Cell - structure and functions

DISCOVERY OF CELL
•1665 – ROBERT HOOKE EXAMINED A THIN SLICE OF CORK
•1674 – ANTON VON LEEUWENHOEK -IMPROVED MICROSCOPE,
OBSERVED MANY LIVING CELLS
•LOOKED AT CELLS IN POND WATER AND BLOOD AND PUBLISHED
HIS OBSERVATIONS

HISTORY OF CELL THEORY
•1850 – RUDOLF VIRCHOW
PROPOSED THAT ALL CELLS COME FROM EXISTING CELLS

•1838 – SCHLEIDEN – ALL PLANTS ARE MADE OF CELLS
•1839 – SCHWANN – ALL ANIMALS ARE MADE OF CELLS

DEFINITION OF CELL
•A CELL IS THE SMALLEST UNIT THAT IS CAPABLE OF PERFORMING
LIFE FUNCTIONS.

MICROSCOPY TODAY: COMPOUND LIGHT
MICROSCOPE
•CAN OBSERVE LIVING CELLS IN TRUE COLOR
•MAGNIFICATION OF UP TO ~1000X
•RESOLUTION ~ 0.2 MICRONS – 0.5 MICRONS

COMPOUND LIGHT MICROSCOPE
7
eye
amoeba, lightmicrograph
lightrays
ocularlens
objectivelens
specimen
condenserlens
lightsource
a.Compoundlightmicroscope
85 µm
© Robert Brons/Biological Photo Service
Copyright© TheMcGraw-HillCompanies,Inc.Permissionrequiredforreproductionordisplay.

MICROSCOPY TODAY:
ELECTRON MICROSCOPE
•MAGNIFICATION UP TO ~100,000
•TRANSMISSION ELECTRON MICROSCOPE (TEM)
•2-D IMAGE
•SCANNING ELECTRON MICROSCOPE (SEM)
•3-D IMAGE

TRANSMISSION ELECTRON MICROSCOPE
9
electronsource
electronbeam
b.Transmissionelectronmicroscope
specimen
200nm
pseudopod segment,transmissionelectron
micrograph
observationscreen
or
photographicplate
electromagnetic
objectivelens
electromagnetic
condenserlens
electromagnetic
projectorlens
© M. Schliwa/Visuals Unlimited

SCANNING ELECTRON MICROSCOPE
10
amoeba,scanningelectronmicrograph
electrongun
electronbeam
electromagnetic
condenser
lenses
scanningcoil
final
condenser
lens
secondary
electrons
specimen
electron
detector
c. Scanningelectronmicroscope
500 m
TV
viewing
screen
© Kessel/Shih/Peter Arnold, Inc.
µ

MICROSCOPY TODAY: IMMUNOFLUORESCENCE LIGHT
MICROSCOPE
•ANTIBODIES DEVELOPED AGAINST A SPECIFIC
PROTEIN
•FLUORESCENT DYE MOLECULE ATTACHED TO ANTIBODY
MOLECULES
•SPECIMEN EXPOSED TO FLUORESCENT ANTIBODIES
•ULTRA-VIOLET LIGHT (BLACK LIGHT) PASSED
THROUGH SPECIMEN
•FLUORESCENT DYE GLOWS IN COLOR WHERE ANTIGEN
IS LOCATED
•EMITTED LIGHT IS FOCUSED BY GLASS LENSES ONTO
HUMAN RETINA
•ALLOWS MAPPING DISTRIBUTION OF A SPECIFIC
PROTEIN IN CELL
11

MICROSCOPY TODAY: CONFOCAL MICROSCOPY
•NARROW LASER BEAM SCANNED ACROSS
TRANSPARENT SPECIMEN
•BEAM IS FOCUSED AT A VERY THIN PLANE
•ALLOWS MICROSCOPIST TO OPTICALLY SECTION A
SPECIMEN
• SECTIONS MADE AT DIFFERENT LEVELS
• ALLOWS ASSEMBLY OF 3D IMAGE ON COMPUTER SCREEN
THAT CAN BE ROTATED
12

TWO TYPES OF CELLS
•PROKARYOTIC
•EUKARYOTIC

PROKARYOTIC
•DO NOT HAVE INTERNAL
STRUCTURES/ ORGANELLES
SURROUNDED BY MEMBRANES
•FEW INTERNAL STRUCTURES
•ONE-CELLED ORGANISMS, BACTERIA
http://library.thinkquest.org/C004535/prokaryotic_cells.html

EUKARYOTIC
•CONTAIN ORGANELLES SURROUNDED BY MEMBRANES
•MOST LIVING ORGANISMS
Animal cell
http://library.thinkquest.org/C004535/eukaryotic_cells.html

“TYPICAL” ANIMAL CELL
http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif

•HUMAN (ALL EUKARYOTIC ) CELL CONSISTS OF NUCLEUS
AND CYTOPLASM
•CYTOPLASM CONTAINS A NUMBER OF ORGANELLES EACH
WITH A DEFINED FUNCTION .

TRADITIONAL CLASSIFICATION OF CELLS
•1-EPITHELIAL CELLS
•2-CONNECTIVE TISSUE OR MESENCHYME
CELL

EPITHELIAL CELL
•CHIEF FEATURES - CELLS ARE CLOSELY
CONTIGUOUS TO ONE ANOTHER
•COVER SURFACE –EX: SKIN
•LINE CAVITIES- EX: MOUTH
•FUNCTION-PROTECTIVE FUNCTION
•SECRETORY FUNCTION- IN RESPIRATORY
EPITHELIUM-SECRETES MUCUS

MESENCHYME CELL
•CHIEF FEATURES -CELLS ARE WIDELY SEPARATED FROM EACH
OTHER BY A ZONE WHICH CONTAIN GROUND SUBSTANCE IN
WHICH COLLEGEN FIBRES EMBEDDED
•FUNCTION –SUPPORTIVE
•FLATTENED ENDOTHELIAL CELLS WHICH LINE BLOOD &LYMPH
VESSELS CONSIDERED TO BE CONNECTIVE TISSUE BUT
PERFORMING A COVERING FUNCTION

EUKARYOTIC CELLS
•STRUCTURES IN ALL EUKARYOTIC CELLS
•NUCLEUS
•RIBOSOMES
•ENDOMEMBRANE SYSTEM
•ENDOPLASMIC RETICULUM – SMOOTH AND ROUGH
•GOLGI APPARATUS
•VESICLES
•MITOCHONDRIA
•CYTOSKELETON

CYTOSKELETON
MITOCHONDRION
CENTRIOLES
LYSOSOME
GOLGI BODY
SMOOTH ER
ROUGH ER
RIBOSOMES
NUCLEUS
PLASMA
MEMBRANE
Fig. 4-15b, p.59

Electron Micrograph of organelles in a hepatocyte (liver cell).

