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Cell Divison Part 3~1

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Cell Divison Part 3~1

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Cell Cycle & Cell Division - Mitosis - Part 3

Mitosis takes place in somatic cells and in germinal cells during multiplication phase. It is also known as equational division as the chromosome number is same in both the daughter cells and the parent cell.

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Cell Cycle & Cell Division - Meiosis I - Prophase I - Part - 3

In prophase I of meiosis I crossing over between non sister chromatids takes place which results in genetic recombination and variations.

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Meiosis | Cell Cycle & Cell Division (Part 3) | Class 11

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Events during Meiosis are explained in very simple student friendly language and in HINDI. The video will help a lot scoring high in Board exam and Pre Medical Tests.

Find answers to questions asked in the video:

Answer 1: Yes

Answer 2: No, mutation is the source of variation in these organisms.

Cell Cycle and Cell Division | Biology Class 11

Meiosis: It ensures production of haploid gametes in sexually reproducing organisms where fertilization leads to formation of diploid zygote (the first cell of next generation).

Key feature of meiosis:

It involves two sequential cycles of nuclear and cell division but only a single cycle of DNA replication.

It involves pairing of homologous chromosomes and recombination between them.

Four haploid daughter cells are formed at the end of meiosis II.

Meiosis I: Two homologous chromosomes of each pair separate from each other and go to separate daughter cells. This reduces the number of chromosomes from diploid (2n) to haploid (n). Therefore meiosis I is also known as reductional division.

Prophase I: It is the longest phase and is divided into 5 sub stages:

· Leptotene

· Zygotene

· Pachytene

· Diplotene

· Diakinesis

Note: A mnemonic in hindi “Lata Zara Paani De Dena”.

Leptotene:

Chromosomes gradually become visible under microscope as slender threads.

Condensation of chromatin fibres continues.

Centrioles move a part.

Spindle begins to develop.

Zygotene: Homologous chromosomes come to lie side by side in pairs, the process is called Synapsis (Figure 10). Pairing is so through that all the corresponding points (genes) lie exactly opposite to each other. A pair of homologous chromosomes lying together is known as bivalent or tetrad. A fibrillar organelle called synaptonemal complex develops between the synapsed homologous chromosomes.

Pachytene:

This stage is characterized by appearance of recombination nodules, the sites at which crossing over occurs between non sisters chromatids of homologous chromosomes.

Crossing over is the exchange of genetic material between two homologous chromosomes. It occurs by breakage and reunion of chromatid segment.

Diplotene:

Dissolution of synaptonemal complex results in separation of homologous chromosomes of bivalents, except at the sites of crossovers. The process of separation of homologous chromosomes is called disjunction.

X-shaped structures so formed are called chiasmata.

Diakinesis:

The chiasmata disappear by sliding towards the tips of chromosomes; the process is called terminalization.

Nucleolus and nuclear membrane disintegrate.

Chromosomes lie free in cytoplasm.

Metaphase I:

Homologous chromosomes lie in two parallel metaphase plates at equator.

Microtubules from the opposite poles of spindle attach to pair of homologous chromosomes.

Anaphase I: The homologous chromosomes separate, while sister chromatids remain associated at their centromeres.

Telophase I:

Nuclear membrane and nucleolus reappear.

Cytokinesis follows.

Interkinesis: A short lived interval between two meiotic divisions.

Significance of meiosis I:

Separates homologous chromosomes so that the number of chromosomes reduces to half.

Introduces variation through crossing over.

At times causes chromosomal mutations by abnormal disjunctions.

Meiosis II: It is equational division because chromosome number remains the same as produced by meiosis I. Thus, meiosis II resembles a normal mitosis.

Prophase II:

Centrioles move apart.

Spindle is laid down between centrioles.

Chromosomes become visible due to condensation.

Nucleoli disappear.

Nuclear membrane disintegrates.

Metaphase II:

Chromosomes align at equator forming single metaphase plate.

Microtubules from opposite poles of spindle get attached to kinetochores of sister chromatids.

