Cell basic unit of life

UNIT I-CELL AND EVOLUTION
▪Introduction
▪Cell theory
▪Whitaker’s kingdom classification
▪Cell organelles, and their functions
▪Homeostasis,
▪Replication and cell Division
▪Tissue differentiation
▪Stem cells and their applications
▪Genetic algorithms

Concept of evolution
• The process by which different kinds of living organism
are believed to have developed from earlier forms during
the history of the earth.
• Jean Baptistae Lamarck (1801)-spontaneous generation
of species according to needs and functionalities of the
mutation
• Charles darwin (1859)- Based on survival of the fittest
mutations
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• Evolution: Biological theory that animals and plants have
their origin in other preexisting types and that the
distinguishable differences are due to modifications in
successive generations.
• Evolution is the result of genetic changes interacting with
natural selection.
• Eg: apes to humans
• In the 19th Century, Charles Darwin a British naturalist
proposed the theory of biological evolution by natural
selection.
– --- species change over time - give rise to new species - share a
common ancestor.
• Natural Selection depends on:
– the environment
– existing heritable variation
– Heritable variation comes from random mutations 4

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Living Organism
• A living organism may be defined as a
complex unit of physicochemical materials
that is capable of self-regulation,
metabolism (The sum total of the biochemical reactions occurring
in an organism is called its metabolism), and reproduction.
• Furthermore, a living organism
demonstrates the ability to interact with its
environment, grow, move, and adapt.

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What Are the Main Characteristics of organisms?
1. Made of CELLS
2. Require ENERGY (food)
3. REPRODUCE (species)
4. Maintain HOMEOSTASIS-
Living organisms regulate their
internal environment to maintain the
relatively narrow range of conditions
needed for cell function.
5. ORGANIZED - meaning they
contain specialized, coordinated
parts. All living organisms are made
up of one or more cells, which are
considered the fundamental units of
life.
6. RESPOND to environment
7. GROW and DEVELOP
8. EXCHANGE materials with
surroundings (water,
wastes, gases)

Five Kingdoms and their chief
characteristics
• The system of assembling organisms into groups or sets on
the basis of likenesses and variances is called classification.
• It simplifies the study of a wide variety of organisms in a very
systematic manner.
• R.H. Whittaker proposed the five-kingdom classification in
1969.
• This classification was based upon certain characters like:
• Mode of nutrition,
• Thallus organization,
• Cell structure,
• Phylogenetic relationships and
• Reproduction. 8

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Five Kingdoms and their chief characteristics
• Unicellular organisms that lack a nucleus and many of the specialized cell
parts, called organelles. Such organisms are said to be prokaryotic (pro
=‘‘before’’; karyotic =‘‘kernel,’’ ‘‘nucleus’’) and consist of bacteria.
• All of the other kingdoms consist of eukaryotic (eu = ‘‘true’’) organisms, which
have cells that contain a nucleus and a fuller repertory of organelles.
• Whitaker’s Five Kingdom Classification ( 1969)

Cell-basic unit of life
• Smallest living form
• Inside the cell some structure transport
• Metabolize
• Respire
• Reproduce (Meiosis)
• Multiply (Mitosis)
• Energy producing
• Keep information 10
Cells are the basic building blocks of all living things. The human body is
composed of trillions of cells. They provide structure for the body, take in
nutrients from food, convert those nutrients into energy, and carry out
specialized functions. Cells also contain the body’s hereditary material and
can make copies of themselves.