CELL MEMBRANE
•ALL CELLS ARE BOUNDED BY AN EXTERNAL LIPID MEMBRANE CALLED
PLASMA MEMBRANE OR PLASMALEMMA .
•SERVES AS A DYNAMIC INTERFACE WITH EXTERNAL ENVIRONMENT.
•CELL INTERACT WITH TWO TYPE OF EXTERNAL ENVIRMENT-
o1-ADJACENT CELL -SEPARATED BY INTERCELLULAR SPACE (IC)
o2-EXTRACELLULAR MATRIX –COLLAGEN FIBRILS (F)

•CELL MEMBRANE CONSISTS OF BILAYER OF PHOSPHOLIPID
MOLECULE THAT ARE AMPHIPATHIC.
•CONSIST OF 1-POLAR –HYDROPHILIC (WATER LOVING )HEAD-
•DERIVED FROM GLYCEROL CONJUGATED TO A NITROGENOUS
COMPOUND EG CHOLIN ,ETHANOLAMINE VIA A PHOSPHATE
BRIDGE .
•2-NONPOLAR –HYDROPHOBIC ( WATER HATING )TAIL
•CONSIST OF TWO LONG CHAIN FATTY ACID EACH COVALENTLY
LINKED TO GLYCEROL COMPONENT OF POLAR HEAD.

•PROTEIN MOLECULE MAKE UP ALMOST HALF OF TOTAL MASS OF MEMBRANE
•1-INTRNSIC OR INTREGRAL PROTEIN –PROTEIN MOLECULE INCORPORATED
WITHIN MEMBRANE
•2-EXTRINSIC OR PERIPHERAL PROTEIN –HELD TO THE INNER OR OUTER
SURFACE BY WEAK ELECTRONIC FORCE
•3- TRANSMEMBRANE PROTEIN-INTRINSIC PROTEIN SPANNING THE ENTIRE
THICKNESS OF MEMBRANE –ALLOWS THE PROTEIN TO FLOAT FREELY IN THE
PLANE OF MEMBRANE.
•FUNCTION- CELL-CELL ADHESION, CELL MATRIX ADHESION,
COMMUNICATION AND FORMATION OF PORES OR CHANNELS FOR
TRANSPORT OF MATERIAL INTO AND OUT OF CELL.

FLUID MOSAIC OF MEMBRANE STRUCTURE

Electron micrograph and sketch of plasma membrane
surrounding a human red blood cell.
Membrane structure

NUCLEUS
•NUCLEUS IS CONTROL CENTER OF THE CELL
•LARGEST ORGANELLE IN THE CELL
•1. MEMBRANE BOUND (NUCLEAR ENVELOPE)
•2. CONTAINS NUCLEOLI; SYNTHESIZES RIBOSOMAL RNA
•3. DNA IS IN CHROMOSOMES (DNA AND PROTEINS
(NULEOPROTEIN)

NUCLEOPROTEIN
•TWO MAJOR TYPE
•1-HISTONE PROTEIN –LOW MOLECULAR WEIGHT POSITIVELY CHARGED
•FUNCTION- BIND TIGHTLY TO DNA AND CONTROL THE COILING AND
EXPRESSION OF GENES ENCODED BY DNA STRAND
•2-NON HISTONE PROTEIN- INCLUDING ENZYME FOR SYNTHESIS OF DNA
AND REGULATORY PROTEIN
•ALL NUCLEOPROTEINS ARE SYNTHESISED IN CYTOPLASM AND IMPORTED
INTO NUCLEUS.

NUCLEI
•HETEROGENEOUS STRUCTURE WITH ELECTRON DENSE (DARK AREA)
CALLED HETEROCHROMATIN H , AND ELECTRON LUCENT (LIGHT AREA)
CALLED HETEROCHROMATIN E.
•HETEROCHROMATIN H –CONSIST OF TIGHTLY COILED INACTIVE
CHROMATIN FOUND IN IRREGULAR CLUMPS OFTEN AROUND THE
PERIPHERY OF NUCLEUS.
•EUCHROMATIN E REPRESENT PART OF DNA THAT IS ACTIVE IN RNA
SYNTHESIS.

NUCLEAR ENVELOPE
•ENCLOSE THE NUCLEUS
•CONSIST OF TWO LAYER WITH
INTERMEMBRANOUS OR PERINUCLEAR SPACE
•INNER AND OUTER NUCLEAR MEMBRANE HAVE
TYPICAL PHOSPHOLIPID BILAYER STRUCTURE
WITH DIFFERENT INTEGRAL PROTEIN.

•OUTER LIPID BILAYER CONTINUOUS WITH ENDOPLASMIC RETICULUM AND
HAS RIBOSOME ON ITS CYTOPLASMIC FACE
•INNER ASPECT OF INNER NUCLEAR MEMBRANE –THERE IS AN ELECTRON
DENSE LAYER OF INTERMEDIATE FILAMENTS ,NUCLEAR LAMINA THAT LINKED
INNER MEMBRANE PROTEIN AND HETEROCHROMATIN H .
•NUCLEAR ENVELOP CONTAIN NUMEROUS NUCLEAR PORE FUNCTION 0F
PORE- PERMITS AND REGULATE THE EXCHANGE OF METABOLITES
,MACROMOLECULES AND ,RIBOSOMAL SUBUNIT B/W NUCLEUS AND
CYTOPLASM.
 NUCLEOPLASM – FLUID OF THE NUCLEUS

Nuclear pore bilayer facing cytoplasm Nuclear envelope
bilayer facing
nucleoplasm
Fig. 4-17, p.61

CHROMATIN
•CHROMOSOMAL MATERIAL OF THE NON-MITOTIC CELLS.
•CONSISTS OF DNA, HISTONE, NONHISTONE PROTEIN & SMALL
AMOUNT OF RNA
•CHROMATIN CONDENSES TO FORM CHROMOSOMES DURING CELL
DIVISION.
•E/M-CHROMATIN IS VISIBLE AS THIN FIBER (APP,200 A) ARRANGED
IN MESHWORK.

