Cancer biology
Week 1
Preformationism = the belief that an organism’s development and growth were
predetermined only by its genetic material, wit hall structures and organs present in an
undeveloped form within the egg or sperm
Epigenesis = an organism’s development is shaped by the interaction of genes with
environmental factors, and that new structures and organs emerge gradually over the
course of development
Organisms have common genetic developmental plans
Development of the embryo goes through stages that
represents evolution of the ancesters
The tree of life → there is a common ancester, therefore we share DNA with other organisms
Several “model” organisms are used to study these “common developmental plans”
Model means “something that serves as a pattern” to understand how a biological process is
determined and orchestrated
Developmental biology as a discipline to study differentiation, growth and morphogenesis
- Organisms do not spring forth fully formed
- Development begins with a single cell → fertilized egg, or zygote (fully undifferentiated cell)
- The zygote divides mitotically to produce even more specialized cells of the sculpted
organism (differentiation)
- They arise by a relatively slow process of progressive change (growth and morphogenesis) →
development
Undifferentiated cell has the potential to develop into any cell of the organism
Cell differentiation = process by which a single cell becomes a specialized cell type with specific
functions in the body (muscle cells, nerve cells and blood cells) eacht with its own unique
characteristics and functions
Morphogenesis = the creation of a high ordered organism
,An animal’s life cycle: embryogenesis
Embryogenesis = process of
development of an embryo
from fertilization of the egg by
sperm until it becomes a
mature organism
1. Fertilization: process of the male + female gamets (sperm + egg) to a zygote, the 1st cell of a
new organism. It marks the beginning of embryonic development
2. Cleavage: process of cell division that occurs during the early stages of embryonic
development, where the zygote (single cell) divides into multiple smaller cells (blastomeres)
without increasing in size. This process forms the morula (solid ball of cells), which eventually
develops into a blastocyst (a fluid-filled structure that implants into the uterus and forms the
placenta)
3. Gastrulation: development process that occurs in the early stage of embryonic development
in animals. It results in the formation of 3 germ layers (ecto-, meso-, endoderm), which will
give rise to different parts of the body. This process is crucial for the formation of the basic
body plan
4. Organogenesis: process of forming/developing organs in a developing organism. It occurs
during embryonic development and involves the formation of specific tissues and the
differentiation of cells into specific cell types, leading tot he formation of ucntional organs
,Mitosis and meiosis
Mitosis and meiosis are two different cell division processes that
differ in their purpose and mechanism:
1. Purpose: mitosis is used for asexual reproduction, cell
growth and tissue repair.
Meiosis is used for sexual repoduction
2. Number of daughter cells: mitosis produces two identical
daughter cells with the same number of chromosomes as
the parent cell.
Meisosis produces 4 non-identical
daughter cells with half number of
chromosomes as the parent cell
3. Chromosome distribution: mitosis chromosomes are distributed equally to daughter cells.
Meiosis chromosomes are distributed randomly to daughter cells,
leading genetic diversity → mendel’s law of independent segregation
4. Stages: mitosis: prophase, metaphase, anaphase and telophase
Meiosis: prohase (I, II), metaphase (I, II), anaphase (I, II), Telophase (I, II), cytokinesis
(I, II)
Meiosis: formation of haploid cells
Oogenesis Spermatogenesis
Mammals
Stop cell cycle → continue when fertilization
Fertilization: diploidy and restauration of the cell cycle
, Calcium = red → spreading in egg after fertilization
➔ This is the restart of cell cycle + blocks the entry of other sperm cells
(poly spermcells)
Fertilization: symmetry breakage
In C. elegans, the entry of
sperm during fertilization determines the axis of
asymmetry in the developing embryo. This process
is called "symmetry breaking."
The sperm entry point determines which end of the
zygote will become the head and which will become
the tail → crucial process for the proper
development of the organism + the establishment
of its anterior-posterior asymmetry.
After the first cell division: anterior cell (AB) is
always bigger and will always give rise to its
daughter cells (Aba and Abp), while the posterior
cell is always smaller and give rise to other daughter
cells (EMS and P2).