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CELL THEORY
• All living things are made of
cells
• Cells are the basic unit of
structure and function in an
organism (basic unit of life)
• Cells come from the
reproduction of existing
cells (cell division)

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Prokaryotes
• Nucleoid region
(center) contains the
DNA
• Surrounded by cell
membrane & cell wall
(peptidoglycan)
• Contain ribosomes
(no membrane) in
their cytoplasm to
make proteins

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Eukaryotes
• Cells that HAVE a
nucleus and
membrane-bound
organelles
• Includes protists,
fungi, plants, and
animals
• More complex type
of cells

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Cell Structure and Function

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Organelles
• Very small (Microscopic) - subcellular structure
• Perform various functions for a cell
• Found in the cytoplasm - the gelatinous liquid that fills the
inside of a cell - composed of water, salts, and various organic molecules.
• May or may not be membrane-bound
Plant Cell

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Cell or Plasma Membrane
Outside
of cell
Inside
of cell
(cytoplasm)
Cell
membrane
Proteins
Protein
channel Lipid bilayer
Carbohydrate
chains
• Composed of double layer of phospholipids
(maintaining appropriate membrane fluidity at various temperatures) and
proteins (integral (membrane transporters) and peripheral (enzymes))
• Surrounds outside of ALL cells
• Controls what enters or leaves the cell (permeable to
ions and organic molecules)
• Living layer

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• Jelly-like substance enclosed
by cell membrane
• Provides a medium for
chemical reactions to take
place
• Contains organelles to carry
out specific jobs
• Found in ALL cells
Cytoplasm of a Cell
cytoplasm

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• Controls the normal
activities of the cell
• Contains the DNA in chromosomes
• Bounded by a
nuclear envelope (membrane) with
pores (a double membrane that encloses the
entire organelle and isolates its contents from the
cellular cytoplasm)
and nuclear matrix a network within the
nucleus that adds mechanical support.
• Usually the largest organelle
• Each cell has fixed
number of chromosomes that carry
genes
• Genes control cell characteristics
The Control Organelle - Nucleus

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Nucleolus
• Inside nucleus – largest
structure in the nucleus
• Cell may have 1 to 3
nucleoli
• Disappears when cell
divides
• Makes ribosomes that
make proteins –
Riobosome biogenesis
• Plays a role in the cell's response to
stress.
• Nucleoli are made
of proteins, DNA and RNA, and form
around specific chromosomal regions
called nucleolar organizing regions.

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Cytoskeleton
• Complex, dynamic network
of interlinking protein
filaments present in
the cytoplasm of all cells.
• Helps cell maintain
cell shape. – extends from
nucleus to cell membrane
• Also help move
organelles around
• Made of proteins
• Microfilaments are
threadlike & made of
ACTIN
• Microtubules are tube-
like and made of
TUBULIN
• Capable of rapid growth or
disassembly dependent on
the cell's requirements.
Cytoskeleton
Microtubules
Microfilaments

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Centrioles
• Found only in animal cells
• Paired structures near
nucleus
• Made of bundle of
microtubules
• Appear during cell division
forming mitotic spindle
• Organization of mitotic spindle
• Completion of cytokinesis.
• Help to pull chromosome
pairs apart to opposite ends
of the cell.

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Mitochondrion
(plural = mitochondria)
• “Powerhouse” of the cell
• Generate cellular energy
(ATP) through aerobic respiration
• More active cells like muscle
cells have MORE
mitochondria
• Both plants & animal cells
have mitochondria
• Site of CELLULAR
RESPIRATION (burning
glucose)

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MITOCHONDRIA
• Surrounded by a DOUBLE
membrane – composed of phospholipid
bilayer and proteins
• Has its own DNA
– Mitochondria come from cytoplasm
in the egg cell during fertilization
– Therefore you inherit your
mitochondria from your mother!
• Folded inner membrane called
CRISTAE (increases surface area
for more chemical reactions)
• Interior called MATRIX
• Play a role in Signaling, cellular
differentiation, and cell death, as well as
maintaining control of the cell
cycle and cell growth.

