Cell division is the process by which a parent cell divides into two or more daughter cells. There are two main types of cell division: mitosis and meiosis. Mitosis produces two identical daughter cells during growth and repair of the body. It ensures the genetic makeup remains the same. Meiosis produces gametes with half the number of chromosomes and involves two cell divisions. It results in genetic diversity that is important for sexual reproduction.
The study of the cell cycle focuses on mechanisms that regulate the timing and frequency of DNA duplication and cell division. As a biological concept, the cell cycle is defined as the period between successive divisions of a cell. During this period, the contents of the cell must be accurately replicated.
The cell cycle is regulated by cyclins and cyclin-dependent kinases.
How long is one cell cycle?
Depends. Eg. Skin cells every 24 hours. Some bacteria every 2 hours. Some cells every 3 months. Cancer cells very short. Nerve cells never.
Programmed cell death:
Each cell type will only do so many cell cycles then die. (Apoptosis)
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.
This presentation explains the topic of CELL CYCLE and CELL DIVISION.
It includes cell mitosis of both Plant cell and Animal cell with labelled diagrams.
The cell cycle, or cell-division cycle, is the series of events that take place in a cell leading to duplication of its DNA (DNA replication) and division of cytoplasm and organelles to produce two daughter cells.
The study of the cell cycle focuses on mechanisms that regulate the timing and frequency of DNA duplication and cell division. As a biological concept, the cell cycle is defined as the period between successive divisions of a cell. During this period, the contents of the cell must be accurately replicated.
The cell cycle is regulated by cyclins and cyclin-dependent kinases.
How long is one cell cycle?
Depends. Eg. Skin cells every 24 hours. Some bacteria every 2 hours. Some cells every 3 months. Cancer cells very short. Nerve cells never.
Programmed cell death:
Each cell type will only do so many cell cycles then die. (Apoptosis)
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.
This presentation explains the topic of CELL CYCLE and CELL DIVISION.
It includes cell mitosis of both Plant cell and Animal cell with labelled diagrams.
The cell cycle, or cell-division cycle, is the series of events that take place in a cell leading to duplication of its DNA (DNA replication) and division of cytoplasm and organelles to produce two daughter cells.
-Cell Division Process In Prokaryotes & Eukaryotes
-Compacting DNA into Chromosomes
-Types of Cell Reproduction
-Phases of the Cell Cycle
-Mitosis
-Meiosis
-Oogenesis & Spermatogenesis
-Comparison of Divisions
OVERVIEW OF CELL CYCLE
Explained in brief phases of cell cycle . Given a explanation of each phase in detail, also explained the significance of meiosis in brief.
This includes detailed description of the Cell Cycle and Cell Cycle regulation. Courtesy: Campbell Biology Book, And Dr, Rosemary Redfield Lectures, University of British Columbia.
mitosis is a part of the cell cycle when replicated chromosomes are separated into two new nuclei. Cell division gives rise to genetically identical cells in which the number of chromosomes is maintained.
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Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
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Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
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AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
MANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdfJim Jacob Roy
Cardiac conduction defects can occur due to various causes.
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Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
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These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
Prix Galien International 2024 Forum ProgramLevi Shapiro
June 20, 2024, Prix Galien International and Jerusalem Ethics Forum in ROME. Detailed agenda including panels:
- ADVANCES IN CARDIOLOGY: A NEW PARADIGM IS COMING
- WOMEN’S HEALTH: FERTILITY PRESERVATION
- WHAT’S NEW IN THE TREATMENT OF INFECTIOUS,
ONCOLOGICAL AND INFLAMMATORY SKIN DISEASES?
- ARTIFICIAL INTELLIGENCE AND ETHICS
- GENE THERAPY
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- ETHICAL CHALLENGES IN LIFE SCIENCES
- Prix Galien International Awards Ceremony
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
2. Contents
• Introduction
• Types of cells
• Types of cell divison
• Cell cycle
• Mitosis
• Meiosis
Meiosis I
Meiosis II
• Applied aspects
3. Introduction
What is it?
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. In eukaryotes, there are two
distinct types of cell division: a vegetative division,
whereby each daughter cell is genetically identical to the
parent cell (mitosis), and a reproductive cell division,
4. • Cell division is an inherent property of living
organisms. It is a process in which cells
reproduce their own kind.
• The growth, differentiation, reproduction and
repair take place through cell division.
• Rudolf Virchow(1858) suggested ”Omnis
cellula e cellula” means every cell is derived
from pre existing cell.
• There are two types of cell division namely
Mitosis and Meiosis.
5. • The cell (from Latin cella, meaning "small
room")
• The basic structural, functional, and biological
unit of all known living organisms.
