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Differences between Mitosis and Meiosis

Differences between Mitosis and Meiosis

In this post I have listed out main differences between mitosis and meiosis. This use to be one of the topics which was confusing to me at several points, so I made a table where I put all main differences between these two process. I hope this will help you guys too 🙂

Let’s begin with the definitions. Mitosis and meiosis are two main methods of cell divisions.

Mitosis – is a process of asexual reproduction where a cell divides in two identical daughter cells (diploid) with an equal number of chromosomes. Whereas in case of

Meiosis – the number of chromosomes are reduced by half following the separation of homologous chromosomes which results in production of four haploid daughter cells.

Differences Mitosis Meiosis
Type of Reproduction Asexual Sexual
Takes Place in / Function / Creates Somatic cells Germ cells
DNA Replication Once Once
Cell Division Once Twice
Chromosome Behavior / Pairing of Homologous Chromosomes Chromosomes behave independently of each other The homologous chromosomes forms pairs and remains adjacent to each other
Synapsis – Crossing Over and Exchange of Segments of Chromatid Crossing over and exchange does not take place Crossing over and exchange takes place
Type and Number of Chromosomes in Parent Cells Diploid (2n) – 46 chromosomes Diploid (2n) – 46 chromosomes
Type and Number of Chromosomes in Daughter Cells Diploid (2n) – 46 chromosomes Haploid (n) – 23 chromosomes
Number of Daughter Cells 2 Diploid cells 4 Haploid cells

For more explanation on this topic, watch this video 🙂

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Holoblastic Cleavage vs Meroblastic Cleavage -What is the Difference?

Holoblastic Cleavage vs Meroblastic Cleavage -What is the Difference?

When we are studying embryology, it becomes confusing sometimes if we don’t clearly remember what holoblastic and meroblastic means! So in this post we will see holoblastic and meroblastic cleavage and different type of eggs which come under these two categories. And at the end as always I will give you my trick which helps me remember this concept in super easy way. So let us begin 🙂

We know that when sperm fertilizes egg, the resultant zygote undergoes series of mitotic divisions. This division or cleavage results in 2 cells followed by 4 cells, 8 cells and so on and this embryonic cleavage can be either holoblastic or meroblastic which is specific for different species.

Holoblastic cleavage – is a complete cleavage meaning it completely penetrates the egg.

Meroblastic cleavage – is incomplete or partial cleavage meaning it does not penetrate the egg completely.

Now one question comes in mind is, why some egg follows holoblastic and some follows meroblastic cleavage? The answer is yolk content of the egg. Because yolk is bulky, it is difficult for the cleavage to take place. So eggs which contain high amount of yolk follows meroblastic cleavage (incomplete) and those which contain very low amount of yolk follow holoblastic cleavage (complete).

Based on yolk distribution in eggs, they are divided into 5 different categories. They are as follows 🙂

Holoblastic cleavage : (eggs contains low amount of yolk)

    1. Alecithal – yolk content is almost negligible or very very low.
    2. Isolechithal – yolk content is very less and it is evenly distributed. (remember Iso = even)
    3. Mesolecithal – yolk content is moderate and it is unevenly distributed. (remember M = Moderate)

Meroblastic cleavage : (eggs contain high amount of yolk)

  1. Telolecithal – high amount of yolk present in the vegetal pole of the egg. (vegetal pole is a pole where the yolk content is concentrated)
  2. Centrolecithal – high amount of yolk present in the center of the egg. (remember Centro = center)

This classification is easy to understand as we know that eggs containing high yolk will follow meroblastic cleavage and egg containing low amount of egg follows holoblastic cleavage but it becomes really confusing to remember which types comes under what. So it is time to share my trick now.

I correlate holoblastic with the word whole, it rhymes too kind of. Holo – whole, isn’t it! Try and say it out loud. So for me holo is whole meaning holoblastic is whole or complete cleavage and the remaining type is mero that would be incomplete cleavage. Now look at the classification. If you take first letters of names of eggs under holoblastic cleavage it becomes AIM and when we have aim to achieve something we put our COMPLETE effort isn’t it? So AIM is for complete or holoblastic cleavage. AIM stands for Alecithal, Isolechithal and Mesolechithal egg. The remaining two types are TC meaning Telolecithal and Centrolecithal and they follow meroblastic cleavage. This is how I remember it 🙂

I hope this was helpful 🙂

For more explanation on this topic, watch this video.