DNA
•DOUBLE HELIX COMPOSED OF FOUR DEOXY-
RIBONUCLEOTIDES
(BASE+ SUGAR+ PHOSPHATE),
POLYMERIZED IN AN UNBRANCHED MANNER.
•DNA IS PACKED IINTO THE NUCLEUS IN A SPECIFIC
PATTERN

NUCLEOLUS
•AREA OF CONDENSED DNA
•RIBOSOMAL RNA AND PROTEIN SYNTHESIS IN THE CYTOPLASM
AND IMPORTED INTO NUCLEUS ARE ASSEMBLED INTO SUBUNIT.
•SUBUNIT-PASS BACK TO CYTOPLASM TO AGGREGATE INTO
COMPLETE RIBOSOME .
•NUCLEOLUS CONSISTS OF RETICULAR NUCLEOLEMMA WITH DENSE
FILAMENTOUS COMPONENT F AND POLAR GRANULAR COMPONENT
G

•FILAMENTOUS COMPONENT-SITE OF RIBOSOMAL RNA
SYNTHESIS
•GRANULAR COMPONENT- TAKE PLACE IN RIBOSOME
ASSEMBLY.

nuclear
pores
chromatin
nucleolus
nuclear
envelope

ENDOMEMBRANE SYSTEM
•SERIES OF ORGANELLES RESPONSIBLE
FOR:
•MODIFYING PROTEIN CHAINS INTO THEIR
FINAL FORM
•SYNTHESIZING OF LIPIDS
•PACKAGING OF FULLY MODIFIED
PROTEINS AND LIPIDS INTO VESICLES
FOR EXPORT OR USE IN THE CELL

ENDOMEMBRANE SYSTEM
•ENDOPLASMIC RETICULUM (ER)
•CONTINUOUS WITH THE OUTER
MEMBRANE OF THE NUCLEAR ENVELOPE
•TWO FORMS - SMOOTH AND ROUGH
•TRANSPORT VESICLES
•GOLGI APPARATUS

ENDOPLASMIC RETICULUM
•ROUGH ENDOPLASMIC RETICULUM (RER)
•NETWORK OF FLATTENED MEMBRANE
SACS CREATE A “MAZE”
•RIBOSOMES ATTACHED TO THE OUTSIDE
OF THE RER MAKE IT APPEAR ROUGH

ENDOPLASMIC RETICULUM
•FUNCTION RER
•WHERE PROTEINS ARE MODIFIED AND
PACKAGED IN TRANSPORT VESICLES FOR
TRANSPORT TO THE GOLGI BODY

0.5 micrometers
ribosomes
rough endoplasmic reticulum

ENDOMEMBRANE SYSTEM
•SMOOTH ER (SER)
•TUBULAR MEMBRANE STRUCTURE
•CONTINUOUS WITH RER
•NO RIBOSOMES ATTACHED
•FUNCTION SER
•SYNTHESIS OF LIPIDS (FATTY ACIDS, PHOSPHOLIPIDS,
STEROLS..)

ENDOMEMBRANE SYSTEM
•ADDITIONAL FUNCTIONS OF THE SER
•IN MUSCLE CELLS, THE SER STORES CALCIUM IONS AND
RELEASES THEM DURING MUSCLE CONTRACTIONS
•IN LIVER CELLS, THE SER DETOXIFIES MEDICATIONS AND
ALCOHOL

GOLGI APPARATUS
•GOLGI APPARATUS
•STACK OF FLATTENED MEMBRANE SACS
•FUNCTION GOLGI APPARATUS
•COMPLETES THE PROCESSING SUBSTANCES RECEIVED FROM THE
ER
•SORTS, TAGS AND PACKAGES FULLY PROCESSED PROTEINS AND
LIPIDS IN VESICLES

GOLGI APPARATUS
•GOLGI APPARATUS RECEIVES TRANSPORT VESICLES
FROM THE ER ON ONE SIDE OF THE ORGANELLE
•VESICLE BINDS TO THE FIRST LAYER OF THE GOLGI AND
ITS CONTENTS ENTER THE GOLGI

GOLGI APPARATUS
•THE PROTEINS AND LIPIDS ARE MODIFIED AS THEY PASS
THROUGH LAYERS OF THE GOLGI
•MOLECULAR TAGS ARE ADDED TO THE FULLY MODIFIED
SUBSTANCES
•THESE TAGS ALLOW THE SUBSTANCES TO BE SORTED AND
PACKAGED APPROPRIATELY.
•TAGS ALSO INDICATE WHERE THE SUBSTANCE IS TO BE
SHIPPED.

TRANSPORT VESICLES
•TRANSPORT VESICLES
•VESICLE = SMALL MEMBRANE BOUND SAC
•TRANSPORT MODIFIED PROTEINS AND LIPIDS FROM THE
ER TO THE GOLGI APPARATUS (AND FROM GOLGI TO FINAL
DESTINATION)

VESICLES
•VESICLES - SMALL MEMBRANE BOUND SACS
•EG:
•GOLGI AND ER TRANSPORT VESICLES
•PEROXISOME
•WHERE FATTY ACIDS ARE METABOLIZED
•WHERE HYDROGEN PEROXIDE IS DETOXIFIED
•LYSOSOME

LYSOSOMES•THE LYSOSOME IS AN EXAMPLE OF AN ORGANELLE MADE AT THE
GOLGI APPARATUS.
•GOLGI PACKAGES DIGESTIVE ENZYMES IN A VESICLE. THE VESICLE
REMAINS IN THE CELL AND:
•DIGESTS UNWANTED OR DAMAGED CELL PARTS
•MERGES WITH FOOD VACUOLES AND DIGEST THE CONTENTS
•LY1-VARYING IN SIZE MEM. BOUND ORGANELLES ,CONTAIN AMORPHOUS
GRANULAR MATERIAL
•LY2-ELECTRON DENSE PHAGOLYSOSOME

MITOCHONDRIA
• FUNCTION – SYNTHESIS OF ATP
• 3 MAJOR PATHWAYS INVOLVED IN ATP PRODUCTION
1. GLYCOLYSIS
2.KREBS CYCLE
3.ELECTRON TRANSPORT SYSTEM (ETS)

MITOCHONDRIA
•STRUCTURE:
•~1-5 MICRONS
•OUTER MEMBRANE
•INNER MEMBRANE - HIGHLY FOLDED
•FOLDS CALLED CRISTAE
•INTERMEMBRANE SPACE (OR OUTER COMPARTMENT)
•MATRIX
•DNA AND RIBOSOMES IN MATRIX

VACUOLES
•VACUOLES ARE MEMBRANE SACS THAT ARE
GENERALLY LARGER THAN VESICLES.
•EXAMPLES:
•FOOD VACUOLE - FORMED WHEN FOOD IS BROUGHT INTO THE
CELL BY ENDOCYTOSIS
•CONTRACTILE VACUOLE – COLLECT AND PUMP EXCESS WATER
OUT
•CENTRAL VACUOLE – COVERED LATER

