologous chromosomes separate, and sister chromatids do not separate, attaching to the centromere.

Telophase 1 and Interkinesis

In Telophase 1, the nucleolus and nuclear membrane disappear, but cytokinesis does not occur, and tetrad of cells are not formed.
Interkinesis is a short-lived stage between two meiotic divisions, and it is not followed by DNA replication and centriole duplication.

Meiosis 2

Meiosis 2 resembles mitosis and is called an equational division.
Prophase 2 starts immediately after cytokinesis, usually before chromosomes fully elongate.
In Metaphase 2, chromosomes align at the equator, and one metaphasic plate is formed.
In Anaphase 2, splitting of centromere does not occur, and elongation of microtubules attached to kinetochore occurs.
In Telophase 2, meiosis ends, and two groups of chromosomes are enclosed by nuclear membrane, followed by cytokinesis and the formation of two cells.

Significance of Meiosis

Meiosis conserves chromosome number from generation to generation in sexually reproducing organisms, even though the process paradoxically results in a reduction of chromosome number by half.
Meiosis leads to genetic variability and is essential for evolution.

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Description

This quiz assesses knowledge of the meiosis process, including the number of haploid cells formed, the initiation of meiosis, and the characteristics of prophase-1 and leptotene.