Meiosis is a type of cell division that produces gametes, such as sperm and egg cells, with half the normal number of chromosomes. It involves two rounds of cell division called Meiosis I and Meiosis II. In Meiosis I, homologous chromosome pairs separate and are distributed into two daughter cells. Meiosis II then separates the sister chromatids, resulting in four haploid daughter cells each with a single set of chromosomes. This ensures genetic diversity in the next generation.
Meiosis is the special type of cell division in which the number of chromosomes in daughter cells reduces to half, as compared to the parent cell. It takes place in diploid cells only, in animals at the time of gamete formation, while in plants when spores are produced.
It is the presentation on the MEIOSIS phase of the Cell division.
It includes all the details and definitions that are related to the topic of meiosis with the labelled diagrams.
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Meiosis is the special type of cell division in which the number of chromosomes in daughter cells reduces to half, as compared to the parent cell. It takes place in diploid cells only, in animals at the time of gamete formation, while in plants when spores are produced.
It is the presentation on the MEIOSIS phase of the Cell division.
It includes all the details and definitions that are related to the topic of meiosis with the labelled diagrams.
If you have any query or a question, you may ask in the comment box.
thanks.
– Male and female gametes fuse together during fertilization to form a zygote. The chromosome number is halved during the formation of gametes by the process of meiosis. This maintains the chromosome number generations after generations. Meiosis leads to genetic diversity which is very essential for evolution.
The slides contain all about meiosis. in this slides i collected all information about meiosis. which is useful for everyone.
so watch these slides and comment for any problems.
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– Male and female gametes fuse together during fertilization to form a zygote. The chromosome number is halved during the formation of gametes by the process of meiosis. This maintains the chromosome number generations after generations. Meiosis leads to genetic diversity which is very essential for evolution.
The slides contain all about meiosis. in this slides i collected all information about meiosis. which is useful for everyone.
so watch these slides and comment for any problems.
thanks
4. Cell division - Anatomy - BSc Nursing 1st Semester - by M. Thirumurugan.pptxthiru murugan
It is the process by which a parent cell divides into two or more daughter cells. Cell division usually occurs as part of a larger cell cycle.
It is an essential biological process in many organisms. It is the means used by multicellular organisms in order to grow, repair, and reproduce.
Types of Cell division:
Mitosis
Meiosis
Mitosis: Mitosis is a division of the nucleus to produce two new daughter cells containing chromosomes identical to the parent cell.
Phases of Mitosis:
Mitosis is a continuous process and divided into different phases based on the appearance and behavior of the chromosomes.
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis
1.Prophase:
Early prophase:
During prophase chromatin (the complex of DNA and proteins contained in the nucleus), condense and become visible in a light microscope
Nucleolus disappears & Paired centrioles move to opposite ends of the cell.
The replicated chromosomes have an X shape and are called sister chromatids. The sister chromatids are joined at a point called the centromere.
Late prophase:
Nuclear membrane disappears
a structure called the mitotic spindle begins to form at opposite ends of the cell (responsible for separating the sister chromatids into two cells)
2. Prometaphase: Prometaphase is the second stage of mitosis. In prometaphase,
Chromosomes continue to condense
Kinetochores appear at the centromeres
Mitotic spindle attach to kinetochores
Centrosomes move toward opposite poles
3. Metaphase:
Metaphase is the third step in mitosis.
Mitotic spindle is fully developed
Sister chromatids line up at the spindle equator
At the end of metaphase, the centromeres start to divide
4.Anaphase:
Anaphase begin with the separation of the centromeres
Sister chromatids together break down
Sister chromatids (now called chromosomes) are pulled toward opposite poles
The sister chromatids are drawn to opposite poles of the cell by contraction of spindle fibers
5.Telophase:
Telophase begin when the two sets of daughter chromosomes have reached the two poles of the cell.
The spindle fibers breaks down,
The nuclear membrane forms around each set of daughter chromosomes and the nucleoli reappear
The chromosomes uncoil and become less visible under the light microscope
6. Cytokinesis:
Cytokinesis is the sixth and final step of mitosis & A cleavage furrow separates the daughter cells
Cytokinesis is the process of cytoplasmic division to form two daughter cells.
Cytokinesis takes place when the Cytoplasm divides and two cells with identical genetic material are formed Daughter Cells
Meiosis:
Meiosis Takes place in the Gametes of an organism
People have a Chromosome count of 46
When an egg joins a sperm the count must stay at 46 to remain human
So, the egg can only have 23 chromosomes, and the sperm can only have 23 chromosomes
But, the integrity of the organism must be maintained.