Anaphase II:

Centromeres of each chromosomes split.

Chromatids of each chromosome start moving towards opposite poles of the cell.

Telophase II:

Chromosomes become extended.

Spindle is lost.

Nucleoli and nuclear membrane reappears.

Meiosis II is not mitosis:

1. Occurs with haploid number of chromosomes.

2. Not proceeded by interphase.

3. Two chromatids of a chromosome are not similar due to crossing over in meiosis I.

Significance of meiosis:

Maintains specific chromosome number of each species.

Crossing over and random recombination increases genetic variability in population. Variations are very important for the process of evolution.

Concept Tutorial presents ‘Meiosis’ in very simple language to help students in the best possible way.

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Cell Cycle & Cell Division - Cell Cycle - Part 3

Cell cycle includes preparatory phase and a division phase. The phases inter phase and M phase.

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Cell: Structure and Functions -

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Biology Cell Cycle & Cell Division part 3 (Binary Fission) CBSE class 11 XI

Biology Cell Cycle & Cell Division part 3 (Binary Fission) CBSE class 11 XI

Cell Cycle & Cell Division Class 11th , NEET & AIIMS | Meiosis { PART- 3} by :- Dr. S.K.Singh

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Dr.S.K SINGH (MBBS.)





Cell Cycle and Mitosis [3D Animation]

Cell Cycle and Mitosis animation
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mitosis 3d animation |Phases of mitosis|cell division

Phases of mitosis:This animation demonstrates the stages of mitosis in an animal cell.

Mitosis is the process in which a eukaryotic cell nucleus splits in two, followed by division of the parent cell into two daughter cells. The word mitosis means threads, and it refers to the threadlike appearance of chromosomes as the cell prepares to divide. Early microscopists were the first to observe these structures, and they also noted the appearance of a specialized network of microtubules during mitosis. These tubules, collectively known as the spindle, extend from structures called centrosomes — with one centrosome located at each of the opposite ends, or poles, of a cell. As mitosis progresses, the microtubules attach to the chromosomes, which have already duplicated their DNA and aligned across the center of the cell. The spindle tubules then shorten and move toward the poles of the cell. As they move, they pull the one copy of each chromosome with them to opposite poles of the cell. This process ensures that each daughter cell will contain one exact copy of the parent cell DNA.


Interphase: Cells may appear inactive during this stage, but they are quite the opposite. This is the longest period of the complete cell cycle during which DNA replicates, the centrioles divide, and proteins are actively produced. For a complete description of the events during Interphase, read about the Cell Cycle.

Prophase: During this first mitotic stage, the nucleolus fades and chromatin (replicated DNA and associated proteins) condenses into chromosomes. Each replicated chromosome comprises two chromatids, both with the same genetic information. Microtubules of the cytoskeleton, responsible for cell shape, motility and attachment to other cells during interphase, disassemble. And the building blocks of these microtubules are used to grow the mitotic spindle from the region of the centrosomes.

Prometaphase: In this stage the nuclear envelope breaks down so there is no longer a recognizable nucleus. Some mitotic spindle fibers elongate from the centrosomes and attach to kinetochores, protein bundles at the centromere region on the chromosomes where sister chromatids are joined. Other spindle fibers elongate but instead of attaching to chromosomes, overlap each other at the cell center.

Metaphase: Tension applied by the spindle fibers aligns all chromosomes in one plane at the center of the cell.

Anaphase: Spindle fibers shorten, the kinetochores separate, and the chromatids (daughter chromosomes) are pulled apart and begin moving to the cell poles.

Telophase: The daughter chromosomes arrive at the poles and the spindle fibers that have pulled them apart disappear.

