Cytology Part 2

Hi guys, you're welcome to mystudyrom my name is David.

Hope the first part helped you a lot and if you are not getting it or feel confused you can use the comment box below…thanks

Today I will continue from my last topic in Biology which is Cytology.

 In the last part I stopped at the components of the cell and their functions but today we will GI a little bit deep into the cell where we shall study the cell cycle and the cell division.

But before I move to that let me give you the similarities and differences between the plant and the animal cell.

Starting with differences

·         The plant cell has a large vacuole while the animal cell has small vacuole

·         The plant cell is rectangular in shape while the anal cell is spherical

·         The plant cell store lipid as oil while the animal cell store lipid as fat

·         The plant cell has a cellulose cell wall while the animal cell has no cellulose cell wall

·         The plant cell lacks centriole while centrioles is present in the animal cell

·         The plant cells contains chlorophyll which is the photosynthetic pigment while the animal cell lacks chlorophyll

·         The plant cell stores carbohydrates as starch while the anal cell stores carbohydrates as glycogen

  

So guys let's check the similarities between the plant cell and the animal cell

Similarities:

·         They both have nucleus

·         They both have cytoplasm

·         They both have mitochondrion

·         They both have Golgi bodies

·         They both have cell membrane

·         They both have ribosome

·         They both have endoplasmic reticulum

So guys that's it about the plant and animal cell so we are now moving in to the cell cycle.

CELL CYCLE:

The cell cycle is a series of event by which a cell duplicates its genome, synthesizes the other constituents of the cell and then eventually divides into two daughter cell.

All cells reproduce by dividing into two with each parental cell dividing into two daughter cells each time they divide and during this division DNA replication and cell growth also takes place.

Now let's move into the phases of cell cycle

The cell cycle is divided into two phases which are:

The interphase and the M phase.

The M phase is Aldo known as the mitotic phase.

Interphase:

The interphase is also called the resting stage because in the interphase the cell will be getting ready to undergo cell growth and DNA replication respectively.

The interphase consists of three phases which are :

The G1 phase

The S phase and

The G2 phase

Let me shine a little light in these three and then move on.

The G1 phase:

It is the initiation stage where the cells becomes active and then continues to grow.

The S phase:

This is also known as the synthesis phase where DNA replication takes place.

The G2 phase:

In this phase the protein synthesized cell continues to grow.

Now let's move to the second part in the cell cycle which is the M phase

M phase:

Thus is also known as the mitotic phase where the mitosis occurs and as we all know mitosis is divided into four stages which are:

Prophase

Metaphase

Anaphase and the

Telophase.

From here now i will be going into cell division

What is cell division?

Cell division is the process by which cells multiply to increase in number.

There are two types of cell division which are

The Mitotic division (mitosis) and the

Meiotic division also called meiosis.

Starting with mitosis, what is mitosis?

Mitosis is a type of cell division following the duplication of chromosome in which each daughter cell has thesame number of chromosome as the parent.

Mitosis takes place in somatic cells ( body cells that are not involved in the production of gametes).

In plants mitosis occurs at the terminal bus of the shoot while in animals mitosis occurs at all growth areas.

In mitosis the offspring are identical to the parent due to the replication of DNA.

As I've said earlier mitosis is divided into four stages which are:

Prophase

Metaphase

Anaphase and the

Telophase.

Now let's take a look what happens in all these stages listed

Prophase:

Chromosomes becomes condensed and are seen to be composed of two chromatids attached together.

Centrioles moved towards the opposite sides of the nucleus.

Metaphase:

Disintegration of the nuclear envelope occurs and the chromosome spread through the cytoplasm

Anaphase:

Each chromosome arranged at the metaphase plate is splitted and moves to the opposite sides of the pole.

Telophase:

Cytokinesis occurs (This is the splitting of the cytoplasm of the cell).

Nuclear envelope starts to reform.

Significance of mitosis:

·         It helps in growth

·         It aids reproduction in the lower organisms

·         It helps to repair worn out tissue

·         It helps ti give rise ti offsprings which are identical to the parents.

And now MEIOSIS

What is meiosis?

Meiosis is a type of cell division in which four daughter cells are produced and these daughter cells are haploid.

Meiosis takes place in reproductive gametes e.g ovules and pollen grains in flowering plants nd ovaries and testes in animals.

There are two stages in meiosis and this is because if the formation of the four daughter cells. What do I mean by the formation of four daughter cell makes meiosis has two different stages? let's check it out

STAGE 1

PROPHASE 1: prophase I is subdivided into:

Leptotene:   Chromosomes becomes visible

Zygotene:   Synapsis occurs ( this is a process whereby homologous chromosomes comes together to form bivalent

Pachytene:   Crossing over occurs between the non-sister chromatids (this is the exchange of genetic materials between two homologous chromosomes) this process occurs at the chaismata

Diplotene:   Bivalent separates from each other

Diakinesis:   Chromosomes become fully condensed to move to the next stage.

METAPHASE 1:

The bivalent align at the equatorial plate.

Anaphase 1:

The homologous chromosome separate while the sister chromatic remain associated at the centromere

Telophase 1:

Cytokinesis occurs.

At the end if this stage only two daughter cells are formed.

Now Stage II

Prophase II:

Nuclear envelope disintegrate and the  becomes visible

Metaphase II:

chromosomes align at the equator

Anaphase II:

Sister s seperate and moves towards the opposite pole of the cell

Telophase II:

Cytokinesis occurs.

The two daughter cell now forms four daughter cells.

Now I hope you guys now understand why meiosis undergo two stages……

Significance of meiosis:

·         It helps in reproduction

·         Helps in increasing genetic variability.

Question of the day

---   Why are the offspring produced in meiosis not identical to their parents?

---  what are the differences between mitosis and meiosis?

Post your answers in the comment section below and you are also free to ask questions just put your questions in the comment box.

Guys hope it helped. please comment for any question, guide or help see you all in my next post guys…

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Thanks

Holuwarseun…