Devel II

Question 0

General mode of action of GF - signalling cell secretes GF –> GF diffuses to nearby cells –> binds to receptor –> changes intracellular & transcription properties of cell –> protein expression…final effect is change in protein synthesis

Answer 0

j

Question 1

Cells release small diffusible proteins = ___ into extracellular environment. When these factors are receive by __ on another cell, they can bring about number of change to cell’s behavior including ___ (4). Obviously all of these responses are potentially important for regulating embryonic development.

Answer 1

growth factors - secreted proteins that certain level of diffusion…fill in; specific receptors

stimulation/inhibition of cell proliferation, differentiation, cell shape change & stimulation/inhibition of cell migration

Question 2

TGF-beta1-3. Bone morephogenetic proteins (BMPs). Receptors are ___ kinases - they modify intracellular proteins by adding phosphage to ___/___

Answer 2

Overall, there are about 30 family members in humans.

Threonine/series kinase; Serine or threonine

Question 3

The __ growth factor family - they’re are about 20 different __ proteins in mammals. All are expressed in the embryo

Answer 3

Wnt - wingless & human oncogene called int

Wnt

Question 4

The __ GF - there are 3 of them. There are called sonic hedgehod, indian hedgehog & desert hedgehog

Answer 4

hedgehog - absolutely essential gene

Question 5

There are other GF including

Answer 5

FGFs, PDGFs, EGFs, VEGFs…

All of these proteins bind to specific receptors

Question 6

Even with this large # of GF, exactly same proteins are used for regulation of numerous different developmental events - For example, ___ is active during blood formation, neural development, lung development & growth

Answer 6

BMP4

Question 7

Given potency of GF, their expression is very closely regulated. Regulation occurs at level of ___(4)

Answer 7

transcription, mRNA processing & stability, translation & post-translational activity

Question 8

What are examples of post-translational regulation? BMP family proteins are bound by inhibitors = __ & ___. Wnt family proteins are bound by inhibitors called __ & ___. Hedgehob is bound by an inhibitor called ___. All of these inhibitors prevent GF from binding to their receptors, thus blocking signaling

Answer 8

inhibitors of GF activity;

noggin & chordin

dickkoph & crescent

Hedgehog interacting protein (hip)

Question 9

GF signaling is so fundamental to embryonic development that it’s very rare for embryos with GF defects to survive until birth. Approximately __ of all pregnancies fail to reach term. It’s probably that defects in GF signaling account for many of these spontaneous __.

Answer 9

50%; ?

Question 10

One relatively common example of birth …..

Answer 10

holoprosencephaly

Question 11

The brain may fail to form 2 lobes. At its most extreme, holoprosencephaly may present as cyclopia - telltale sign f loss of ___ signaling

Answer 11

Hedgehog

Question 12

At the large scale level, induction can be interpreted as 1 tissue (or region of embryo) instructing another region. Examples include ___

Answer 12

notochord inducing epidermis to form neural tissue
notochord inducing scleretome to form somites
endoderm induction of heart tissue
heart induction of liver tissue

Question 13

In fact, induction is the result of action by signaling proteins (GF/inhibitors). Ex - pattterning of somites

Answer 13

.

Question 14

Sonic hedgehog

Answer 14

fill in

Question 15

The heart forms mesoderm where Wnt signaling is blocked. This is achieved by Wnt inhibitors called ___. ___ is expressed in the ___

Answer 15

crescent; crescent; endoderm

Question 16

Notochord secretes ___ to inhibit BMP-4. Neural tissue forms where BMP-4 signaling is ___

Answer 16

noggin; absent

Question 17

What are homeobox genes? The homeobox encodes a DNA binding protein domain = ____

Answer 17

These are important for many aspects of embryonic development. All of these genes contain conserved DNA sequences called the homeobox.

homeodomain. All homeodomain proteins are transcriptional regulators - either positive or negative

Question 18

There are about __ homeobox genes in the human genome

Answer 18

150

Question 19

What are Hox genes? Mammals have __ Hox clusters.

Answer 19

subset of homeobox genes that provide positional informtion in the embryo. The Hox genes are arranged in cluster with up to 9 genes in a row on the chromosome.
4

Question 20

T/F The order of the genes is the same in human & fly

Answer 20

True! These genes must therefore have arisen in evolutionary ancestor of both mammals & insects

Fly has only 1 cluster; humans have 4 (was amplified)

Question 21

The higher the number of the gene, the more ___ (cranial/caudal) is the expression

Answer 21

caudal

Question 22

The expression of Hox genes marks a particular cranio-caudal address along body axis.

Answer 22

k

Question 23

If you have a lot of genes expressed, you are more ____(cranial/caudal)?

Answer 23

caudal

Question 24

More genes does not mean more complicated structure

Answer 24

.

Question 25

If Hoxc-8 is mutated, the first lumbar vertebra becomes rib-bearing. It has been transformed into more cranial structure

Answer 25

It is one notch more cranial

Question 26

Similarly if Hoxb-4 is mutated, cervical veretebra C2 takes on structural features like ___

Answer 26

C1. - more cranial

Question 27

What is a common defect of Hox mutations?

Answer 27

cervical ribs - 1% of population

Question 28

What are differentiation/determination genes?

Answer 28

These are genes that are responsiblie for directing differentiation of a specific cell/tissue type. They are sometimes called ____ becasue they ___ of many subordinate gees. FILLL INNN

Question 29

ModD is an example of ___ - name derived from ___

Answer 29

determination gene; myocyte determination

Question 30

What is myoD

Answer 30

small family of related muscle determination genes have been identified including myogenin, myf-5 & MRF-4.

MyoD can convert most cells into muscle cells - it can initiate entire muscle development program

Question 31

What is Pax6?

Answer 31

determination gene

This is a Homeodomain protein (NOT Hox protein). Remember that the Hox gene **

Question 32

If you express a Pax6 gene in the wrong location, what would happen?

Answer 32

you would grow an eye there!

Question 33

In the total absence of Pax6 function, they eye fails to form completely & there are neural defect that result in embryonic lethality. Absence of 1 pax6 gene (heterozygosit) ___

Answer 33

fill in