The rising of two non-identical cells after cell division is the consequence of an
asymmetric cell division, which usually occur in stem cells
Cleavage: patterns diverge for different organisms
Hoboblastic cleavage = the division of the entire egg
into smaller cells, resulting in a group of cells →
blastula
Meroblastic cleavage = partial division of the egg, resulting in a smaller mass of cells
attached to the yolk
Week 1
Preformationism = the belief that an organism’s development and growth were
predetermined only by its genetic material, wit hall structures and organs present in an
undeveloped form within the egg or sperm
Epigenesis = an organism’s development is shaped by the interaction of genes with
environmental factors, and that new structures and organs emerge gradually over the
course of development
Organisms have common genetic developmental plans
Development of the embryo goes through stages that
represents evolution of the ancesters
The tree of life → there is a common ancester, therefore we share DNA with other organisms
Several “model” organisms are used to study these “common developmental plans”
Model means “something that serves as a pattern” to understand how a biological process is
determined and orchestrated
Developmental biology as a discipline to study differentiation, growth and morphogenesis
- Organisms do not spring forth fully formed
- Development begins with a single cell → fertilized egg, or zygote (fully undifferentiated cell)
- The zygote divides mitotically to produce even more specialized cells of the sculpted
organism (differentiation)
- They arise by a relatively slow process of progressive change (growth and morphogenesis) →
development
Undifferentiated cell has the potential to develop into any cell of the organism
Cell differentiation = process by which a single cell becomes a specialized cell type with specific
functions in the body (muscle cells, nerve cells and blood cells) eacht with its own unique
characteristics and functions
Morphogenesis = the creation of a high ordered organism
,An animal’s life cycle: embryogenesis
Embryogenesis = process of
development of an embryo
from fertilization of the egg by
sperm until it becomes a
mature organism
1. Fertilization: process of the male + female gamets (sperm + egg) to a zygote, the 1st cell of a
new organism. It marks the beginning of embryonic development
2. Cleavage: process of cell division that occurs during the early stages of embryonic
development, where the zygote (single cell) divides into multiple smaller cells (blastomeres)
without increasing in size. This process forms the morula (solid ball of cells), which eventually
develops into a blastocyst (a fluid-filled structure that implants into the uterus and forms the
placenta)
3. Gastrulation: development process that occurs in the early stage of embryonic development
in animals. It results in the formation of 3 germ layers (ecto-, meso-, endoderm), which will
give rise to different parts of the body. This process is crucial for the formation of the basic
body plan
4. Organogenesis: process of forming/developing organs in a developing organism. It occurs
during embryonic development and involves the formation of specific tissues and the
differentiation of cells into specific cell types, leading tot he formation of ucntional organs
,Mitosis and meiosis
Mitosis and meiosis are two different cell division processes that
differ in their purpose and mechanism:
1. Purpose: mitosis is used for asexual reproduction, cell
growth and tissue repair.
Meiosis is used for sexual repoduction
2. Number of daughter cells: mitosis produces two identical
daughter cells with the same number of chromosomes as
the parent cell.
Meisosis produces 4 non-identical
daughter cells with half number of
chromosomes as the parent cell
3. Chromosome distribution: mitosis chromosomes are distributed equally to daughter cells.
Meiosis chromosomes are distributed randomly to daughter cells,
leading genetic diversity → mendel’s law of independent segregation
4. Stages: mitosis: prophase, metaphase, anaphase and telophase
Meiosis: prohase (I, II), metaphase (I, II), anaphase (I, II), Telophase (I, II), cytokinesis
(I, II)
Meiosis: formation of haploid cells
Oogenesis Spermatogenesis
Mammals
Stop cell cycle → continue when fertilization
Fertilization: diploidy and restauration of the cell cycle
, Calcium = red → spreading in egg after fertilization
➔ This is the restart of cell cycle + blocks the entry of other sperm cells
(poly spermcells)
Fertilization: symmetry breakage
In C. elegans, the entry of
sperm during fertilization determines the axis of
asymmetry in the developing embryo. This process
is called "symmetry breaking."
The sperm entry point determines which end of the
zygote will become the head and which will become
the tail → crucial process for the proper
development of the organism + the establishment
of its anterior-posterior asymmetry.
After the first cell division: anterior cell (AB) is
always bigger and will always give rise to its
daughter cells (Aba and Abp), while the posterior
cell is always smaller and give rise to other daughter
cells (EMS and P2).
The rising of two non-identical cells after cell division is the consequence of an
asymmetric cell division, which usually occur in stem cells
Cleavage: patterns diverge for different organisms
Hoboblastic cleavage = the division of the entire egg
into smaller cells, resulting in a group of cells →
blastula
Meroblastic cleavage = partial division of the egg, resulting in a smaller mass of cells
attached to the yolk