• A cell is the smallest unit of life that
can replicate independently, and cells are often
called the "building blocks of life".
• Prokaryote is a single-celled organism that
lacks a membrane-
bound nucleus (karyon), mitochondria, or any
other membrane-bound organelle.
7. Cell cycle
•The cell cycle is the sequence of events or changes that occur
between the formation of cell and its division into daughter cells.
•It has a nondividing, growing phase called Interphase and
dividing phase called mitotic or M-phase.
8.
9. Interphase ( inter – between, phases – aspect)
:metabolically active phase
• Longest phase in the cell cycle
• Cell grows in size
• Doubles cytoplasmic organelles
• Duplicates chromosomes
• Three stages: G1, S, G2
1. G1: cell growth
2. S: synthesis of DNA (chromosome duplication)
3. G2: cell growth and preparation for division
10. G1 Phase or GAP 1 Phase :
• Period in the cell cycle during interphase, after
cytokinesis and before the S phase.
• The cell is metaboically active,
• There is great amount of protein and enzymes
synthesis,
• There is NO DNA REPLICATION
S-Phase or Synthesis Phase :
• Period in the cell cycle during interphase,
between G1 phase and the G2 phase.
• DNA synthesis or replication occurs.
11. G2 Phase or GAP 2 Phase:
• The final, and usually the shortest phase during
interphase
• Cell undergoes a period of rapid growth to prepare for M
phase.
• The nucleus is well defined, bound by a nuclear
envelope and contains at least one nucleolus.
• At the end of this phase is a control checkpoint (G2
checkpoint) to determine if the cell can proceed to enter
M phase and divide.
• G2 checkpoint prevents cells from entering mitosis with
DNA damaged since the last division, providing an
opportunity for DNA repair and stopping the proliferation
of damaged cells so that the G2 checkpoint helps to
maintain genomic stability
G 0 Phase (Quiescent stage) :
• Period in the cell cycle where cells do not divide further
and exist in a quiescent state.
12. Mitotic or M-phase
• The most dramatic period of the cell cycle,
involving a major reorganisation of virtually all
components of the cell.
• Since the number of chromosomes in the
parent and progeny cells is the same, it is also
called as equational division.
• It includes two important processes that occur
simultaneously.
Karyokinesis (division of the nucleus)
Cytokinesis (division of the cytoplasm)
• Resulting in two daughter cells.
13. Mitosis
(Gr. Mitos – thread, osis – stage)
• Walter Flemming (1882) studied mitotic cell
division in animal cells and coined the term
mitosis.
• Mitosis is a type of cell division in which a parental
cell produces two similar daughter cells that
resemble the parental cell in terms of
chromosomal number. Hence called Equational
cell division (homotypic cell division).
• This maintains constant number of chromosomes
in each cell of successive generation.
• It occurs in somatic cells of the body. Also called
14. Karyokinesis (Karyon – nucleus, kinesis –
movement)
The division of nuclear material.
• Occurs in four stages
1. Prophase (Gr. Pro – before, phases –
appearance)
2. Metaphase (Meta – after, phase –
appearance)
3. Anaphase (ana – up, phases - appearance)
4. Telophase (Telo – end, phases –
appearance)
15. Prophase (Gr. Pro – before, phases –
appearance)
• It is the longest phase.
• The chromatin is organized into distinct
chromosomes by coiling or spiralization.
• The centrioles develop into asters and move
towards the opposite poles of the cell to
establish the plane of cell division.
• Spindle apparatus begin to appear
• Nucleolus and Nuclear membrane disintegrate
and disappear
• The chromosomes are set free in the
16. Centromere : It is the primary constriction in chromosome to which
the spindle fibres attach during mitotic and meiotic division. It appears
as a constriction when chromosomes contract during cell division.
After chromosomal duplication, which occurs at the beginning of
every mitotic and meiotic division, the two resultant chromatids are
joined at the centromere.
Spindle fibres : It is a group of microtubules that extend from the
centromere of chromosomes to the poles of the spindle or from pole
to pole in a dividing cell.
Sister chromatids : During S phase of the cell cycle the DNA is
replicated and an identical copy of the chromatid is made. These
identical copy of chromatids are called sister chromatids.
17.
18. Metaphase (Meta – after, phase –
appearance)
• Spindle fibres are completely formed
• The chromosome become short and thick with
two distinct chromatids each
• All the chromosomes move towards the centre
of the cell and arrange in the equatorial plane,
right angles to the position of asters to form
metaphasic plate
• Chromosomes are attached to spindle fibres at
their centromeres
19. Metaphase plate :
The plane of the equator (a plane that is equally
distant from the two spindle poles) of the
spindle into which chromosomes are positioned
during metaphase
20.