CYTOSKELETON
•FUNCTION
•GIVES CELLS INTERNAL ORGANIZATION, SHAPE, AND ABILITY TO
MOVE
•STRUCTURE
•INTERCONNECTED SYSTEM OF MICROTUBULES, MICROFILAMENTS,
AND INTERMEDIATE FILAMENTS (ANIMAL ONLY)
•ALL ARE PROTEINS

MICROFILAMENTS
•THINNEST CYTOSKELETAL ELEMENTS (ROD-LIKE)
•COMPOSED OF THE GLOBULAR PROTEIN ACTIN
•ENABLE CELLS TO CHANGE SHAPE AND MOVE

•INTERMEDIATE FILAMENTS
•PRESENT ONLY IN ANIMAL CELLS OF CERTAIN
TISSUES
•FIBROUS PROTEINS JOIN TO FORM A ROPE-LIKE
STRUCTURE
•PROVIDE INTERNAL STRUCTURE
•ANCHOR ORGANELLES IN PLACE.

Protein filaments function in movement and support.
Figure 3-15

EM SCHWANN CELL INTERMEDIATE
FILAMENT &MICROTUBULE

CYTOSKELETON
•MICROTUBULES – LONG HOLLOW
TUBES MADE OF TUBULIN PROTEINS
(GLOBULAR)
•ANCHOR ORGANELLES AND ACT AS
TRACKS FOR ORGANELLE MOVEMENT
•MOVE CHROMOSOMES AROUND DURING
CELL DIVISION
•USED TO MAKE CILIA AND FLAGELLA

CELL JUNCTIONS
• PLASMA MEMBRANE PROTEINS CONNECT NEIGHBORING
CELLS - CALLED CELL JUNCTIONS
• 3 TYPES OF CELL JUNCTIONS IN ANIMAL CELLS
1. TIGHT JUNCTIONS
2. ANCHORING JUNCTIONS
3. GAP JUNCTIONS

CELL JUNCTIONS
1. TIGHT JUNCTIONS – MEMBRANE PROTEINS SEAL
NEIGHBORING CELLS SO THAT WATER SOLUBLE
SUBSTANCES CANNOT CROSS BETWEEN THEM
• SEEN BETWEEN STOMACH CELLS

CELL JUNCTIONS
2. ANCHORING JUNCTIONS – CYTOSKELETON FIBERS
JOIN CELLS IN TISSUES THAT NEED TO STRETCH
• SEE BETWEEN HEART, SKIN, AND MUSCLE CELLS
3. GAP JUNCTIONS – MEMBRANE PROTEINS ON
NEIGHBORING CELLS LINK TO FORM CHANNELS
• THIS LINKS THE CYTOPLASM OF ADJOINING CELLS

Gap junction
Anchoring
junction
Tight junction

CILIA AND FLAGELLA
o Hair-like projecting structures that move the cell by their movements
o Moves fluid, mucus, and materials over the cell surface
Example: Respiratory tract and female reproductive tracts
o Specialized arrangement of microtubules are responsible for their
locomotive ability

STRUCTURE
Cilia Similarities Flagella
 Short and numerous  Made of microtubules
(basal bodies)
 Hair-like
 Contain a core
(axoneme) consisting two
single central filaments
surrounded by an outer
ring of nine filaments
 Nine filaments are in
pairs and each join the
neighbouring filaments
 Enveloped in a
membrane that is an
extension of the plasma
membrane
 Long and usually
appears alone or in twos

CELL DIVISION
ALL CELLS ARE DERIVED
FROM PRE-EXISTING CELLS
NEW CELLS ARE PRODUCED
FOR GROWTH AND TO REPLACE
DAMAGED OR OLD CELL

KEEPING CELLS IDENTICAL
THE INSTRUCTIONS
FOR MAKING CELL
PARTS ARE ENCODED
IN THE DNA, SO
EACH NEW CELL
MUST GET A
COMPLETE SET OF
THE DNA
MOLECULES

DNA REPLICATION
DNA MUST BE
COPIED OR
REPLICATED BEFORE
CELL DIVISION
EACH NEW CELL
WILL THEN HAVE AN
IDENTICAL COPY OF
THE DNA
Original DNA
strand
Two new,
identical DNA
strands

IDENTICAL
DAUGHTER CELLS
84
Parent Cell
Two
identical
daughter
cells

COMPACTING DNA INTO
CHROMOSOMES
DNA IS
TIGHTLY
COILED
AROUND
PROTEINS
CALLED
HISTONES

CHROMOSOMES IN DIVIDING CELLS
DUPLICATED
CHROMOSOMES
ARE CALLED
CHROMATIDS &
ARE HELD
TOGETHER BY
THE
CENTROMERE
Called Sister Chromatids

KARYOTYPE
A PICTURE OF THE
CHROMOSOMES FROM A
HUMAN CELL ARRANGED IN
PAIRS BY SIZE
FIRST 22 PAIRS ARE
CALLED AUTOSOMES
LAST PAIR ARE THE SEX
CHROMOSOMES
XX FEMALE OR XY MALE
87

TYPES OF CELL REPRODUCTION
ASEXUAL REPRODUCTION
INVOLVES A SINGLE CELL
DIVIDING TO MAKE 2 NEW,
IDENTICAL DAUGHTER CELLS
MITOSIS & BINARY FISSION ARE
EXAMPLES OF ASEXUAL
REPRODUCTION
SEXUAL REPRODUCTION INVOLVES
TWO CELLS (EGG & SPERM)
JOINING TO MAKE A NEW CELL
(ZYGOTE) THAT IS NOT IDENTICAL
TO THE ORIGINAL CELLS
MEIOSIS IS AN EXAMPLE89

FIVE PHASES OF THE CELL CYCLE
G1 - PRIMARY GROWTH PHASE
S – SYNTHESIS; DNA REPLICATED
G2 - SECONDARY GROWTH PHASE
COLLECTIVELY THESE 3 STAGES
ARE CALLED INTERPHASE
M - MITOSIS
C - CYTOKINESIS
91

INTERPHASE - G1 STAGE
1ST GROWTH STAGE AFTER CELL
DIVISION
CELLS MATURE BY MAKING MORE
CYTOPLASM & ORGANELLES
CELL CARRIES ON ITS NORMAL
METABOLIC ACTIVITIES
93

INTERPHASE – S STAGE
SYNTHESIS STAGE
DNA IS COPIED OR REPLICATED
94
Two identical
copies of
DNA
Original DNA

