Genes for embryogenesis; early fetal dev; errors in organ morphogen

Question 1

role in sonic hedgehog gene for embryogenesis

Answer 1

produced at base of limbs in zone of polarizing activity

Question 2

gene involved in patterning along anterior-posterior axis

Answer 2

sonic hedgehog gene

Question 3

mutation in sonic hedgehog gene causes what?

Answer 3

holoprosencephaly

Question 4

gene in CNS development

Answer 4

sonic hedgehog gene

Question 5

Where is Wnt-7 gene produced?

Answer 5

apical ectodermal ridge => thickened ectoderm at distal end of each developing limb

Question 6

What gene is necessary for proper organization of dorsal ventral axis?

Answer 6

Wnt-7 gene

Question 7

Where is FGF gene produced?

Answer 7

produced at apical ectodermal ridge

Question 8

What is the action of FGF gene?

Answer 8

stimulates mitosis of underlying mesoderm => providing for lengthening of limbs

Question 9

Role of Hox (homeobox) gene

Answer 9

involved in segmental organization of embryo in a craniocaudal direction

Question 10

Hox mutation causes what?

Answer 10

appendages in wrong locations

Question 11

day 0 in fetal development

Answer 11

fertilization by sperm forming zygote => initiating embryogenesis

Question 12

within week 1 in fetal development

Answer 12

hCG secretion begins after implantation of blastocyst

Question 13

within week 2 in fetal development

Answer 13

bilaminar disc (epiblast, hypoblast);
2 weeks => 2 layers

Question 14

within week 3 in fetal development

Answer 14

trilaminar disc => 3 weeks => 3 layers;
gastrulation;
primitive streak, notochord, mesoderm and its organization and neural plate begin to form

Question 15

weeks 3-8 in fetal development (embryonic period)

Answer 15

neural tube formed by neuroectoderm and closes by week 4;
organogenesis;
EXTREMELY SUSCEPTIBLE TO TERATOGENS

Question 16

week 4 in fetal development

Answer 16

heart begins to beat;
upper and lower limb buds begin to form;
4 weeks => 4 limbs

Question 17

week 8 (start of fetal period)

Answer 17

fetal movement;

fetus looks like a baby

Question 18

week 10 in fetal development

Answer 18

genitalia have male/female characteristics

Question 19

define gastrulation

Answer 19

forms trilaminar embryonic disc;

establish ectoderm, mesoderm and endoderm germ layers

Question 20

When does gastrulation start?

Answer 20

w/ epiblast invaginating to form the primitive streak

Question 21

define agenesis

Answer 21

absent organ due to absent primordial tissue

Question 22

define aplasia

Answer 22

absent organ despite present primordial tissue

Question 23

define deformation

Answer 23

extrinsic disruption;

occurs after embryonic period

Question 24

define hypoplasia

Answer 24

incomplete organ development;

primordial tissue present

Question 25

define malformation

Answer 25

intrinsic disruption;

occurs during embryonic period (wks 3-8)