21. Anaphase (ana – up, phases - appearance)
• The centromere of all the chromosomes undergo
longitudinal splitting and the chromatids of each
chromosome separate to form daughter chromosomes
• The daughter chromosomes move toward the
opposite poles from the equator by the activity of
spindle fibres
22.
23. Telophase (Telo – end, phases –
appearance)
• During this, the events of prophase will be
reversed
• The daughter chromosomes reach the opposite
poles
• The chromosomes undergo despiralization to form
long, thin thread like structures called chromatin
• Nucleolus and nuclear membrane reappears
• The spindle fibres disappear
24.
25. Cytokinesis (cyto – cell, kinesis –
movement)
The Division of cytoplasm
• A cleavage furrow develops in the middle of the
cell in centripetal direction due to the
contraction of microtubules.
• It occurs till the edges of the plasma membrane
meet.
• They fuse to form a separate membrane.
27. Significance of Mitosis:
• It maintains genetic stability within
the population of cells derived
from same parental cell
• It helps the growth and tissue
repair
• It helps in the replacement of dead
and worn out cells
• It is a means of reproduction in
28. SUMMARY
• Type of cell division which takes places during
growth, repair and replacement.
• Takes place in somatic cells.
• Basis of asexual reproduction.
• Daughter cells identical in chromosome
number and genetic make-up at the parent
cell.
• Ensures consistency of genetic information in
nuclei of cells of one individual.
• Chromosomes don’t arrange themselves
along equator in homologous pairs during
metaphase.
29.
30. • Derived from the Greek word meaning
'lessening'.
• The term meiosis (originally spelled "maiosis")
was introduced to biology by J.B. Farmer
and J.E.S. Moore in 1905
• This is a special method of cell division,
occurring in maturation of the sex cells, by
means of which each daughter nucleus
receives half the number of chromosomes
characteristic of the somatic cells of the
species.
31. • Meiosis I is initiated after the parental
chromosomes have replicated to produce
identical sister chromatids at the S phase.
• Meiosis involves pairing of homologous
chromosomes and recombination between
them.
• Four haploid cells are formed at the end of
meiosis II.
• Homologous Chromosomes :
Homologous chromosomes are
chromosomes in a biological cell that pair
(synapse) during meiosis and contain the
32. Sequence Of Events
Meiosis I
(reductional division)
Karyokinesis I
Prophase I
a) Leptotene
b)Zygotene
c)Pachytene
d)Diplotene
e)Diakinesis
Metaphase I
Anaphase I
Telophase I
Cytokinesis I
Meiosis II
(mitotic meiosis)
Karyokinesis
II
Prophase II
Metaphase II
Anaphase II
Telophase II
Cytokinesis II
33. MEIOSIS I
It is reductional division in which a
diploid parental cell produces two
haploid daughter cells. Hence it is
called reductional division
34. Prophase I; longest phase (5
stages)
a) Leptotene: (bouquet stage)
• The chromatin condenses to form chromosomes
• The chromosomes appear as long, thin and thread
like structures. They undergo coiling and become
short and thick.
• Each chromosome has two chromatids that are not
distinctly visible.
• Each chromosome shows bead like structures
called chromomeres.
• The telomeric ends of all the chromosomes
converge towards one side of nuclear membrane;
35. b) Zygotene (Zipper stage):
• Pairing of homologous chromosomes takes place
called synapsis. The pair is called bivalent.
• The chromosome continues to undergo
condensation and asters keep moving towards
opposite poles.
c) Pachytene (Tetrad stage):
• The chromosomes become more short and thick
• Each bivalent shows four chromatids called tetrad
• In this stage the exchange of genetic material
takes place between the non sister chromatids of
homologous chromosomes.
• This process is called genetic crossing over.
• This results in genetic recombination which is
36. d) Diplotene:
• The chiasma move towards the tips of
chromosomes as the homologous
chromosomes of bivalent start moving apart.
This event is called Terminalisation
e) Diakinesis:
• The chromosomes at this stage appear thick,
short and distinct
• The tips of some chromosome show chiasma
• Nucleolus and Nuclear membrane disappear
37.
38. Synapsis: Pairing of the homologous
chromosomes is called Synapsis
Bivalent: A paired unit formed of homologous
chromosomes consisting of a paternal and a
maternal chromosome is called Bivalent
Tetrad: Each homologous chromosome pair
(bivalent) shows four chromatids called tetrad
Crossing over: Exchange of identical parts
between the nonsister chromatids of
homologous chromosomes is called Crossing
over.
Chiasma: These are the regions on homologous
39. Metaphase-I
• Chromosomes are arranged in the equatorial
region with their centromeres towards the poles
and arms towards the equator.