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Endoplasmic Reticulum - ER
Two kinds of ER ---ROUGH & SMOOTH
• Network of hollow membrane tubules
• Connects to nuclear envelope & cell membrane
• Functions in Synthesis of cell products &
Transport

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Rough Endoplasmic Reticulum (Rough ER)
• Has ribosomes on its surface
• Makes membrane proteins and
proteins for EXPORT out of cell
• Proteins are made by ribosomes
on ER surface
• They are then threaded into the
interior of the Rough ER to be
modified and transported
• Forms an interconnected network of
flattened, membrane-enclosed sacs
known as cisternae (in the RER)

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Smooth Endoplasmic Reticulum
• Smooth ER (tubular structure) lacks
ribosomes on its surface
• Is attached to the ends of
rough ER
• Makes cell products that are
USED INSIDE the cell
• Makes membrane lipids
(steroids)
• Regulates calcium (muscle
cells)
• Destroys toxic substances
(Liver)
Includes nuclear
membrane connected to
ER connected to cell
membrane (transport)

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Ribosomes
• Made of PROTEINS and rRNA
• A ribosome is made from complexes of RNAs and proteins and is
therefore a ribonucleoprotein complex. Each ribosome is composed of
small (30S) and large (50S) components, called subunits, which are bound
to each other
• “Protein factories” for cell
• Join amino acids to make proteins
• Process called protein synthesis
• Can be attached to Rough ER OR Be free (unattached) in
the cytoplasm
🡪

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Golgi Bodies
• Stacks of flattened sacs
• Have a shipping side (trans
face) and receiving side (cis
face)
• Receive proteins made by
ER
• Transport vesicles with
modified proteins pinch off
the ends
• It packages
proteins into membrane-
bound vesicles inside the cell
before the vesicles are sent to
their destination.
Transport
vesicle
CIS
TRANS

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Golgi Bodies
Look like a stack of pancakes
Modify, sort, & package
molecules from ER
for storage OR
transport out of cell

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Lysosomes
• Contain digestive
enzymes
• Break down food,
bacteria, and worn out
cell parts for cells
• Programmed for cell
death (AUTOLYSIS)
• Lyse (break open) &
release enzymes to
break down & recycle
cell parts)

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Lysosome Digestion
• Cells take in food by
phagocytosis - a cellular
process for ingesting and
eliminating particles larger than
0.5 μm in diameter, including
microorganisms, foreign
substances, and apoptotic cells.
• Lysosomes digest the
food & get rid of
wastes
• Besides degradation of
polymers, the lysosome is
involved in various cell
processes, including
secretion, plasma
membrane repair, apoptosis, cell
signaling, and energy metabolism

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Vacuoles
• Fluid filled sacks for storage
• Small or absent in animal cells
• Plant cells have a large Central
Vacuole
• No vacuoles in bacterial cells
• In plants, they store Cell Sap
• Includes storage of sugars,
proteins, minerals, lipids,
wastes, salts, water, and
enzymes

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Chloroplasts
• Found only in producers (organisms
containing chlorophyll)
• Use energy from sunlight to make
own food (glucose)
• Energy from sun stored in the
Chemical Bonds of Sugars
❖Surrounded by DOUBLE membrane
❖Outer membrane smooth
❖Inner membrane modified into sacs
called Thylakoids - help absorb sunlight in
order for photosynthesis to occur.
❖Thylakoids in stacks called Grana &
interconnected
❖Stroma – gel like material
surrounding thylakoids -providing support to
the pigment thylakoids, also contain chloroplast DNA, starch
and ribosomes along with enzymes needed for Calvin cycle.

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Chloroplasts
• Contains its own DNA
• Contains enzymes &
pigments for
Photosynthesis
• Never in animal or
bacterial cells
• Photosynthesis – food
making process

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Homeostasis
• Definition : Maintenance of the relative stability of the physical and
chemical aspects of the internal environment within a range compatible
with cellular function.
• Maintaining a constant internal environment with all that the cells need to
survive (O2, glucose, minerals, ions, and waste removal) is necessary for
individual cells.
• The processes by which the body regulates its internal environment are
referred to as homeostasis.
• Components :1) sensor
2) afferent pathway
3) integration center or comparator
4) efferent pathway
5) effector organ(s)
• Physiological control systems are the nervous system, endocrine
system, and immune system through feedback mechanisms.

