Developmental Biology

Question 1

Embryogenesis

Answer 1

process that makes a single-celled zygote into a multicellular embryo

Question 2

What happens after fertilization?

Answer 2

cleavage

Question 3

cleavage

Answer 3

rapid cell division without any growth between division events

Question 4

Blastula

Answer 4

when cleavage is complete, the embryo consists of a mass of blastomere cells with an inner cavity known as the blastocoel

Question 5

Potency of blastomere cells

Answer 5

multipotent

can develop into more than one cell type

Question 6

Monozygotic twins

Answer 6

come from the same zygote, but their blastomeres are separated in an early stage

fertilized by the same sperm

Question 7

Dizygotic twins

Answer 7

occur from two independent fertilization events

fertliized by two different sperms

Question 8

Gastrulation

Answer 8

extensive and highly organized movements that radically rearrange the embryonic cells into a structure called gastrula

Question 9

When does gastrulation begin?

Answer 9

with the formation of an opening called a blastopore

cells move towards the blastopore to form a tube-like structure (the gut)

Question 10

Germ layers

Answer 10

created during gastrulation

known as ectoderm, mesoderm, and endoderm

Question 11

Ectoderm

Answer 11

ectoderm cells on the surface of the gastrula will give rise to the entire nervous system

Question 12

How do cells know how to specialize?

Answer 12

through communication

Question 13

stem cells

Answer 13

able to self renew (copy themselves) or differentiate

totipotent

Question 14

potency

Answer 14

developmental potential (ability to become other cell types)

Question 15

totipotent

Answer 15

can give rise to all lineages (including placenta)

Question 16

pluripotent

Answer 16

can give rise to all cell types of the body

Question 17

multipotent

Answer 17

can develop into more than one cell type

Question 18

unipotent

Answer 18

can only produce one type of cell

Question 19

Morphogens

Answer 19

mRNA molecules that help establish the basic anterior/posterior coordinates

pattern formation molecules that are present in a concentration gradient

Question 20

Bicoid

Answer 20

a type of morphogen that develops anterior structures

Question 21

Maternal effect genes

Answer 21

genes transcribed in the ovarian (“nurse”) cells that surround the developing egg

morphogens are an example

Question 22

How does Bicoid work?

Answer 22

it is a regulatory transcription factor that activates many genes when turned on

Question 23

nanos

Answer 23

an RNA binding protein that helps to develop the posterior coordinate

affects translation, whereas Bicoid affects transcription

Question 24

Bicoid and nanos

Answer 24

are present in opposing concentration gradients

this allows one end to develop anterior structures and the oppossing end to develop posterior structure

Question 25

Stages of development/genes

Answer 25

early in development gap genes define general position of head, thorax, and abodominal region

later, pair-rule genes define the edges of individual segments

finally, homeotic genes are expressed along the length of the body and tell the segments what to become

Question 26

Homeotic/hox genes

Answer 26

determine that one part of an animal will be morphologically distinct from another

Hox genes code for transcription factors

Question 27

Homeobox

Answer 27

a DNA sequence that is required for the expression of hox genes

encodes for the homeodomain, which binds consensus DNA sequences in the promoters of many downstream, target genes

homeobox sets into motion a series of events

Question 28

Homeotic transformation

Answer 28

the development of a dramatic mutation in invertebrates where a structure is located in the wrong place

Question 29

Why do we not see homeosis in vertebrates?

Answer 29

we have 4 families of Hox genes, while invertebrates only have 2, so it makes it harder to mutate

Question 30

What are the four families of Hox genes considered?

Answer 30

paralogus

have a similar DNA sequence and A/P position

Question 31

What happens if there are no Hox genes?

Answer 31

there is no variation in morphology

Question 32

What is something that vertebrates have that invertebrates do not have when it comes to Hox genes?

Answer 32

Retinoic acid

Communicates what Hox genes are going to be expressed where

Exists in a concentration gradient

Lack of retinoic acid can lead to extreme birth defects