Cytokinesis: The spindle fibers not attached to chromosomes begin breaking down until only that portion of overlap is left. It is in this region that a contractile ring cleaves the cell into two daughter cells. Microtubules then reorganize into a new cytoskeleton for the return to interphase.

cell division of meiosis and mitosis

meiosis cell division in plant and animal.
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cell division / part 1 prep 3

cell division

Mitosis: The Amazing Cell Process that Uses Division to Multiply! (Updated)

Updated Mitosis Video. The Amoeba Sisters walk you through the reason for mitosis with mnemonics for prophase, metaphase, anaphase, and telophase. Expand details to see table of contents.👇 Video handout here:

Table of Contents:
Why is Mitosis Important? 0:44
Why Don't You Want Cells Dividing all the Time? 2:00
Interphase (occurs before mitosis) 2:23
DNA and Chromosomes 2:55
Chromosome Replication 4:07
PMAT Mitosis Stages 5:30
Cytokinesis (actual splitting of cell) 7:30

We appreciate the feedback we get for what we need to clarify or should have added. Here is a clarification (also pinned in comments): (1) We mention mitosis as a type of cell division. To be specific, it's a division happening within the cell - in the nucleus. But we do not introduce the nucleus until later on in video. Mitosis is specifically the division happening of the nucleus whereas cytokinesis follows to do the actual splitting of the cell (mentioned at 7:30). (2) Our video is intended to focus on animal cells (as drawn) - specifically human cells - as we use human chromosome numbers. We wish we had clarified that more as we appreciate the feedback that the statements, Mitosis makes body cells. Meiosis makes gametes. has some big exceptions such as plants. (3) In metaphase, we do not draw a nucleus (6:09), because we mention it already has been disassembled. Disassembly of the nuclear membrane (envelope) occurs at the end of the previous stage. Many texts will state this is during prometaphase, a stage in between prophase and metaphase. In this short video, we do not include prometaphase. We only mention that the nucleus is no longer there by the time it's metaphase. (4) Notice our illustration in anaphase also includes a text box that says sister chromatids separate at 6:37. It's important to understand that chromosomes are moved away in anaphase, but as the text box notes, realize they are separated by the pulling apart of sister chromatids. This is especially important when comparing mitosis to meiosis I---as you can see our comparison video (which has more detail) here:

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The Amoeba Sisters videos demystify science with humor and relevance. The videos center on Pinky's certification and experience in teaching biology at the high school level. For more information about The Amoeba Sisters, visit:

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Cell Division and Reproduction Part 3

Cell division part 3

Mitosis: Splitting Up is Complicated - Crash Course Biology #12

Hank describes mitosis and cytokinesis - the series of processes our cells go through to divide into two identical copies.

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References for this video can be found in the Google document here:

Table of Contents
1. Mitosis 0:24
2. Interphase 3:27
a) Chromatin 3:37
b) Centrosomes 3:52
3) Prophase 4:14
a) Chromosomes 4:18
b) Chromatid 4:31
c) Microtubules 5:07
4) Metaphase 5:22
a) Motor Proteins 5:36
5) Biolography 6:13
6) Anaphase 9:00
7) Telophase 9:15
8) Cleavage 9:25
9) Cytokinesis 9:36

This video contains the following sounds from Freesound.org:
Swishes.wav by Pogotron
Opening Scotch Whisky.mp3 by Percy Duke

crashcourse, biology, mitosis, cell biology, cell division, cell, replication, splitting, chromosome, diploid cells, nucleus, DNA, prophase, metaphase, anaphase, telophase, interphase, chromatin, chromatid, centrosome duplication, centromere, microtubules, motor protein, walter flemming, tomomi kiyomitsu, dynein, cleavage, cytokinesis, daughter cells, science, education, college, university, learn, teach, hank green Support CrashCourse on Patreon:
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Comparing mitosis and meiosis | Cells | MCAT | Khan Academy

Comparison of the processes of mitosis and meiosis.

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CELL DIVISION / MEIOSIS (EASY WAY) / NCERT/ NEET

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CELL DIVISION / MEIOSIS (EASY WAY) / NCERT/ NEET

CELL DIVISION MITOSIS:-

CELL CYCLE:-

CELL DIVISION NUMERICALS:-

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CELL DIVISION PART 2 MITOSIS AND AMITOSIS

This video is about cell division which explains complete chapters and mcq practice in four parts part 1 introduction of cell division and interphase part 2mitosis part 3 meiosis part 4 mcq practice.