Components of Homeostasis
 Sensor - major aim is to sense changes in the body temperature, pH, or oxygen levels.
Eg: sensory nerve cell endings in the skin sense a raise of body temperature, and specialized
cells in the pancreas sense a drop in blood glucose.
 Afferent pathway – if communication flows toward the control center from the
receptor, it is termed an afferent pathway.
Carry nerve impulses into the central nervous system.
 Integration center or comparator – receives information from the sensors
and initiates the response to maintain homeostasis.
The integrating center, generally a region of the brain called the HYPOTHALAMUS, signals
an effector (e.g. muscles or an organ) to respond to the stimuli.
 Efferent pathway – carry nerve impulses away from the central nervous system to
effectors (muscles, glands).
 Effector organ(s) - any organ or tissue that receives information from the integrating
center and acts to bring about the changes needed to maintain homeostasis.
Eg: Kidney, which retains water if blood pressure is too low.
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Receptor
Control
Center
Effector

Homeostatic Control System
 Is a functionally interconnected network of body components that operate
to maintain a given physical or chemical factor in the internal
environment relatively constant around an optimal level.
 Can be classified as:
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Intrinsic (local) Controls
Inherent compensatory
responses of an organ to a
change
Extrinsic Controls
Responses of an organ that are
triggered by factors external to the
organ, namely, by the nervous and
endocrine systems.
Eg: Blood glucose regulation
Eg: Blood vessels can
automatically adjust their own
vascular tone, by dilating
(widening) or constricting
(narrowing), in response to some
change in the environment.

NERVOUS SYSTEM
• The nervous system maintains homeostasis by
controlling and regulating the other parts of the
body.
– A deviation from a normal set point acts as a stimulus to a
receptor, which sends nerve impulses to a regulating
center in the brain. The brain directs an effector to act in
such a way that an adaptive response takes place.
• The nervous system has two major portions: the
central nervous system and the peripheral
nervous system.
• Regulating centers are located in the central
nervous system, consisting of the brain and
spinal cord.
– The hypothalamus is a portion of the brain particularly
concerned with homeostasis; it influences the action of the
medulla oblongata, a lower part of the brain, the autonomic
nervous system, and the pituitary gland.
• The peripheral nervous system consists of the
spinal nerves. The autonomic nervous system
is a part of peripheral nervous system and
contains motor neurons that control internal
organs. It has two divisions, the sympathetic
and parasympathetic systems.
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Extrinsic homeostatic systems

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Nervous System
Central Nervous
System (CNS)
Peripheral Nervous
System
Autonomic Nervous
System
Spinal Nerves
Spinal Cord
Brain
Motor
Neurons
Sympathetic
Systems
Parasympathetic
Systems

ENDOCRINE SYSTEM
• The endocrine system consists of glands which secrete
special compounds called HORMONES into the
bloodstream.
• Each hormone has an effect on one or more target
tissues. In this way the endocrine system regulates the
metabolism and development of most body cells and
body systems.
• For e.g. the endocrine system has sex hormones that
can activate sebaceous glands, development of
mammary glands, alter dermal blood flow, and release
lipids from adipocytes etc besides governing
reproduction.
• In the muscular system, hormones adjust muscle
metabolism, energy production, and growth.
• In the nervous system, hormones affect neural
metabolism, regulate fluid/electrolyte balance and help
with reproductive hormones that influence CNS,
development and behaviors.
• In the cardiovascular system, hormones regulate heart
rate and blood pressure.
• Hormones also have anti-inflammatory effects and
control the lymphatic system.
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• Negative feedback :
A control system that causes
the value of a physiological
measurement to change in
the direction opposite to the
initial deviation from set
point.
Eg: Temperature and blood
glucose regulation
• Positive feedback :
A control system that causes
the value of a physiological
measurement to change in
the same direction as the
initial deviation from set
point.
Eg: Clot formation

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Cell growth, reproduction, and
differentiation

