Lecture 30: General Principles Of Development

Question 1

What are the 2 underlying principles of development?

Answer 1

Cell division

Cell differentiation

Question 2

Since the genome of all cells in an organism is identical, what is the primary controller of development?

Answer 2

Gene expression

Question 3

What are the 4 cellular processes occurring throughout the development of an embryo?

Answer 3

Cell proliferation

Cell specialization

Cell interaction

Cell movement

Question 4

What is the significance of the statement: “cells have memory”

Answer 4

Cells retain a record of signals their ancestors received during embryonic development, so current gene expression is a reflection of past AND present environment

Question 5

T/F Homologous proteins are functionally interchangeable

Answer 5

True

Mouse Engrailed-1 protein has homologous protein in Drosophila called Engrailed. Can be transplanted and works the same

Question 6

What germ layer forms the precursor of gut, lung, and liver?

Answer 6

Endoderm

Question 7

What germ layer forms the precursor of nervous system and epidermis?

Answer 7

Ectoderm

Question 8

What germ layer forms the precursor of muscles and connective tissue?

Answer 8

Mesoderm

Question 9

The transformation of a hollow sphere of cells into a structure with a gut is called ______________

Answer 9

Gastrulation

Question 10

Describe the ectoderm

Answer 10

Sheet of epithelial cells facing the external medium

Question 11

Describe endoderm

Answer 11

Formed when of epithelial sheet becomes tucked into interior

Question 12

Describe mesoderm

Answer 12

Formed when the group of cells move into the space between ectoderm and endoderm

Question 13

Compare coding with non-coding regions of DNA

Answer 13

Coding - similar in most organisms

Non-coding - provide uniqueness, contain gene regulatory proteins to control expression

Question 14

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

Cells that are fated to develop into a specialized cell type despite changes in environment are called ________________

Answer 14

Determined

Question 15

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

Cells that can change rapidly due to alterations in the environment are called _______________

Answer 15

Completely undetermined

Question 16

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

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

Answer 16

Committed

Question 17

What is the significance of cellular memory of positional values?

Answer 17

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

Cells retain memory of this value –> they are regionally determined

Question 18

Cells can become different due to what type of division: symmetric or asymmetric?

Answer 18

Asymmetric - significant sets of molecules are distributed unequally between daughter cells

Question 19

How do sister cells become different when they symmetrically divide?

Answer 19

Environmental influences alter gene expression

Question 20

Where do most important environmental cues come from with inductive signaling?

Answer 20

Neighboring cells

Question 21

_____________ ____________ defines the process by which induction of a different developmental program in select cells in a homogenous group leading to altered character

Answer 21

Inductive signaling

Question 22

What are the 2 types of inductive signaling?

Answer 22

Short range - cell-cell contacts

Long range - substances diffuse through EC medium

Question 23

A ____________ is a long-range inductive signal that imposes a pattern on a field of cells

Answer 23

Morphogen

Question 24

What is unique about morphogen signaling?

Answer 24

It exerts graded effects by forming gradients of different concentrations

Question 25

What are the two components of a morphogen-induced gradient?

Answer 25

Localized production of INDUCER that diffuses away from its source

Localized production of INHIBITOR that diffuses away from its source and blocks action of uniformly distributed inducer

Question 26

What are the 2 variable components to generating a signal gradient?

Answer 26

Speed of diffusion

Half-life of morphogen

Question 27

A system starts of homogeneous and symmetrical. The environment imposes a weak asymmetry. What process amplifies this effect?

Answer 27

Positive feedback

Question 28

True or false: positive feedback mechanisms are reversible with the right external signaling

Answer 28

False: PF is irreversible. Once achieved, external signaling becomes irrelevant

Question 29

What is the ligand and what is the receptor in Delta Notch signaling?

Answer 29

Delta is a signal TM protein = ligand

Notch = receptor

Question 30

What two processes are demonstrated by delta notch signaling?

Answer 30

Lateral inhibition and positive feedback

Question 31

Describe delta notch signaling

Answer 31

When two cells are engaged, part of the notch undergoes proteolysis. A small fragment of the receptor (notch) migrates to the nucleus and initiates gene transcription.

The more active that delta is of one cell, the less active the delta is of the other cell

Question 32

What are the 3 main factors contributing to diversity in patterns?

Answer 32

Gene duplication

Presence of other signals

Previous experiences of the cell

Question 33

Signaling pathways originate from a handful of conserved proteins. What is the ultimate result of inductive events?

Answer 33

A change in DNA transcription

Question 34

Response in signaling pathways depends on __________ and ___________ expression of different sets of genes

Answer 34

Spatial

Temporal