INTERPHASE – G2 STAGE
2ND GROWTH STAGE
OCCURS AFTER DNA HAS BEEN COPIED
ALL CELL STRUCTURES NEEDED FOR
DIVISION ARE MADE (E.G. CENTRIOLES)
BOTH ORGANELLES & PROTEINS ARE
SYNTHESIZED
95

SKETCH THE CELL CYCLE
96
Daughter Cells
DNA Copied
Cells
Mature
Cells prepare for Division
Cell Divides into Identical cells

MITOSIS
DIVISION OF THE
NUCLEUS
ALSO CALLED
KARYOKINESIS
ONLY OCCURS IN
EUKARYOTES
HAS FOUR STAGES
DOESN’T OCCUR IN
SOME CELLS SUCH AS
BRAIN CELLS

FOUR MITOTIC STAGES
PROPHASE
METAPHASE
ANAPHASE
TELOPHASE

EARLY PROPHASE
CHROMATIN IN NUCLEUS CONDENSES TO
FORM VISIBLE CHROMOSOMES
MITOTIC SPINDLE FORMS FROM FIBERS IN
CYTOSKELETON OR CENTRIOLES (ANIMAL)
100
Chromosomes
Nucleolus Cytoplasm
Nuclear Membrane

LATE PROPHASE
NUCLEAR MEMBRANE & NUCLEOLUS ARE
BROKEN DOWN
CHROMOSOMES CONTINUE CONDENSING &
ARE CLEARLY VISIBLE
SPINDLE FIBERS CALLED KINETOCHORES
ATTACH TO THE CENTROMERE OF EACH
CHROMOSOME
SPINDLE FINISHES FORMING BETWEEN THE
POLES OF THE CELL 101

LATE PROPHASE
102
Nucleus & Nucleolus have disintegrated
Chromosomes

REVIEW OF PROPHASE
103
What the cell looks like
What’s happening

SPINDLE FIBERS
THE MITOTIC FORM FROM
CENTRIOLES IN ANIMAL CELLS
POLAR FIBERS EXTEND FROM ONE POLE
OF THE CELL TO THE OPPOSITE POLE
KINETOCHORE FIBERS EXTEND FROM
THE POLE TO THE CENTROMERE OF THE
CHROMOSOME TO WHICH THEY ATTACH
ASTERS ARE SHORT FIBERS RADIATING
FROM CENTRIOLES
104

METAPHASE
CHROMOSOMES, ATTACHED TO THE
KINETOCHORE FIBERS, MOVE TO THE CENTER
OF THE CELL
CHROMOSOMES ARE NOW LINED UP AT THE
EQUATOR
106
Pole of the
Cell
Equator of Cell

METAPHASE
107
Aster
Chromosomes at Equator

REVIEW OF METAPHASE
108
What the cell looks like
What’s occurring

ANAPHASE
OCCURS
RAPIDLY
SISTER
CHROMATIDS
ARE PULLED
APART TO
OPPOSITE POLES
OF THE CELL BY
KINETOCHORE
FIBERS

ANAPHASE REVIEW
110
What the cell
looks like
What’s
occurring

TELOPHASE
SISTER CHROMATIDS AT
OPPOSITE POLES
SPINDLE DISASSEMBLES
NUCLEAR ENVELOPE FORMS
AROUND EACH SET OF
SISTER CHROMATIDS
NUCLEOLUS REAPPEARS
CYTOKINESIS OCCURS
CHROMOSOMES REAPPEAR
AS CHROMATIN
111

COMPARISON OF ANAPHASE &
TELOPHASE
112

CYTOKINESIS
MEANS DIVISION OF THE
CYTOPLASM
DIVISION OF CELL INTO TWO,
IDENTICAL HALVES CALLED
DAUGHTER CELLS
IN ANIMAL CELLS, CLEAVAGE
FURROW FORMS TO SPLIT CELL113

CYTOKINESIS
114
Cleavage furrow in
animal cell

DAUGHTER CELLS OF MITOSIS
HAVE THE SAME NUMBER OF
CHROMOSOMES AS EACH OTHER
AND AS THE PARENT CELL FROM
WHICH THEY WERE FORMED
IDENTICAL TO EACH OTHER, BUT
SMALLER THAN PARENT CELL
MUST GROW IN SIZE TO BECOME
MATURE CELLS (G1 OF INTERPHASE)
116

IDENTICAL DAUGHTER CELLS
117
Chromosome number the same, but cells smaller
than parent cell
What is
the 2n or
diploid
number?
2

UNCONTROLLED MITOSIS
IF MITOSIS IS NOT
CONTROLLED,
UNLIMITED CELL
DIVISION OCCURS
CAUSING CANCEROUS
TUMORS
ONCOGENES ARE
SPECIAL PROTEINS
THAT INCREASE THE
CHANCE THAT A
NORMAL CELL DEVELOPS
INTO A TUMOR CELL 119
Cancer cells

MEIOSIS
FORMATION OF
GAMETES (EGGS &
SPERM)
120

FACTS ABOUT MEIOSIS
PRECEDED BY INTERPHASE WHICH INCLUDES
CHROMOSOME REPLICATION
TWO MEIOTIC DIVISIONS --- MEIOSIS I
AND MEIOSIS II
CALLED REDUCTION- DIVISION
ORIGINAL CELL IS DIPLOID (2N)
FOUR DAUGHTER CELLS PRODUCED THAT ARE
MONOPLOID (1N) 121

FACTS ABOUT MEIOSIS
DAUGHTER CELLS CONTAIN HALF THE
NUMBER OF CHROMOSOMES AS THE
ORIGINAL CELL
PRODUCES GAMETES (EGGS & SPERM)
OCCURS IN THE TESTES IN MALES
(SPERMATOGENESIS)
OCCURS IN THE OVARIES IN FEMALES
(OOGENESIS)
122

MORE MEIOSIS FACTS
123
 Start with 46 double stranded
chromosomes (2n)
After 1 division - 23 double stranded
chromosomes (n)
After 2nd division - 23 single stranded
chromosomes (n)
 Occurs in our germ cells that produce
gametes

WHY DO WE NEED MEIOSIS?
IT IS THE FUNDAMENTAL BASIS OF
SEXUAL REPRODUCTION
TWO HAPLOID (1N) GAMETES ARE
BROUGHT TOGETHER THROUGH
FERTILIZATION TO FORM A DIPLOID
(2N) ZYGOTE
124

REPLICATION OF CHROMOSOMES
REPLICATION IS THE
PROCESS OF DUPLICATING A
CHROMOSOME
OCCURS PRIOR TO
DIVISION
REPLICATED COPIES ARE
CALLED SISTER
CHROMATIDS
HELD TOGETHER AT
CENTROMERE
125
Occurs in
Interphase

MEIOSIS: TWO PART CELL
DIVISION
126
Homologs
separate
Sister
chromatids
separate
Diploid
Meiosis
I
Meiosis
II
Diploid
Haploid

MEIOSIS I: REDUCTION DIVISION
127
Nucleus Spindle
fibers
Nuclear
envelope
Early Prophase I
(Chromosome
number doubled)
Late Prophase
I
Metaphase I
Anaphase I Telophase I
(diploid)

PROPHASE I
128
Early prophase
Homologs pair.
Crossing over
occurs.
Late prophase
Chromosomes condense.
Spindle forms.
Nuclear envelope
fragments.