• Cell division is the driving process of reproduction at the cellular level.
• Mitosis - Mitosis is that step in the cell cycle where the newly formed
DNA is separated and two new cells are formed with the same number
and kind of chromosomes as the parent nucleus.
• Meiosis - is the type of cell division that results in four daughter cells,
each with half the number of chromosomes of the parent cell.
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The Cell Cycle
Cell cycle refers to the series of events
that take place in a cell, resulting in
the duplication of DNA and division of
cytoplasm and organelles to produce
two daughter cells.
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The Cell Cycle
• Mitosis and meiosis are
single steps in cell cycle
• G1, S, G2, and M phases
– Cells not in process of
dividing are in G0 phase
– Chromosomes are
duplicated in preparation
for the next round of
division during interphase

A typical eukaryotic cell cycle is
divided into two main phases:-
1. INTERPHASE: resting phase - time during which the cell prepares for
division by undergoing both cell growth and DNA replication.
Divided into 3 phases:
I. G1 phase (Gap 1) – The phase of the cell between mitosis and initiation of
replication of the genetic material of the cell. During this phase, the cell is
metabolically active and continues to grow without replicating its DNA.
 G0 Phase - cells which do not divide further attain an inactive G0 phase (quiescent
phase) after they exit the G1 phase. These cells remain metabolically active but do not
divide unless called upon to do so.
II. S phase (Synthesis) – DNA replication - initial quantity of DNA in the cell = 2N,
after replication = 4N. However the number of chromosomes does not vary, viz., if
the number of chromosomes during G1 phase was 2n, it will remain 2n at the end of S
phase. The centriole also divides into two centriole pairs in the cells which contain
centriole.
III. G2 phase (Gap 2) –During this phase, the RNA, proteins, other macromolecules
required for multiplication of cell organelles, spindle formation, and cell growth are
produced as the cell prepares to go into the mitotic phase. 49

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Control of the Cell Cycle
• The stimuli for entering the cell cycle is in the form of
growth factors and cytokines that are capable of
inducing mitotic divisions
• The cell cycle is highly regulated
– Proteins whose concentrations rise & fall in a controlled
manner
• Cyclin and cyclin-dependent kinases (CDK)
• p53 and pRb
• Inhibitors of CDK
• Internal checkpoints & guardians monitor cell health
• Errors in this process can lead to uncontrollable
growth and cancer

• Cyclin and cyclin-dependent kinases (CDK)
Cyclin is a family of proteins that controls the progression of a cell through
the cell cycle by activating cyclin-dependent kinase (CDK) enzymes or group
of enzymes required for synthesis of cell cycle.
• p53 and pRb
 p53 - main functions are the induction of apoptosis and cell cycle arrest -
to prevent the propagation of cells with serious DNA damage
controls checkpoints throughout the cell cycle from G1 phase to cytokinesis
 pRb - regulates cell proliferation and apoptosis
responsible for a major G1 checkpoint, blocking S-phase entry and cell growth.
• Inhibitors of CDK
The main function of these inhibitors is to block cell cycle and inhibit cell
proliferation by inhibiting the CDK enzyme activity.
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• Cell cycle
control is
focused at 3
places:
• G1 checkpoint
• G2 checkpoint
• M checkpoint
– Before S
phase (DNA
synthesis)
– At transition
between G2
and M phase
Control of the Cell Cycle

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DNA replication-Binary fission
Daughter cells are identical copies
(1) (2) (3)
(4) (5) (6)
Chromosome Plasma membrane
Neither mitosis nor meiosis occurs in prokaryotes
Asexual reproduction by a separation of the body into two new bodies - an
organism duplicates its genetic material (DNA), and then divides into two
parts (cytokinesis), with each new organism receiving one copy of DNA.

Bacteria
Reproduction
Asexual, through binary fission
No true sexual reproduction,
since neither mitosis nor meiosis
exist in prokaryotes
Horizontal transfer of genetic
material
Transformation
Transduction
Conjugation
Uptake of genetic material from
the environment
Transfer of genetic material
between prokaryotes by viruses
Direct transfer of genetic
material from one prokaryote to
another
DNA
cell wall

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2. MITOSIS
• Four phases
–1. Prophase:
chromosomes condense,
spindle apparatus forms,
nuclear envelope breaks
down
–2. Metaphase:
chromosomes line up at
equator of cell
–3. Anaphase: sister
chromatids separate
–4. Telophase: new
nuclear envelopes form,
chromosomes unwind
nuclear
envelope
pair of
homologous,
duplicated
chromosomes
sister
chromatids of
one duplicated
homologue

