Molecular Genetics of Pattern Formation II

Question 1

Fruit fly as experimental system

Answer 1

Short gen time, low cost, genetic screen, conserved pathways

Question 2

House mouse as experimental sysetm

Answer 2

complex-more similar to humans

manipulable genetically

short generation time

Question 3

kocnouts

Answer 3

delete any gene via embryonic stem cells

Question 4

knckins

Answer 4

replace one version of gene with another by ES cells

Question 5

transgeneics

Answer 5

add extra copies of any gene (no removing DNA)

Question 6

ICM cells

Answer 6

Totipotent-retain totipotency in vitro-called ES cells

Question 7

How to make knockout/knock in?

Answer 7

Homologous recomb

grw ES cells in vitro, gernate DNA construct with DNA change in lab, introduce construct to ES cells, select cells that underwent homo recombination

Question 8

How to do transgeneics

Answer 8

get fert eggs from fallopian tubes

DNA injected into princely

DNA integrates randomly and then transmitted to offspring

Question 9

Homeotic mutations tell us

Answer 9

that there are genes in genome that control patterning or germination of structures

Question 10

Homeobox proteins facts

Answer 10

sequence of genes that are responsible for homeotic mutations

TFs form protein complexes in vivo to determine specificity

encodes protein domain called homeodomain
-recognize TAAT rich binding site in many promoters/enhacers

Homeobox genes encode Tf’s that result in cascade expression necessary for development of body structure

bind in sequence specific manner

Question 11

How many protein domain in homeobox tfs

Answer 11

homeodomain is only one protein domain in homeobox tf

• -other proteins interact with nonhomeodomain region of TF to form protein complex that then regulate DNA binding sepcificty/trx specificty
• other proteins influence DNA binding specificity by protein protein interaction in vivo and trx activity of homeobox domain

Question 12

2 classes of homeobox tfs

Answer 12

hoxgenes-mutation results in homeotic transformations

homeobox tf-play role in dev of structures and particular cell types

Question 13

consistent expansion in number of homeobox gnes

Answer 13

true in evolution from fly to mouse/human

Question 14

Hox genes

Answer 14

pattern body axis

expressed in specific embryonic domains and function in generation of that particular

positioned along chromosome in same order in which they are expressed along anterior-posterior axis in developing fly

conserved

Question 15

hox clusters

Answer 15

4 present in mouse/human

conservation and expansion in number-evolution

Question 16

orthologs vs paralogs

Answer 16

homologous gene between species

homologous gene within speices

Question 17

P-A axis is along what DNA directionality

Answer 17

5’ to 3’…?

Question 18

sclerotome

myotome

dermatome

Answer 18

skelton

skeletal muscles

dermis

Question 19

Spatial colinearly

Answer 19

genes furter 3’ have more anterior expression boundaries

Question 20

temperotal colinearilty

Answer 20

3; hx genes are expressed earlier in development than 5’ gene

Question 21

Hox code

Answer 21

different groups of cells express distinct patters of ox genes-depending on thier position along the anterior-posterior axis

Question 22

knockouts of hox genes

Answer 22

anterior transpformations

-single mutants aren’t as bad as double

Question 23

gain of function hox mutations

Answer 23

lead to posterior transformations

-too many posterior hox genes expressed in anterior

Question 24

transcriptional mech regulating hox

Answer 24

all ox coexpressed along same set of cells along A-P axis

• each HOX gene sits in specific gap
• if misexpresseed in another gap-it would make its gene there

Question 25

Formation of head

Answer 25

controlled by homeobox tf OTD
-otd expressed in anterior blastocyst-region of embryo that will give rise to anterior brain structures

in mouse/human otx1/2

Question 26

null otd, otx1-/-, otx2-/-

Answer 26

otd-/-=no anterior brain region develop

otx1-brain structures smaller

otx2-early CNS not formed

not having 1 is better than not having 2

sufficient and ncessary for brain creation
-on top of transitional cascade

Question 27

Ectopic expression

Answer 27

misimpression of old or txx in non neural tissues will generate neural structures

Question 28

how redudant is otx1 and otd?

Answer 28

functiaally equiblivalent-resuce otx-/- genotype

-otd can regulate same set of downstream genes as otx

Question 29

how are motor neurons genreated

Answer 29

cascade of homeobox tfs

• allow us to garnet motor neurons in culture-rescue some disease phenotypes
• these motor neurons are created by neuronal stem cells that a rea create though cascade of homeobox tfs

Question 30

what is tf code for embryonic stem cells

Answer 30

oct, sox, nanog-covnert other cells to iPS cells

Question 31

synpolydactily and hox genes

Answer 31

hox genes are important in patterning of limb

• mutation in hoxd13=limb patterning malformations
• missense mutations affected 3d configuration of ox gene