TETRADS FORM IN PROPHASE I
129
Homologous chromosomes
(each with sister chromatids)
Join to form a TETRAD
Called Synapsis

CROSSING-OVER
HOMOLOGOUS
CHROMOSOMES
IN A TETRAD
CROSS OVER EACH
OTHER
PIECES OF
CHROMOSOMES
OR GENES ARE
EXCHANGED
PRODUCES
GENETIC
RECOMBINATION
IN THE
OFFSPRING

HOMOLOGOUS CHROMOSOMES
DURING CROSSING-OVER
131

CROSSING-OVER
132
Crossing-over multiplies the already huge number
of different gamete types produced by
independent assortment

METAPHASE I
133
Homologous pairs of
chromosomes align
along the equator of
the cell

ANAPHASE I
134
Homologs separate and move
to opposite poles.
Sister chromatids remain
attached at their centromeres.

TELOPHASE I
135
Nuclear envelopes reassemble.
Spindle disappears.
Cytokinesis divides cell into
two.

MEIOSIS II: REDUCING
CHROMOSOME NUMBER
136
Prophase II
Metaphase II
Anaphase II
Telophase II
4 Identical
haploid cells

PROPHASE II
137
Nuclear envelope
fragments.
Spindle forms.

METAPHASE II
138
Chromosomes align
along equator of cell.

ANAPHASE II
139
Sister chromatids
separate and move to
opposite poles.
Equator
Pole

TELOPHASE II
140
Nuclear envelope
assembles.
Chromosomes
decondense.
Spindle disappears.
Cytokinesis divides cell
into two.

RESULTS OF MEIOSIS
141
Gametes (egg & sperm) form
Four haploid cells with one
copy of each chromosome
One allele of each gene
Different combinations of
alleles for different genes
along the chromosome

OOGENESIS
OR
SPERMATOGENESIS
142

SPERMATOGENESIS
OCCURS IN THE TESTES
TWO DIVISIONS PRODUCE 4
SPERMATIDS
SPERMATIDS MATURE INTO
SPERM
MEN PRODUCE ABOUT
250,000,000 SPERM PER DAY

OOGENESIS
OCCURS IN THE OVARIES
TWO DIVISIONS PRODUCE 3 POLAR
BODIES THAT DIE AND 1 EGG
POLAR BODIES DIE BECAUSE OF
UNEQUAL DIVISION OF CYTOPLASM
IMMATURE EGG CALLED OOCYTE
STARTING AT PUBERTY, ONE OOCYTE
MATURES INTO AN OVUM (EGG) EVERY
28 DAYS
145

OOGENESIS
146
Oogonium
(diploid)
Mitosis
Primary
oocyte
(diploid)
Meiosis I
Secondary
oocyte
(haploid)
Meiosis II
(if fertilization
occurs)
First polar body
may divide
(haploid)
Polar
bodies
die
Ovum (egg)
Second
polar body
(haploid)
a
A
X
X
a
X
A X
a
X
a
X
Mature
egg
A
X
A
X

24-
147
PATTERNS OF CHROMOSOME
INHERITANCE
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

24-
148
PRENATAL DETECTION OF
CONGENITAL DISEASE
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

24-
149
AMNIOCENTESIS
•AMNIOCENTESIS USES A NEEDLE TO EXTRACT AMNIOTIC FLUID
FROM THE UTERUS OF A PREGNANT WOMAN FROM THE 14TH TO
17TH WEEK OF PREGNANCY.
•UP TO 400 CHROMOSOME AND BIOCHEMICAL PROBLEMS CAN BE
DETECTED BY CULTURING FETAL CELLS THAT ARE IN THE AMNIOTIC
FLUID.
•THERE IS A SLIGHT RISK OF SPONTANEOUS ABORTION WITH THIS
PROCEDURE.

24-
151
CHORIONIC VILLI SAMPLING
•CHORIONIC VILLI SAMPLING (CVS) USES A THIN SUCTION
TUBE TO SAMPLE CHORIONIC CELLS FROM THE PLACENTA AS
EARLY AS THE FIFTH WEEK OF PREGNANCY.
•THE CELLS DO NOT HAVE TO BE CULTURED, AND KARYOTYPING
CAN BE DONE IMMEDIATELY.
•CVS CARRIES A SLIGHTLY GREATER RISK OF SPONTANEOUS
ABORTION BUT CAN BE PERFORMED EARLIER THAN
AMNIOCENTESIS.

24-
152
CHORIONIC VILLI SAMPLING

24-
153
VIEWING THE CHROMOSOMES
•A KARYOTYPE IS A DISPLAY OF CHROMOSOMES PAIRED
ACCORDING TO THEIR SIZE, LOCATION OF THE CENTROMERE,
AND STAINING PATTERNS.
•A KARYOTYPE REVEALS ABNORMALITIES IN CHROMOSOME
NUMBER OR STRUCTURE.
•HUMANS HAVE 23 PAIRS OF CHROMOSOMES; 22 PAIRS OF
AUTOSOMES AND ONE PAIR OF SEX CHROMOSOMES.
•FEMALES ARE XX AND MALES ARE XY.

