Topic 1: Specifying Identity

Question 1

Development of organism begins after _____
- Single celled zygote becomes multicellular by _____.

Answer 1

Fertilization; Mitosis

Question 2

Developing cells acquire different identities depending on their relative ____ within the embryo -> ______

Answer 2

Spatial Positions; Patterning

Question 3

Ensures that tissues and organs develop in the correct place and orientation

Answer 3

Pattern Formation

Question 4

Before pattern formation-

Answer 4

Cells become committed to develop into a certain part of the organism’s body.

Question 5

Four processes of Development:

Answer 5

Commitment
Differentiation
Morphogenesis
Growth

Question 6

Sets the fate of the cell

Answer 6

Commitment

Question 7

A process during which a cell ceases to divide and develops specialized structural elements and distinct functional properties

Answer 7

Differentiation

Question 8

Is the organization and spatial distribution of differentiated cells

Answer 8

Morphogenesis

Question 9

Is an increase in body size by cell division and cell expansion

Answer 9

Growth

Question 10

The oxford English dictionary defines commitment as an

Answer 10

“Engagement or involvement that restricts freedom of action.”

Question 11

During the course of commitment, what happens to the developmental fate?

Answer 11

Become restricted

Question 12

Many cells have a ____ before expressing any sign of differentiation.

Answer 12

State of commitment

Question 13

The process of commitment can be divided into 2 stages:

Answer 13

1. Specification
2. Determination

Question 14

A process of commitment in which the fate of a cell or a tissue is said to be specified when it is capable of differentiating autonomously when placed into a neutral environment (Petri dish or test tube)

Answer 14

Specification

Question 15

At the stage of specification, cell commitment is still ____, ____

Answer 15

labile; reversible

Question 16

Determination: A cell or tissue is said to be determined when it is capable of _____ even when placed into another region of the embryo or a cluster of differently specified cells.

The commitment is ____

Answer 16

differentiating atonomously
irreversible

Question 17

During embryogenesis, an undifferentiated cell matures through specific stages that cumulatively commit to a specific fate

Answer 17

1. Specification
2. Determination
3. Differentiation

Question 18

Modes of Specification
There are 3 general ways by which the commitment of cell can take place.

Answer 18

1. Autonomous Specification
2. Conditional Specification
3. Syncytial Specification

Question 19

Autonomous Specification:
The blastomeres of the early embryo are apportioned a set of critical _____ within the _____.

Answer 19

determination factors; egg cytoplasm

Question 20

Autonomous Specification:
_____________ are maternal substances in the egg that influence early development.

Answer 20

Cytoplasmic/ morphogenetic determinants

Question 21

Autonomous Specification:
An egg’s cytoplasm contains RNA, proteins and other substances that are distributed ___ in the unfertilized egg.

Answer 21

unevenly

Question 22

Autonomous Specification:
As the zygote divides by mitosis, cells contain different cytoplasmic determinants, which lead to _________

Answer 22

different gene expression

Question 23

The cell “knows” very early what it is to become without interacting with other cells
- Characteristic of most invertebrates

Answer 23

Autonomous specification

Question 24

Autonomous Specification:
Produces ______ development: cells cannot change fate if a blastomere is lost.

Answer 24

“mosaic” (“determinative”)

Question 25

Autonomous Specification:
_________ produce the same lineages in each embryo of the species. Blastomere fate are generally ______.

Answer 25

Invariant cleavages; invariant.

Question 26

Autonomous Specification:
The association of ____ with autonomous specification was confirmed by _______

Answer 26

Conklin’s fate map
Cell-removal experiments

Question 27

Autonomous Specification:
In 1973, ___ provide dramatic biochemical confirmation of the ______ of tissue determinants in early tunicate embryos

Answer 27

J. R Whittaker
cytoplasmic segragation

Question 28

The yellow-pigmented cytoplasm is mRNA for muscle-specific transcription factors called

Answer 28

Macho (give rise to muscle cells)

Question 29

Is the process by which cells achieve their respective fates by interacting with other cells.

Answer 29

Conditional specification

Question 30

Conditional specification:
Fate determined by various factors like:

Answer 30

• Cell-to-cell contacts
• Secreted signals
• Physical properties of local environment (mechanical stress)

Question 31

Paracrine vs. Juxtacrine

Answer 31

-

Question 32

This type of specification is a hybrid of autonomous and conditional that occurs in insects.

Answer 32

Syncytial specification

Question 33

A cytoplasm that contains many nuclei is called a _____ and the specification of presumptive cells within such syncytium is ______

Answer 33

Syncytium
Syncytial specification

Question 34

Syncytial specification method involves the action of ______ within the syncytium. As there are no cell boundaries in the syncytium, these morphogens can influence nuclei in ______.

Answer 34

morphogen gradients;
concentration-dependent manner.

Question 35

Syncytial specification: The insect egg cytoplasm is not ___

Answer 35

uniform

Question 36

_____ define position

Answer 36

Opposing axial gradients

Question 37

Each nucleus in Drosophila is given positional information whether that nucleus is to become part of the anterior, posterior, or midsection of the body) by _____

Answer 37

transcription factors acting as morphogens.

Question 38

The concentration of specific morphogens at any particular site tells the nuclei where they are

Answer 38

Relation to the source of the morphogenesis

Question 39

Morphogens involved in the Syncytial Specification of Drosophila Embryo:
The anterior-most portion (front) of the Drosophila embryo produces a morphogen called ____ with a concentration that is highest in the anterior and declines toward the posterior (anterior to posterior gradient).

Answer 39

Bicoid

Question 40

Morphogens involved in the Syncytial Specification of Drosophila Embryo:
The posteriormost portion of the egg forms a posterior to anterior (back to front) gradient of the morphogen ______

Answer 40

Caudal (and Nanos)

Question 41

Morphogens involved in the Syncytial Specification of Drosophila Embryo:
____ are both transcription factors, and different concentrations and ratios of Bicoid and Caudal (and Nanos) proteins activate different sets of genes in the syncytial nuclei.

Answer 41

Bicoid and Caudal