Question

Starting with One Cell describe step by step the process of Meiosis I in males and females (they have different end results). How many viable cells are there for the male and for the female at the end of Meiosis I?

Answer 1

Meiosis I is also know as reductional divisions .

Both males and females use meiosis to produce their gametes.

In females produce egg(ova),in males produce sperm.

Meiosis I in males and females is same .

Meiosis is a slow process, because of the time that the cell spends in prophase I.

Meiosis I, also known as reduction division since it reduces the diploid number of chromosomes in each daughter cell by half.

This first step is further subdivided into four main stages i.e. prophase I, metaphase I, anaphase I,and telophase I.

Prophase I takes up the greatest amount of time (more than 90 percent of meiosis in Prophase I), especially in oogenesis(production ovum).

Because this particular step includes so many events, it is further subdivided into

• Leptotene – condensation of chromosomes and are attached to the nuclear membrane via their telomeres
• Zygotene – Synapsis begins with a synaptonemal complex forming between homologous chromosomes
• Pachytene – Crossing-over of genetic material occurs between non-sister chromatids
• Diplotene – Synapsis ends with disappearance of synaptonemal complex ;homologous pairs remain attached at chiasmata(x shaped)
• Diakinesis – The final stage of the prophase I , characterized by shortening and thickening of the paired chromosomes, formation of the spindle fibers, disappearance of the nucleolus, and degeneration of the nuclear membrane.

Metaphase I :-Spindle fibres from opposing centrosomes connect to bivalents (at centromeres) and align them along the middle of the cell

Anaphase I: -Spindle fibres contract and split the bivalent, homologous chromosomes move to opposite poles of the cell

Telophase I:-Chromosomes decondense, nuclear membrane may reform, cell divides (cytokinesis) to form two haploid daughter cells.

In the  end of meiosis I two haploid daughter cells forms .

next to meiosis II :- 4 sperm in male and one egg in female in complete meiosis.