Karyotype
The representation of entire metaphase chromosomes in a
cell, arranged in order of size and other characteristics

Ideogram
•Diagramatic representation
of a karyotype
•Individual chromsomes are
recognized by
-arm lengths
p, short
q, long
-centromere position
metacentric
sub-metacentric
acrocentric
telocentric
-staining (banding) patterns

•Q (QUINICRINE) & G (GIEMSA) BANDING PREFERENTIALLY STAIN AT
RICH REGIONS
•R (REVERSE BANDING) PREFERENTIALLY STAINS GC-RICH REGIONS
•C-BANDING (DENATURATION & STAINING) PREFERENTIALLY STAINS
CONSTITUTIVE HETEROCHROMATIN, FOUND IN THE CENTROMERE
REGIONS AND DISTAL YQ
Chromsome banding

Autosomal dominant disorders (neurofibromatosis, tuberous
sclerosis, polycystic kidney disease, familiar polyposis coli,
hereditary spherocytosis, Marfan syndrome, osteogenesis
imperfecta, achondroplasia, familiar hypercholesterolemia)
Autosomal recessive disorders (cystic fibrosis,
phenylketonuria, homocystinuria, hemochromatosis, sickle
cell anemia, thalassemias, alkaptonuria, neurogenic
muscular atrophies)
X-linked disorders (glucose-6-phosphate dehydrogenase
deficiency)

24-
161
SEX-LINKED TRAITS
•TRAITS CONTROLLED BY GENES ON THE X OR Y
CHROMOSOMES ARE SEX-LINKED ALTHOUGH MOST
ARE UNRELATED TO GENDER.
•AN ALLELE ON THE X CHROMOSOME THAT IS IN THE
REGION WHERE THE Y CHROMOSOME HAS NO
ALLELES WILL EXPRESS EVEN IF RECESSIVE; IT IS
TERMED X-LINKED.

24-
162
The presence of a Y chromosome determines maleness.
The SRY gene on the short arm of the Y produces a testis-
determining factor that begins the development of a male;
otherwise an embryo develops as a female.
Because the Y chromosome is so small, it has few genes that
are alleles of those on the X chromosome.
If a trait were recessive, a female would have to have two
recessive genes to express the trait; a male would only need
one.

24-
163
X-LINKED ALLELES
•THE KEY FOR AN X-LINKED PROBLEM SHOWS THE ALLELE
ATTACHED TO THE X AS IN:
• XB = NORMAL VISION
• XB = COLOR BLINDNESS.
•FEMALES WITH THE GENOTYPE XBXB ARE CARRIERS
BECAUSE THEY APPEAR TO BE NORMAL BUT EACH SON HAS
A 50% CHANCE OF BEING COLOR BLIND DEPENDING ON
WHICH ALLELE THE SON RECEIVES.
•XBXB AND XBY ARE BOTH COLORBLIND.

24-
164
CROSS INVOLVING AN X-LINKED ALLELE

24-
165
HEMOPHILIA
•HEMOPHILIA REFERS TO THE LACK OF ONE OF SEVERAL
CLOTTING FACTORS THAT LEADS TO EXCESSIVE BLEEDING IN
AFFECTED INDIVIDUALS.
•HEMOPHILIACS BLEED EXTERNALLY AFTER INJURY, BUT ALSO
BLEED INTERNALLY AROUND JOINTS.
•HEMORRHAGES CAN BE STOPPED WITH BLOOD
TRANSFUSIONS OR A BIOTECHNOLOGY CLOTTING FACTOR.

24-
166
MUSCULAR DYSTROPHY
•MUSCULAR DYSTROPHY IS CHARACTERIZED BY THE
WASTING OF MUSCLES.
•THE MOST COMMON FORM IS DUCHENNE MUSCULAR
DYSTROPHY; THIS IS AN X-LINKED DISORDER, OCCURRING
IN 1 OF 3,600 MALES.
•MUSCLES WEAKEN, FREQUENT FALLS AND DIFFICULTY IN
RISING OCCUR EARLY; DEATH OCCURS BY AGE 20.

24-
167
CHANGES IN CHROMOSOME NUMBER
• NONDISJUNCTION OCCURS DURING MEIOSIS I WHEN THE
MEMBERS OF A HOMOLOGOUS PAIR BOTH GO INTO THE SAME
DAUGHTER CELL OR DURING MEIOSIS II WHEN THE SISTER
CHROMATIDS FAIL TO SEPARATE AND BOTH DAUGHTER
CHROMOSOMES GO INTO THE SAME GAMETE.
•THE RESULT IS A TRISOMY OR A MONOSOMY.

24-
168
NONDISJUNCTION IN MEIOSIS I

24-
169
NONDISJUNCTION IN MEIOSIS II

24-
170
DOWN SYNDROME KARYOTYPE

24-
171
DOWN SYNDROME
•DOWN SYNDROME IS CAUSED BY TRISOMY 21, THREE COPIES OF
CHROMOSOME 21 AS A RESULT OF NONDISJUNCTION.
•SYMPTOMS INCLUDE MENTAL RETARDATION, SHORT STATURE,
EYELID FOLD, FLATTER FACE, A PALM CREASES, AND STUBBY
FINGERS, AMONG OTHERS.
•NONDISJUNCTION USUALLY OCCURRED IN PRODUCING THE
MOTHER’S EGG AND RISK INCREASES WITH THE WOMAN’S AGE.

24-
172
TURNER SYNDROME
•INDIVIDUALS WITH TURNER SYNDROME ARE FEMALES THAT HAVE
ONLY ONE X CHROMOSOME; THEREFORE THEY ARE XO.
•PHENOTYPES VARY BUT INDIVIDUALS MAY HAVE LATE ONSET OF
MENSTRUAL CYCLES AND MENSTRUAL FLOW MAY BE IRREGULAR. A
WEBBED-NECK IS OFTEN SEEN
•INTELLIGENCE CAN BE NORMAL; INDIVIDUALS ARE OFTEN
UNDIAGNOSED.

24-
173
KLINEFELTER SYNDROME
•INDIVIDUALS WITH KLINEFELTER SYNDROME ARE MALES THAT
ARE XXY.
•BREASTS MAY DEVELOP AND TESTES MAY BE REDUCED.
•KLINEFELTER MALES ARE USUALLY TALLER THAN AVERAGE AND
SLOW TO LEARN.

24-
174
CHANGES IN CHROMOSOME STRUCTURE
•RADIATION, ORGANIC CHEMICALS, OR EVEN VIRUSES MAY CAUSE
CHROMOSOMES TO BREAK, LEADING TO MUTATIONS.
•CHROMOSOMAL MUTATIONS INCLUDE INVERSION,
TRANSLOCATION, DELETION, AND DUPLICATION.

24-
175
•DELETIONS OCCUR WHEN A SINGLE BREAK CAUSES A LOST
END PIECE, OR TWO BREAKS RESULT IN A LOSS IN THE
INTERIOR.
•AN INDIVIDUAL WITH A NORMAL CHROMOSOME FROM ONE
PARENT AND A CHROMOSOME WITH A DELETION FROM THE
OTHER PARENT LACKS A PAIR OF ALLELES FOR SOME
TRAITS, AND A SYNDROME CAN RESULT.
•IN WILLIAMS SYNDROME, CHROMOSOME 7 LOSES AN END
PIECE AND CHILDREN HAVE A PIXIE LOOK AND THE SKIN
AGES PREMATURELY .