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(d) ANAPHASE:
Sister chromatids have
separated, and one set has
moved toward each pole.
(a) INTERPHASE in a seed cell:
The chromosomes (blue) are in the
thin, extended state and appear as
a mass in the center of the cell. The
spindle microtubules (red) extend
outward from the nucleus to all
parts of the cell.
(b) LATE PROPHASE:
The chromosomes (blue)
have condensed and
attached to the spindle
microtubules (red).
(e) TELOPHASE:
The chromosomes have
gathered into two clusters,
one at the site of each future
nucleus.
(c) METAPHASE:
The chromosomes have
moved to the equator of the
cell.
(f) Resumption of interphase:
The chromosomes are relaxing
again into their extended state.
The spindle microtubules are
disappearing, and the
microtubules of the two
daughter cells are rearranging
into the interphase pattern.

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Parent Cell
Chromosomes
have been
replicated
Daughter Cells
Each cell has the same
genetic makeup as the
parent cell
Mitosis
Each new nucleus is genetically
identical to the parent nucleus

MEIOSIS
• Meiosis is the process in which a single cell divides twice to form four
haploid daughter cells. These cells are the gametes – sperms in males and
egg in females.
• The process of meiosis is divided into 2 stages. Each stage is subdivided
into several phases.
• Meiosis I:
Prophase I
Metaphase I
Anaphase I
Telophase I
Cytokinesis I
• Meiosis II:
Prophase II
Metaphase II
Anaphase II
Telophase II
Cytokinesis II 61

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Meiosis
Characteristics of meiosis
1. Occurs in sex cells (germ cells) and produces gametes
2. A reductional division resulting in haploid cells
3. Involves two sequential divisions resulting in four
cells
4. Produces cells that are genetically different because
of genetic recombination (crossing-over).

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Meiosis produces gametes for sexual
reproduction
• Multiplies number of cells but also reduces chromosome
number in each daughter cell to exactly half the number
present before meiosis
• Daughter cells get 1 member of each homologous pair, i.e. 1
allele for each gene
• Mitosis produces 2 daughter cells
• Meiosis produces 4 daughter cells
• All body cells in humans are diploid (2n), except gametes
• Cells with 1 member of each homologous pair are haploid (n).

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Parent Cell
(2n)
1st division 2nd division
Daughter Cells (1n)
each chromosome has
2 chromatids
Gamete Cells (1n)
Meiosis

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Cell Differentiation
• The process of altering the pattern of
gene expression and thus becoming a
cell of a particular type is called cell
differentiation.
• Presence of chemicals (or other
influences) starts altering the decisions
as to which genes will be turned on or
off.
• The zygote is a totipotent cell - its
daughter cells can become any cell type.
As the development proceeds, some of
the cells become pluripotent - they can
become many, but not all cell types.
• Later on, the specificity narrows down
further and a particular stem cell can
turn into only a very limited number of
cell types, e.g., a few types of blood
cells, but not bone or brain cells or
anything else. That is why embryonic
stem cell research is much more
promising than the adult stem cell
research.

