Transcript Chapter 2 - TeacherWeb

Human Genetics
Concepts and Applications
Tenth Edition
RICKI LEWIS
2
Cells
PowerPoint® Lecture Outlines
Prepared by Johnny El-Rady, University of South Florida
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Introducing Cells
Cellular activities and abnormalities underlie
our inherited traits, quirks, and illnesses
Understanding genetic diseases can
suggest ways to treat the condition
Figure 2.1
Lack of
dystrophin
2
Introducing Cells
Our bodies include more than 260 cell types
Somatic (body) cells have two copies of
the genome and are said to be diploid
Sperm and egg cells have one copy of the
genome and are haploid
Stem cells can both replicate themselves
and give rise to differentiated cells
3
Types of Cells
All cells can be divided into two main types
Prokaryotic cells
- Lack a nucleus
Eukaryotic cells
- Possess a nucleus
and other organelles
Figure 2.2
4
Domains of Life
Biologists recognize three broad categories
of organisms
Archaea – Unicellular prokaryotes
Bacteria – Unicellular prokaryotes
Eukarya – Includes both unicellular and
multicellular eukaryotes
5
Chemical Constituents
Cells contain four types of macromolecules
Type
Examples
Functions
Carbohydrates Sugars, starches Energy,
structure
Lipids
Fats, oils
Membranes,
hormones
Proteins
Myosin, collagen Enzymes,
structure
Nucleic Acids DNA, RNA
Genetic
information
6
An Animal Cell
Surrounded by the plasma membrane
Contains:
- Cytoplasm
- Organelles
- Divide labor by partitioning certain
areas or serving specific functions
Figure 2.3
7
An Animal Cell
Figure 2.3
Figure 2.3
8
The Nucleus
The largest structure in a cell
Surrounded by a double-layered nuclear
envelope
Contains:
- Nuclear pores that allow movement of some
molecules in and out
- Nucleolus, which is the site of ribosome
production
- Chromosomes composed of DNA and
Figure 2.3
proteins
9
The Nucleus
Figure 2.4
Figure 2.3
Figure 2.4
10
Secretion
illustrates
how
organelles
function
together
to
coordinate
the basic
functions
of life
Figure 2.5
11
Endoplasmic Reticulum (ER)
Interconnected membranous tubules & sacs
Winds from the nuclear envelope to the
plasma membrane
Rough ER contains ribosomes and is
involved in protein synthesis
Smooth ER does not contain ribosomes
and is important in lipid synthesis
Figure 2.3
12
Golgi Apparatus
Stack of flat membrane-enclosed sacs
Processing center that adds sugars forming
glycoproteins and glycolipids
Site of final protein folding
Products are released into vesicles that bud
off to the plasma membrane
Figure 2.3
13
Lysosomes
Membrane-bound sacs
containing > 40 types
of digestive enzymes
Break down bacteria,
cellular debris, and
nutrients
Tay-Sachs is an
inherited lysosomal
Figure 2.6
storage disorder Figure 2.3
14
Peroxisomes
Sacs with outer membranes studded with
several types of enzymes
Break down lipids, rare biochemicals
Synthesize bile acids
Detoxify compounds from free radicals
Abundant in liver and kidney cells
Figure 2.3
15
Mitochondria
Surrounded by two
membranes
Site of ATP (energy)
production
Contain their own
circular DNA
Figure 2.7
Human mitochondrial
DNA is inherited
only from the mother
Figure 2.3
16
Structures and Functions of
Organelles
Table 2.1
17
Plasma Membrane
Forms a selective
barrier
A phospholipid
bilayer
- Phosphate end
(hydrophilic)
- Fatty acid chains
(hydrophobic)
Figure 2.8
Figure 2.3
18
Plasma Membrane
Contains proteins,
glycoproteins,
and glycolipids
- Important to cell
function and
interactions
- May be receptors
- Form channels for
ions
FigureFigure
2.3 2.9
19
Faulty Ion Channels Cause
Inherited Diseases
Sodium channels
- Mutations lead to absence or extreme pain
Potassium channels
- Mutations lead to impaired heart function and
deafness
Chloride channels
- Mutations leadFigure
to cystic
2.3 fibrosis
20
Cytoskeleton
A meshwork of
protein rods and
tubules
Includes three major
types of proteins
- Microtubules
- Microfilaments
- Intermediate
filaments
Figure 2.3
Figure 2.10
21
Cytoskeleton Functions
Maintain cell shape
Connect cells to each other
Transport organelles and small molecules
Provide cell motility (some cell types)
Move chromosomes in cell division
Compose cilia Figure 2.3
22
Figure 2.11
23
Figure 2.12
24
Cell Division and Death
Normal growth and development require an
intricate interplay between the rates of two
processes
Mitosis – Cell division
- Produces two somatic cells from one
Apoptosis – Cell death
- Precise genetically-programmed sequence
Figure 2.3
25
Figure 2.13
Figure 2.12
26
The Cell Cycle
The sequence of events associated with cell division
G phase: Gap for
growth
S phase: DNA
synthesis
M phase: Mitosis
(nuclear division)
Cytokinesis: Cell
division
Figure 2.14
Figure 2.3
27
Stages of the Cell Cycle
Interphase
- Prepares for cell division
- Replicates DNA and subcellular structures