VIDEOS OF BIOLOGY SUBJECT FOR BASIC CONCEPT TO HIGHER STANDARD LEVEL FOR NEET AIIMS AND BSC MSC PHD

Part 1 How to crack NEET through our channel

Part 1 Introduction and interphase

Science | Prep.3 |Unit4 Lesson 1 |Cell division |Part 2/2|1st.Term

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Class10 | SSC | Types of Cell Division | Science 2 | Maharashtra Board | Home Revise

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Cell division is one of the very important properties of cells and living organisms. Due to this property only, a new organism is formed from existing one, a multicellular organism grows up and emaciated body can be restored.
There are two types of cell division as mitosis and meiosis. Mitosis occurs in somatic cells and stem cells of the body whereas meiosis occurs in germ cells. Before study of cell division, we should know the structural organization of cell that we have studied earlier. Each cell has a nucleus. Besides, other cell organelles are also present. Let us study the cell division with the help of this information.
Before any type of cell division, the cell doubles up its chromosome number present in its nucleus i.e. if chromosome number is 2n, it is doubled up to 4n.

Mitosis:
Somatic cells and stem cells divide by mitosis. Mitosis is completed through two main steps. Those two steps are karyokinesis (nuclear division) and cytokinesis (cytoplasmic division). Karyokinesis is completed through four steps.

A. Prophase : In prophase, condensation of basically thin thread-like chromosomes starts. Due to this, they become short and thick and they start to appear along with their pairs of sister chromatids. Centrioles duplicate and each centriole moves to opposite poles of the cells. Nuclear membrane and nucleolus start to disappear.

B. Metaphase: Nuclear membrane completely disappears in metaphase. Chromosomes complete their condensation and become clearly visible along with their sister chromatids. All chromosomes are arranged parallel to equatorial plane (central plane) of the cell. Special type of flexible protein fibers (spindle fibers) are formed between centromere of each chromosome and both centrioles.

C. Anaphase: In anaphase, centromeres split and thereby sister chromatids of each chromosome separate and they are pulled apart in opposite directions with the help of spindle fibers. Separated sister chromatids are called as daughter chromosomes. Chromosomes being pulled appear like bunch of bananas. In this way, each set of chromosomes reach at two opposite poles of the cell.

D. Telophase : The chromosomes which have reached at opposite poles of the cell now start to de-condense due to which they again become thread-like thin and invisible. Nuclear membrane is formed around each set of chromosomes reached at poles. Thus, two daughter nuclei are formed in a cell. Nucleolus also appears in each daughter nucleus. Spindle fibers completely disappear.
In this way, karyokinesis completes and cytokinesis begins.
The cytoplasm divides by cytokinesis and two new cells are formed which are called as daughter cells. In this process, a notch is formed at the equatorial plane of the cell which deepens gradually and thereby two new cells are formed. However, in case of plant cells, instead of the notch, a cell plate is formed exactly along midline of the cell and thus cytokinesis is completed.
Mitosis is essential for growth of the body. Besides, it is necessary for restoration of emaciated body, wound healing, formation of blood cells, etc.

Meiosis:
Meiosis is completed through two stages. Those two stages are meiosis-I and meiosis-II. In meiosis-I, recombination/ crossing over occur between homologous chromosomes and thereafter those homologous chromosomes (Not sister chromatids) are divided into two groups and thus two haploid cells are formed.

Meiosis-II is just like mitosis. In this stage, the two haploid daughter cells formed in meiosis-I undergo division by separation of recombined sister chromatids and four haploid daughter cells are formed. Process of gamete production and spore formation occurs by meiosis. In this type of cell division, four haploid (n) daughter cells are formed from one diploid (2n) cell. During this cell division, crossing over occurs between the homologous chromosomes and thereby genetic recombination occurs. Due to this, all the four daughter cells are genetically different from parent cell and from each other too.

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