40. Anaphase-I
• The Centromeres do not under go longitudinal
splitting
• The chromosome of each homologous pair
move towards opposite poles by the activity of
spindle fibres. This is called separation or
disjunction of chromosomes.
41. Telophase-I
• The homologous chromosomes separate and reach the
opposite poles
• The nuclear membrane reappears around the
chromosomes at each pole
• The spindle fibres disappear
• Cytokinesis occurs
42. Cytokinesis 1-
It is the division of cytoplasm.
Interkinesis-
The Interphase after the first meiotic division
is called Interkinesis.
It may be present or absent between meiosis-I
and meiosis-II.
If present it may be short or in some cases
telophase-I directly enters to prophase-II.
It is similar to Interphase except for the
absence of replication of DNA.
43. Meiosis II
Occurs soon after meiosis-I.
There is no duplication of
chromosomes.
Hence called mitotic meiosis
44. Prophase-II
• The chromosomes start condensing again
• Spindle apparatus begin to appear
• The nuclear envelope and nucleolus
disintegrate and disappear
45. Metaphase-II
• The Chromosomes arrange in the equatorial
region at right angles to the asters
• The Spindle fibres connect to the centromere.
46. Anaphase-II
• The centromeres of all the chromosomes undergo
longitudinal splitting.
• The chromatids of each chromosome separate and
they move towards opposite poles.
47. Telophase-II
• The chromosomes arrive at the poles and undergo
decondensation to become thin and long chromatin fibres.
• A nuclear envelope is formed.
• Nucleolus also appears
• The spindle fibres disappear
50. Significance of Meiosis
• It helps to restore diploidy and maintain
the constant number of chromosomes for
a species.
• Meiosis produces new combination of
chromosomes and genes by crossing over
and by a random distribution of paternal
and maternal chromosomes to daughter
cells.
51. SUMMARY
• Location - gonads.
• Reduction division - results in halving number
chromosomes.
• Cell division involved in gamete production.
• Four daughter cells formed. Male - all four
develop. Female - three abort, one develops.
• Two divisions occur.
• Chiasma formation leading to crossing over occurs
prophase I resulting in a mixing of genetic material
of the chromosomes.
• Metaphase I - bivalents arrange themselves on
equator of cell. Results in further variation as
random which may position themselves.
• Anaphase I - chromosomes separate.
52.
53. Applied aspects
Defective Mitotic Division
• It usually results in the production of
uncontrolled growth of cells or defective cells.
• Uncontrolled Mitosis
• If the genes that regulate the cell cycle are
damaged or mutated, cell divides abnormally or
may lead to uncontrolled cell growth.
• Cause may be due to Harmful ray: nuclear
radiation, UV ray, Viruses, Carcinogenic
chemicals: food additives, benzo (α) pyrene in
54. Micronuclei
• Micronuclei are extranuclear cytoplasmic bodies.
• They are induced in cells by numerous genotoxic agents that
damage the chromosomes.
• The damaged chromosomes, in the form of acentric
chromatids or chromosome fragments, lag behind in
anaphase when centric elements move towards the spindle
poles.
• After telophase, the undamaged chromosomes, as well as the
centric fragments, give rise to regular daughter nuclei. The
lagging elements are included in the daughter cells, too, but a
considerable proportion is transformed into one or several
secondary nuclei, which are, as a rule, much smaller than the
principal nucleus and are therefore called micronuclei.
• Bigger micronuclei result from exclusion of whole
chromosome following damage to the spindle apparatus of
the cell, whereas smaller micronuclei result from structural
aberrations; causing chromosomal fragments.
55.
56. Defective Meiotic Division
• Defective meiotic divisions usually result in the
production gametes with chromosomal
numerical abnormalities
• Down Syndrome - trisomy of chromosome 21
• Patau Syndrome - trisomy of chromosome 13
• Edward Syndrome - trisomy of chromosome
18
• Klinefelter Syndrome - extra X chromosomes
in males - i.e. XXY, XXXY, XXXXY, etc.
• Turner Syndrome - lacking of one X
chromosome in females - i.e. X0
57. References
• http://www.biologyreference.com/Gr-Hi/History-of-
Biology-Cell-Theory-and-Cell-
Structure.html#ixzz4FChB53a6
• Journal of Oral and Maxillo Facial Pathology Vol.
12 Issue 1 Jan - Jun 2008. Clinico-pathological
correlation of micronuclei in oral squamous cell
carcinoma by exfoliative cytology .Devendra H
Palve, Jagdish V Tupkari.
• Vander’s human physiology 8th edition
• Kahel-frotcher- atlas of human anatomy 10TH
edition.
• Color Atlas of Cytology, Histology, and Microscopic
Anatomy4th edition, revised and Enlarged