- Composed of G1, S, and G2
- Cells may exit the cell cycle at G1 or enter G0,
a quiescent phase
Mitosis – Division of the nucleus
Cytokinesis – Division
of
the
cytoplasm
Figure 2.3
28
Replication of Chromosomes
Chromosomes are
replicated during
S phase prior to
mitosis
Figure 2.15
The result is two
sister chromatids
held together at
the centromere
Figure 2.3
29
Mitosis
Used for growth, repair, and replacement
Consists of a single division that produces
two identical daughter cells
A continuous process divided into 4 phases
- Prophase
- Metaphase
- Anaphase
- Telophase
Figure 2.3
30
Mitosis in a Human Cell
Figure 2.15
Figure 2.16
31
Prophase
Replicated
chromosomes
condense
Microtubules
organize into a
spindle
Nuclear envelope
and nucleolus
break down
Figure
Figure2.3
2.16
32
Metaphase
Chromosomes line
up on the cell’s
equator
Spindle microtubules
are attached to
centromeres of
chromosomes
Figure
Figure2.3
2.16
33
Anaphase
Centromeres divide
Chromatids separate and
become independent
chromosomes
- They move to opposite
ends of the cell
Figure
Figure2.3
2.16
34
Telophase
Chromosomes uncoil
Spindle disassembles
Nuclear envelope
reforms
Figure
Figure2.3
2.16
35
Cytokinesis
Cytoplasmic division occurs after nuclear
division is complete
Organelles and macromolecules are
distributed between the two daughter cells
Microfilament band contracts, separating
the two cells
Figure 2.3
36
Cell Cycle Control
Checkpoints ensure that mitotic events
occur in the correct sequence
Internal and external factors are involved
Many types of cancer result from faulty
checkpoints
Figure 2.3
37
Cell Cycle Control
Figure 2.17
Figure 2.16
38
Telomeres
Located at the ends of the chromosomes
Contain hundreds to thousands of repeats
of a 6-base DNA sequence
Most cells lose 50-200 endmost bases after
each cell division
After about 50 divisions, shortened
telomeres signal the cell to stop dividing
Sperm, eggs, bone marrow, and cancer
cells produce telomerase that prevent
Figure 2.3
shortening of telomeres
39
Figure 2.18
40
Apoptosis
Begins when a cell receives a “death signal”
Killer enzymes called caspases are
activated
-Destroy cellular components
Phagocytes digest the remains
Dying cell forms bulges called blebs
Figure 2.3
41
Programmed cell death is part of normal development
Figure 2.19
Mitosis and apotosis work
together to form functional body
Cancer can result from too much
mitosis, too little apotosis
Figure 2.18
42
Cell-to-Cell Interactions
Make multicellular life possible
Two broad types
1) Signal transduction
2) Cellular adhesion
Defects cause certain inherited disorders
Figure 2.3
43
Signal Transduction
The process of transmitting a signal from
the environment to a cell
- Receptor binds to “first messenger”
- Interacts with regulator
- Causes enzyme to produce “second
messenger”
- Elicits cellular response, which is
typically enzyme activation
- AmplificationFigure
due 2.3
to cascade
44
Signal Transduction
Figure 2.20
Figure 2.19
45
Cellular Adhesion
A precise sequence of interactions among
proteins that connect cells
Example = Inflammation
- Three types of cellular adhesion
molecules (CAMs) help guide WBCs to
the injured area
- Secretins, integrins, and adhesion
receptor proteins
Figure 2.3
46
Cellular Adhesion
Figure 2.21
Figure 2.20
47
Stem Cells
A stem cell divides by
mitosis
- Produces daughter
cells that retain the
ability to divide and
some that specialize
Progenitor cells do
not have the capacity
of self-renewal
Figure 2.3Figure 2.22
48
Stem Cells
All cells in the human body descend from
stem cells via mitosis and differentiation
Cells differentiate down cell lineages by
differential gene expression
Stem cells are present throughout life and
provide growth and repair
Figure 2.3
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Figure 2.23
Figure 2.3
50
Stem Cells
Stem cells and progenitor cells are described
in terms of their developmental potential
Totipotent – Can give rise to every cell type
Pluripotent – Have fewer possible fates
Multipotent – Have only a few fates
Figure 2.3
51
Stem Cells in Health Care
There are 3 general sources of human stem cells
1) Embryonic stem cells – Created in a lab dish
using the inner cell mass (ICM) of an embryo
2) Induced pluripotent stem (iPS) cells –
Somatic cells reprogrammed to differentiate into
any of several cell types
3) Adult stem cells – Tissue-specific or somatic
stem cells
Figure 2.3
52
Stem Cells in Health Care
Figure 2.24
Figure 2.24
53
Stem Cell Applications
Stem cells are being used in four basic ways
1) Discovery and development of drugs
2) Observing the earliest sign of disease
3) Treatment of disease via implants and
transplants
4) Stimulating stem cells in the body via the
introduction of reprogramming
proteins
Figure 2.3
54
Stem Cell Applications
Figure 2.25
Figure 2.3
55