Development of Multicellular Organisms I

Question 1

How do cells have memory?

Answer 1

Retain record of signals their ancestors received during embryonic development.
Remember the environment

Question 2

Homologous proteins are functionally _________.

Answer 2

Interchangeable

Question 3

What constitutes the ectoderm?

Answer 3

Cells that cohere to form a sheet of epithelial cells facing external medium

Question 4

Ectoderm is a precursor of what?

Answer 4

precursor of nervous system and epidermis

Question 5

What constitutes the endoderm?

Answer 5

Part of the epithelial sheet becomes tucked into the interior

Question 6

What is the endoderm a precursor of?

Answer 6

Gut, lung, and liver

Question 7

What forms the mesoderm?

Answer 7

Group of cells move into the space between ectoderm and endoderm and form the mesoderm

Question 8

What is the mesoderm a precursor of?

Answer 8

Muscles and connective tissue

Question 9

What is gastrulation?

Answer 9

Transformation of a hollow sphere of cells into a structure with gut

Question 10

Higher organisms have several homologs of the same gene called what?

Answer 10

gene duplication

Question 11

What are two classes of proteins most important for development?

Answer 11

Cell adhesion and cell signaling proteins

Gene regulatory proteins

Question 12

Where are instructions for producing a multicellular animal contained in?

Answer 12

In the non-coding regulatory DNA associated with each gene

Question 13

DNA contains regulatory elements that serve as binding sites for what/

Answer 13

gene regulatory proteins

Question 14

What defines the sequential program for development?

Answer 14

Regulatory DNA

Question 15

Coding sequences in DNA are similar in most organisms but non-coding sequences make one organism what?

Answer 15

different from one another and provide uniqueness

Question 16

Cell that are fated to develop into a specialized cell type despite changes in environment are called what?

Answer 16

Determined

cells make developmental decisions long before they show any outward signs of differentiation

Question 17

Cells that can change rapidly due to alterations in environment are called what?

Answer 17

Completely undetermined

Question 18

Cells that have some attributes of a particular cell type but can change with environment are called what?

Answer 18

Committed

Question 19

Before acquiring a particular fate, cells express genes that are markers of their location, they are ______.

Answer 19

regionally determined

Question 20

What is a position specific character of a cell called?

Answer 20

positional value

Question 21

Cell can become different due to ________ division. These are significant sets of molecules distributed unequally between daughter cells

Answer 21

asymmetric

Question 22

How can cells born the same can become different?

Answer 22

Due to change in environment after birth

*these molecules then directly or indirectly alter pattern of gene expression between the 2 cells

Question 23

What are the most important environmental cues to a developing cell?

Answer 23

Signals from neighboring cells

Question 24

Whats the term?

Induction of a different developmental program in select cells in a homogeneous group leading to altered character

Answer 24

inductive signaling

*few cells closest to the source take on induced character-signal is limited in time and space

Question 25

What are the types of signal ranges?

Answer 25

Short range: cell-cell contact

Long range: substances that can diffuse through the extracellular medium

Question 26

How do systems start off?

Answer 26

homogenous and symmetrical

Question 27

What does the environment impose on the symmetry?

Answer 27

Weak asymmetry

Question 28

How is asymmetry amplified?

Answer 28

positive feedback

*provides cells with memory

Question 29

Broken asymmetry is what type of phenomenon?

Answer 29

“all or none”

Question 30

Morphogen

Answer 30

a long range inductive signal that imposes a pattern on a field of cells. exert graded effects by forming gradients of different concentrations

Question 31

Each concentration can direct the target cells into a different _________.

Answer 31

developmental pathway

Question 32

How is the gradient formed?

Answer 32

By localized production of an inducer that diffuses away from its source
Localized production of an inhibitory that diffuses away from its source and block the action of a uniformly distributed inducer

Question 33

What do morphogens need?

Answer 33

an ‘on’ and ‘off’ system

Question 34

How are interactions of morphogens blocked?

Answer 34

antagonists or extracellular inhibitors bind to the signal or its receptor

Question 35

Describe general characteristics of signaling pathways

Answer 35

Conserved family of proteins
Ultimate result of inductive events is change in DNA transcription
Some genes turned ‘on’ others ‘off’
Response depends on spatial and temporal expression of different sets of genes