Differentiation of different tissues and organs
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• Zygote - fertilized egg cell that results from the union of a female gamete (egg, or ovum)
with a male gamete (sperm).
• Blastocyst - The embryo divides and multiplies its cells over 5 to 6 days to become a
blastocyst.
• Morula - The embryo at 16 celled stage is called the morula. It is the mass of cells resulting
from the cleavage of the zygote before the formation of a blastula.
• Blastula - At the 32-cell stage of division, the embryo is known as a blastula that contains
inner cell mass and outer cell mass.
• Gastrula - an embryo at the stage following the blastula, when it is a hollow cup-shaped
structure having three layers of cells – Process - Gastrulation
• Ectoderm - The ectoderm is the outermost germ layer in animals. It gives rise to the skin,
nervous system, and sense organs.
• Mesoderm - Mesoderm is the middle developmental layer between the ectoderm and
endoderm, which gives rise to the skeleton, muscle, heart and bones.
• Endoderm - The endoderm is the innermost layer of the embryo. It develops into various
organs like lungs, liver, lining of GI tract, pancreas.
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Cloning – Dolly the sheep
• Sir Ian Wilmut, (born July 7,
1944, Hampton Lucy,
Warwickshire, Eng.), British
developmental biologist who
was the first to use nuclear
transfer of differentiated adult
cells to generate a
mammalian clone, a Finn
Dorset sheep named Dolly,
born in 1996.
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• Genetic algorithms (GA) in
programming, simulate the process of
natural selection which means those
species who can adapt to changes in their
environment are able to survive and
reproduce and go to next generation.
• In simple words, they simulate “survival of
the fittest” among individual of consecutive
generation for solving a problem.
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• Genetic algorithms are based on an
analogy with genetic structure and
behaviour of chromosomes of the
population.
• Following is the foundation of GAs based
on this analogy –
1. Individual in population compete for
resources and mate
2. Those individuals who are successful
(fittest) then mate to create more offspring
than others
3. Genes from “fittest” parent propagate
throughout the generation, that is
sometimes parents create offspring which
is better than either parent.
4. Thus each successive generation is more
suited for their environment.
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• Genetic operators- selection, crossover, and mutation.
• Selection - process of selecting parents which mate and
recombine to create off-springs for the next generation. Parent
selection is very crucial to the convergence rate of the GA as
good parents drive individuals to a better and fitter solutions.
• Crossover - The crossover operator is analogous to
reproduction and biological crossover. In this more than one
parent is selected and one or more off-springs are produced
using the genetic material of the parents.
• Mutation - mutation may be defined as a small random
tweak in the chromosome, to get a new solution. It is used to
maintain and introduce diversity in the genetic population.
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• Gene represents a single solution to a problem
• chromosome (individual) is composed of several genes or
multiple similar solutions.
• population of individuals are maintained within search space -
all solutions to the problem
Components of a search space in Genetic algorithm
The whole algorithm can be summarized as –
1)Randomly initialize n populations
2)Determine fitness of population
3)Until convergence repeat:
a) Select parents from population
b) Crossover and generate new population
c) Perform mutation on new population
d) Calculate fitness for new population

The Fitness score
• The GAs maintains the population of n individuals
(chromosome/solutions) along with their fitness
scores.
• The individuals having better fitness scores are given
more chance to reproduce than others.
• The individuals with better fitness scores are selected
who mate and produce better offspring by combining
chromosomes of parents.
• Always the new generation of solutions will have
better fitness than the parent population.
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Operators for GA
• The Algorithm uses
certain biological
concepts as operators
to find better solutions
• CrossOver
• Mutation
• Selection ( best
fitness score in
previous generation)
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Crossover
Mutation

Uses of GA
Genetic Algorithms are primarily used in optimization problems of various kinds,
but they are frequently used in other application areas
• Optimization − Genetic
Algorithms are most commonly
used in optimization problems
wherein we have to maximize
or minimize a given objective
function value under a given
set of constraints
• DNA Analysis − GAs have
been used to determine the
structure of DNA using
spectrometric data about the
sample.
• Neural Networks − GAs are
also used to train neural
networks, particularly recurrent
neural networks.
• Parallelization − GAs also
have very good parallel
capabilities, and prove to be
very effective means in solving
certain problems, and also
provide a good area for
research.
87

Advantages-disadvantages of GA
• Does not require any
derivative information (which
may not be available for many
real-world problems).
• Is faster and more efficient as
compared to the traditional
methods.
• Provides a list of “good”
solutions and not just a single
solution.
• GAs are not suited for all
problems, especially problems
which are simple and for which
derivative information is
available.
• Fitness value is calculated
repeatedly which might be
computationally expensive
• Being stochastic, there are no
guarantees on the optimality or
the quality of the solution.
88

Cell basic unit of life

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