During Meiosis diploid cells are reduced to haploid cells
Diploid (2n) to Haploid (n):
During Meiosis gamete (sex
ntry points of glucogenicamino acids after transamination
are indicated by arrows extended from circles
the key gluconeogenicenzymes are enclosed in double
bordered boxes. oated fashion. They are interdependent; each forms a strand in the web of life. Parasitology is
the science that deals with organisms living in the human body (the host) and the medical significance of
this host-parasite relationship.
ASSOCIATION BETWEEN PARASITE AND HOST
A parasite is a living organism, which takes its nourishment and other needs from ahost; the host is an
organism which supports the parasite. The hosts vary depending on whether they harbor the various
stages in parasitic development
DIFFERENT KINDS OF PARASITES
Ectoparasite – a parasitic organism that lives on the outer surface of its host, e.g. lice, ticks, mites etc.
Endoparasites parasites that live inside the body of their host, e.g. Entamoeba histolytica.
Obligate Parasite- This parasite is completely dependent on the host during a segment or all of its life
cycle, e.g. Plasmodium spp.
Facultative parasite – an organism that exhibits both parasitic and non-parasitic modes of living and
hence does not absolutely depend on the parasitic way of life but is capable of adapting to it if paced on
a host. E.g. Naegleria fowleri
Accidental parasite – when a parasite attacks an unnatural host and survives. E.g. Hymenolepis diminuta
(rat tapeworm).
Erratic parasite - is one that wanders in to an organ in which it is not usually found. E.g. Entamoeba
histolytica in the liver or lung of humans.
Most of the parasites which live in/on the body of the host do not cause disease (non-pathogenic
parasites). In Medical parasitology we focus on most of the disease causing (pathogenic) parasites.
However, understanding parasites which do not ordinariy produce disease in heathy
(immunocompetent) individuals but do cause illness in individuals with impaired defense mechanism
(opportunistic parasites) is becoming of paramount importance because of the increasing prevaence of
HIV/AIDS in our country.
DIFFERENT KINDS OF HOSTS
Definitive host – a host that harbors a parasite in the adult stage or where the parasite undergoes a
sexual method of reproduction.
Intermediate host - harbors the arval stages of the parasite or an asexual cycle of development takes
pace. In some cases, larval development is completed in two different intermediate hosts, referred to
as first and second intermediate hosts.
Paratenic host – a host that serves as a temporary refuge and vehicle for reaching an obligatory host,
usually the definitive host, i.e. it is not necessary for the completion of the parasites life cycle.
Reservoir host – a host that makes the parasite available for the transmission to another host and is
usually not affected by the infection.
Natural host a host that is naturally infected with certain species of parasite.
Accidental host – a host that is under normal circumstances not infected with th
Meiosis in plant cell system and division.pptReddykumarAv
Meiosis, on the other hand, is used for just one purpose in the human body: the production of gametes—sex cells, or sperm and eggs. Its goal is to make daughter cells with exactly half as many chromosomes as the starting cell.
The sequence of events by which a cell duplicates its genome, synthesizes the other constituents of the cell and eventually divides into two daughter cells is termed cell cycle
Biology lecture 7 how cell divided cell division 2
1. 8- How cell divided
cell division 11
Meiosis; Reduction division
Dr. Siham Gritly
University of Bahri
Dr. Siham Gritly 1
2. Meiosis; Reduction division
That Occurs in Sexually Reproducing
Organisms
• Part of the process of gamete formation,
• consisting of chromosome conjugation and two
cell divisions, in the course of which the diploid
chromosome number becomes reduced to the
haploid.
• Diploid cells have two homologous copies of each
chromosome.
Dr. Siham Gritly 2
4. • Meiosis is used only for the production of
sperm and eggs
Dr. Siham Gritly 4
5. Meiosis has two unique features: synapsis and
reduction division.
• 1- Synapsis
• * The process of pairing throughout the length
of the homologous chromosomes and
exchanging genetic fragments is called
synapsis.
Dr. Siham Gritly 5
7. • 2-Reduction Division
• Reduction division: The first cell division in
meiosis, the process by which germ cells are
formed.
