Zaidi 1 Development 1

Question 1

Describe the development of multicellular organisms

Answer 1

1. organisms begin as a single cell
2. differentiate into different cell types
3. genomes are identical but the expression of the genes are different
4. gene expression controls development

Question 2

What are the 4 stages of the development of an embryo?

Answer 2

1. cell proliferation
2. cell specialization
3. cell interaction
4. cell movement

Question 3

True or false: homologous proteins are functional interchangeable

Answer 3

True

Question 4

Define blastula

Answer 4

a hollow filled ball of cells that forms shortly after the genome is activated following fertilization

• has a sheet of epithelial cells that faces the external medium which gives rise to the ectoderm

Question 5

Define gastrula

Answer 5

has 3 major layers; blastula undergoes massive rearrangements

Question 6

Describe the development of cells including the characteristics of multicellular organism development.

Answer 6

All begin as as single cell and will differentiate into different cell types.

Genome will have different gene expression

cells have memory and retain record of the signals and ancestors

basic machinery is the same for all organisms

Question 7

Describe what happens to the zygote after fertilization

Answer 7

1. zygote divides rapidly to form many small cells that get the nutrients from he egg itself
2. genome is inactive
3. genome is activated and cells divide to form a blastula
4. blastula undergoes massive rearrangements to form a gastrula

Question 8

define ectoderm

Answer 8

precursor of the nervous system and epidermis

Question 9

Define endoderm

Answer 9

precursor to the gut, lung, and liver

Question 10

Define mesoderm

Answer 10

precursor of muscles and connective tissue

Question 11

Describe the relationship between the ectoderm, endoderm, and the mesoderm

Answer 11

part of the epithelial sheet of the ectoderm tucks in and forms the endoderm. Cells move in-between those spaces and forms the mesoderm

Question 12

Define gastrulation

Answer 12

transformation of the blastula into a layered structure with a gut (has future mouth and future bootyhole)

Question 13

Describe the development program amongst organisms and what makes one different from the other?

Answer 13

The interaction manual is in the non-coding regulatory DNA associated with each gene.

the DNA has regulatory elements that allow the gene regulatory proteins to bind

The coding sequences are similar in DNA but its the NONcoding sequences that provide uniqueness

Question 14

Describe cell fate and the multiple fates that can occur

Answer 14

Cells will make decisions before showing signs of differentiation

determined cell fate- cells that will turn into specialized cells despite environment changes

completely undetermined- cells that can change rapidly due to alterations in env

committed- cells that have some attributes of a cell type but can change with the env

Question 15

What must occur before a cell acquires a fate?

Answer 15

It must express genes that are markers of their location or regionally determined

share positional value and retain memory of this

Question 16

Describe cellular differentiation

Answer 16

can happen bc of…

• asymmetric division
• molecules being distributed unequally
• changes in environment which are cued to the cell by signals from neighboring cells

Question 17

Define inductive signaling

Answer 17

induction of a different developmental program in select cells in a homogenous group leading to altered character

Question 18

What are the different types of inductive signals?

Answer 18

short range (cell to cell) and long range (substances that can diffuse through the extracellular medium)

Question 19

Define morphogen and describe how it works

Answer 19

a morphogen is a long range inductive signal that imposes a pattern on a field of cells

-forms gradients of different concentrations that can lead to different developmental pathways

Question 20

Describe how the morphogen forms its gradient and the characteristics of said gradient

Answer 20

• inducer diffuses away from its source and an inhibitor diffuses away from the source while blocking the action of a uniformly distributed inducer- basically provides balance
• has an on off signal using antagonists or extracellular inhibitors

Question 21

Describe delta notch signaling and how it relates to lateral inhibition

Answer 21

At first, all of the cells start off the same expressing both the Notch and the delta. Each cell however, wants to specialize and become the best of the best (mother cell), so it starts sending out inhibitory messages to the surrounding cells to try to get to them in a place where they are not able to have the delta and the notch factors. Eventually one of the cells wins the battle and is able to specialize into the cell that it wanted to become. But as the other cells are being beat out by the bully, they are not able to inhibit surrounding cells and become specialized themselves, leading to lateral inhibition. A lot like premed and medical school LOL

Question 22

Describe how there is diversity in patterns in the cell… (3 ways and describe them)

Answer 22

1. combinatorial control- the response of a cell to a given signal may differ based on the presence of other signals (combinations create variety) They cannot respond to everyone. Think of it like if you’re in a crowded room and there are a bunch of people talking at you, you are going to get a jumbled mix of conversation.
2. cell memory- effect of a given signal depends on previous experiences of the cell (alterations or whatever)
3. signal induction- different signals secreted in a spatial and temporal manner