27. Factors and mechanisms of morphogenesis. Genetic basis of embryogenesis.

Question 1

Preformationism (preformism) - the idea that organisms develop from miniature versions of themselves

Answer 1

Preformationism (preformism) - the idea that organisms develop from miniature versions of themselves

Question 2

Epigenesis

• the denial of preformationism
• each embryo or organism is gradually produced from an undifferentiated mass by a series of steps and stages during which new parts are needed
• contemporary opinion: the development is the result of genetic grounds that are realised under the influence of external factors

Answer 2

Epigenesis

• the denial of preformationism
• each embryo or organism is gradually produced from an undifferentiated mass by a series of steps and stages during which new parts are needed
• contemporary opinion: the development is the result of genetic grounds that are realised under the influence of external factors

Question 3

Factors of embryogenesis:

• polarity of the egg (epigenetic factors) - polarity is material but formed by random factors in ovarium
• how bilateral symmetry was formed
• role of point of penetration of sperm
• direction and role of I, II and III cleavage
• left, right, top, down + front - rear direction
• Internal - relating to the nucleus and its genetic material
• External - related to the cytoplasm and environment - epigenetic. e.g. polarity of the egg or the point of penetration of the sperm according to which the first 3 divisions takes place, may be influencing development of the embryo

Answer 3

Factors of embryogenesis:

• polarity of the egg (epigenetic factors) - polarity is material but formed by random factors in ovarium
• how bilateral symmetry was formed
• role of point of penetration of sperm
• direction and role of I, II and III cleavage
• left, right, top, down + front - rear direction
• Internal - relating to the nucleus and its genetic material
• External - related to the cytoplasm and environment - epigenetic. e.g. polarity of the egg or the point of penetration of the sperm according to which the first 3 divisions takes place, may be influencing development of the embryo

Question 4

Preformationists believe that the form of living things exist in real terms, prior to their development. Preformationism suggests that all organisms were created at the same time.

Answer 4

Preformationists believe that the form of living things exist in real terms, prior to their development. Preformationism suggests that all organisms were created at the same time.

Question 5

Differentiation:

It’s the process by which in mature cells or tissues develop into mature cells or tissues. It’s accompanied by specific protein expression and cytoskeleton modifications

Answer 5

Differentiation:

It’s the process by which in mature cells or tissues develop into mature cells or tissues. It’s accompanied by specific protein expression and cytoskeleton modifications

Question 6

Determination:

It’s the process that occurs as cells undergo development and their destiny becomes progressively more restricted. They continue to differentiate until only a single pathway of differentiation is chosen.

Answer 6

Determination:

It’s the process that occurs as cells undergo development and their destiny becomes progressively more restricted. They continue to differentiate until only a single pathway of differentiation is chosen.

Question 7

Induction:

It’s the process by which a chemical mediator released from the embryo causes a specific morphogenetic effect in another part by inducing a particular development pathway. e.g. the dermis of the skin, derived from the mesoderm, releases a substance that causes the overlying ectoderm to differentiate into epidermis

Answer 7

Induction:

It’s the process by which a chemical mediator released from the embryo causes a specific morphogenetic effect in another part by inducing a particular development pathway. e.g. the dermis of the skin, derived from the mesoderm, releases a substance that causes the overlying ectoderm to differentiate into epidermis

Question 8

Morphogenesis:

• process causing an organism to develop its shape
• morphogenesis controls organised spatial distribution of cells during embryonic period of organism
• animal morphogenesis is accomplished by growth + cell movement. A fixed pattern is predetermined early during gastrulation - once organs + formed, no new ones with exceptions are formed

Answer 8

Morphogenesis:

• process causing an organism to develop its shape
• morphogenesis controls organised spatial distribution of cells during embryonic period of organism
• animal morphogenesis is accomplished by growth + cell movement. A fixed pattern is predetermined early during gastrulation - once organs + formed, no new ones with exceptions are formed