• In reduction division, the chromosome
number is reduced from diploid (46
chromosomes) to haploid (23 chromosomes)
Dr. Siham Gritly 7
9. Meiosis features
• -yields genetically unique haploid daughter
cells (cells with only one member of each
homologous chromosome pair).
• -involves 2 nuclear and cytoplasmic divisions
• -produces 4 haploid cells
Dr. Siham Gritly 9
10. The Sexual Life Cycle
Dr. Siham Gritly 10
1. In the sexual life cycle,
there is an alternation of
diploid and haploid
generations.
2. Normal diploid body
cells are called somatic
cells.
3. Somatic cells arise
from the zygote and are
all genetically identical.
11. Germ-Line Tissues
Dr. Siham Gritly 11
1. Cells that
produce gametes
are called germ-line
tissues.
2. Germ-line cells
will undergo
meiosis to produce
haploid gametes.
12. The stages of meiosis can be broken down into
two main stages, Meiosis I and Meiosis II
• A. Meiosis I can be broken down into four
substages:
• Prophase I,
• Metaphase I,
• Anaphase I
• and Telophase I
• Meiosis I serves to divide the two versions of
each chromosome;
Dr. Siham Gritly 12
13. • B. Meiosis II can be broken down into four
substages:
• Prophase II,
• Metaphase II,
• Anaphase II
• and Telophase II
• meiosis II separates the two replicas of each
chromosome.
Dr. Siham Gritly 13
14. Meiosis I
• The first cell division in Meiosis is known as
Meiosis I.
• The function of Meiosis I is very different
from that of either Mitosis or Meiosis II.
• In both Mitosis 1 and Meiosis II sister
chromatids are separated during anaphase
to produce identical daughter cells.
Dr. Siham Gritly 14
16. • In Meiosis I members of homologous
chromosome pairs are separated.
• This results in the segregation of genes into the
two gametes.
Dr. Siham Gritly 16
17. stages of Meiosis I :
• 1-prophase I occurs as the chromosomes
condense, homologues pair, and crossing over
occurs;
• Prophase; Main event in prophase of M1 is
“crossing over”, also called
“recombination”.
Dr. Siham Gritly 17
18. • In crossing over, homologous chromosomes
pair up, and exchange segments by breaking
and rejoining at identical locations.
• ( Crossing over allows for combinations of
genes that may never have existed previously).
Dr. Siham Gritly 18
19. Crossing over allows for combinations of genes
that may never have existed previously
Dr. Siham Gritly 19
21. • 2-metaphase I involves formation of the
spindle apparatus and alignment of
chromosome pairs along the center of the cell;
Dr. Siham Gritly 21
22. • 3-anaphase I, The centromeres break and
homologous chromosomes separate and pulled
toward the poles (note that the sister
chromatids are still attached)
• Cytokinesis begins
Dr. Siham Gritly 22
23. • 4-telophase I, the chromosomes gather at each
pole and prepare for the second division.
• cleavage furrow formed
• Cytokinesis reaches completion, creating two
haploid daughter cells
Dr. Siham Gritly 23
24. Meiosis II
• Meiosis II, which also has four stages, follows
after meiosis I,
• This result is the separation of the sister
chromatids to form four haploid gametes.
Dr. Siham Gritly 24
25. 4 stages of meiosis11
• * prophase 11, the chromosomes condense
and the spindle forms.
• Centrioles form and move toward the poles
• The nuclear membrane dissolves
Dr. Siham Gritly 25
26. • *Metaphase 11; chromosomes line up singly on the
cell equator.
• Microtubules grow from the centrioles and attach to
the centromeres
• The sister chromatids line up along the cell equator
Dr. Siham Gritly 26
27. • *Anaphase 11; centromeres divide and pulled
to opposite poles.
• The centromeres break and sister chromatids
separate
• Cytokinesis begins
Dr. Siham Gritly 27
28. • *telophase 11; cytoplasm divided into 2 cells.
• The chromosomes may decondense
• Cytokinesis reaches completion, creating four
haploid daughter cell
Dr. Siham Gritly 28
29. Cytokinesis
• the cytoplasmic division of a cell at the end of
mitosis or meiosis, bringing about the separation
into two daughter cells.
• The division of the cytoplasm and the plasma
membrane following the division of the nucleus
resulting into two cells, each having its own
nucleus and cytoplasm surrounded by a plasma
membrane.
• This process begins during the late stage of
mitosis (Telophase) and meiosis (Telophase II).
Dr. Siham Gritly 29