24-
177
•DUPLICATION RESULTS IN A CHROMOSOME SEGMENT
BEING REPEATED IN THE SAME CHROMOSOME OR IN A
NONHOMOLOGOUS CHROMOSOME, PRODUCING EXTRA
ALLELES FOR A TRAIT.
•AN INVERTED DUPLICATION IN CHROMOSOME 15 CAUSES
INV DUP 15 SYNDROME WITH POOR MUSCLE TONE,
MENTAL RETARDATION, AND RELATED SYMPTOMS.

24-
179
TRANSLOCATION
•TRANSLOCATION IS EXCHANGE OF CHROMOSOMAL SEGMENTS
BETWEEN TWO, NONHOMOLOGOUS CHROMOSOMES.
•IN A SMALL PERCENT OF CASES, A TRANSLOCATION BETWEEN
CHROMOSOMES 21 AND 14 CAUSES DOWN SYNDROME.
•THE TENDENCY FOR THIS PARTICULAR TRANSLOCATION CAN RUN
IN THE FAMILY OF EITHER THE MOTHER OR FATHER OF AFFECTED
INDIVIDUALS.

24-
181
INVERSION
•INVERSION INVOLVES A SEGMENT OF A CHROMOSOME
BEING TURNED 180 DEGREES; THE REVERSE SEQUENCE OF
ALLELES CAN ALTER GENE ACTIVITY.
•CROSSING-OVER BETWEEN INVERTED AND NORMAL
CHROMOSOMES CAN CAUSE RECOMBINANT
CHROMOSOMES DUE TO THE INVERTED CHROMOSOME
NEEDING TO FORM A LOOP TO ALIGN.

BIOCHEMICAL AND MOLECULAR BASIS OF
SINGLE-GENE DISORDERS
1) ENZYME DEFECTS AND THEIR CONSEQUENCES
2) DEFECTS IN RECEPTORS AND TRANSPORT SYSTEMS
3) ALTERATIONS IN STRUCTURE, FUNCTION OR QUANTITY OF
NONENZYME PROTEINS
4) GENETICALLY DETERMINED ADVERSE REACTIONS TO DRUGS.

DISORDERS ASSOCIATED WITH DEFECTS IN
STRUCTURAL PROTEINS
Marfan syndrome
A disorder of the connective tissues of the body, manifested principally by
changes in the skeleton, eyes, and cardiovascular system.
Ehlers-Danlos syndromes
A clinically and genetically heterogeneous group of disorders that result from
some defect in collagen synthesis or structure (other disorders resulting from
mutations affecting collagen synthesis include osteogenesis imperfecta, Alport
syndrome, epidermolysis bullosa)

RECEPTOR PROTEINS
Familiar hypercholesterolemia
A disease that is the consequence of a mutation in the
gene encoding the receptor for low-density lipoprotein
(LDL), which is involved in the transport and
metabolism cholesterol.

ENZYMES
Lysosomal storage diseases: . These disorders
result exclusively from mutations that lead to
reduced synthesis of lysosomal emzymes

ENZYMES
Tay-Sachs disease – GM2 gangliosidosis, hexosaminidase -subunit deficiency,GM2
ganglioside accumulates in heart, liver, spleen etc., destruction of neurons, proliferation
of microglia and accumulation of lipids in phagocytes within the brain.
Niemann-Pick disease – types A and B, two related disorders with lysosomal
accumulation of sphingomyelin, deficiency of sphingomyelinase, 80% of all cases
repreents type A – the severe infantile form with neurologic involvement, visceral
accumulation of sphingomyelin and early death within the first 3 years of life.
Gaucher disease – a cluster of autosomal recessive disorders resulting from mutations in
the gene encoding glucocerebrosidase, the most common lysosomal storage disorder,
accumulation of glucocerebrosides, types I-III, the glucocere¨brosides accumulate
within phygocytes (Gaucher cells) throughout the body – spleen, liver, bone marrow,
lymph nodes, tonsils thymus etc.

DISORDERS ASSOCIATED WITH
DEFECTS IN ENZYMES
Mucopolysaccharidoses (MPS) – the deficiencies of lysosomal enzymes involved in
the degradation of mucoplysaccharides (glycosaminoglycans), several clinical
variants classified from MPS I (Hurler syndrome) to MPS VII, each resulting from the
deficiency of one specific enzyme, all the MPS except one are autosomal recessive
disorders, the exception (Hynter syndrome) is an X-linked recessive disorder,
involvement of multiple organs including liver, spleen, heart, blood vessels, joint
stiffness, mental retardation.
Glycogen storage diseases – resulting from a hereditary deficiency of one of the
enzymes involved in the synthesis or sequential degradation of glycogen, 3 forms:
hepatic, myopathic, miscellaneous (deficiency of -glucosidase and lack of
branching enzymes, type II – Pompe disease and type IV, death early in life.

DEFECTS IN ENZYMES
Alkaptonuria (Ochronosis) – an autosomal recessive disorder in
which the lack of homogentisic oxidase blocks the metabolism
of phenylalanine-tyrosine at the level of homogentisic acid,
homogentisic acid accumulates in the body, it selectively binds
to collagen in connective tissues, tendons, and cartilage, these
tissues have a blue-black pigmentation (ochronosis) most
evident in the ears, nose, and cheeks, the deposits of the
pigment in the articular cartilages cause the cartilage to lose
its normal structure and function resulting in osteoarthritis.

PROTEINS THAT REGULATE CELL GROWTH
Neurofibromatosis: types 1 and 2 – two autosomal
dominant disorders, neurofibromatosis type 1
previously called von Recklinghausen disease,
neurofibromatosis type 2 previously called acoustic
neurofibromatosis. .

DEFECTS IN PROTEINS THAT REGULATE
CELL GROWTH
Neurofibromatosis-1: The neurofibromatosis 1 gene (NF-1) has
been mapped to chromosome 17q11.2. It encodes a protein
called neurofibromin, which down-regulates the function of
the p21ras oncoprotein. Three major features of disorder –
multiple neural tumors (neurofibromas) , numerous
pigmented skin lesions, and pigmented iris hamartomas, also
called Lisch nodules.

PROTEINS THAT REGULATE CELL GROWTH
Neurofibromatosis-2: an autosomal dominant disorder in
which patients develop a range of tumors – bilateral acoustic
schwannomas, multiple meningiomas, gliomas,
ependymomas of the spinal cord, ns –. The NF-2 gene, located
on chromosome 22q12

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