Molecular Genetics and Early Embryonic Development

Question 1

Paradigm of Development

Answer 1

• In every species and at every level of
organization, complex structures are made
by repeating a few basic themes with
variations.

Question 2

Stages of Embryonic Development (3)

Answer 2

differentiation
growth
patterning

Question 3

Differentiation:

Answer 3

cells begin to form specific

and specialized structures.

Question 4

Growth:

Answer 4

cell divisions that form more cells

with identical functions as the parental cell.

Question 5

Patterning:

Answer 5

cells produced by cleavage get
organized into layers and groups of cell
masses through what is known as
gastrulation.

Question 6

Patterning needs to occur in 3 dimensions (3)

Answer 6

– Anterior-Posterior (top-bottom)
– Dorsal-Ventral (left-right)
– Proximal-Distal (front-back)

Question 7

Malocclusion syndromes (3)

Answer 7

– Pierre-Robin
– Treacher Collins
– Marfan syndrome

Question 8

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Craniofacial malformations (4)

Answer 8

– Crouson
– Apert
– Pfeiffer
– Clefting syndromes (lip and palate)

Question 9

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• Bone Mass Traits (3)

Answer 9

– Sclerosteosis and van Buschem’s
– High Bone Mass and OPPG
– Paget’s Disease

Question 10

Tooth Development Disorders (2)

Answer 10

– Dentinogenesis Imperfecta

– Amelogenesis Imperfecta

Question 11

Craniofacial Anomalies Account for ~— of

All Congenital Defects

Answer 11

1/3

Question 12

Important Concepts of Embryonic

Development (4)

Answer 12

• Universal Mechanisms of Animal 
Development
• Proteins can be substituted across species
• Inductive signaling
• Regional Determination

Question 13

Multicellular animals are enriched in proteins mediating (2)

Answer 13

cell interactions and gene regulation

Question 14

Regulatory DNA defines the

Answer 14

development

program

Question 15

Asymmetric versus Symmetric Cell

Division

Answer 15

sister cells born different

sister cells become different as result of influences acting on them after their birth

Question 16

Inductive Signaling and Morphogens (2)

Answer 16

– Gradients reflective of a balance between
positive and inhibitory inductive signals
– Sequential Induction

Question 17

Inductive Signaling (4)

Answer 17

• Starting Point (cell or cell cluster)
• Cell – cell signaling
• Cell signaling cascades
• Acts over great distances

Question 18

Gastrulation

Answer 18

• Early developmental process in which the embryo (week 3
in humans) transforms from a single cell layer (blastula)
into the three primary germ layers

Question 19

Gastrulation
• Early developmental process in which the embryo (week 3
in humans) transforms from a single cell layer (blastula)
into the three primary germ layers:

Answer 19

– Ectoderm
– Endoderm
– Mesoderm

Question 20

Craniofacial Syndromes
• >--- distinct syndromes
• Significant cause of --- ---
• --% of all live births exhibit some form of 
minor or major abnormality

Answer 20

700
infant mortality
3

Question 21

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Craniofacial Development

Answer 21

• Neural tube development and closure
• Formation of ectoderm, somites, mesoderm and other cell masses
• Neural crest cell development, differentiation and migration
• Tissue-tissue interactions
• Tissue specific patterns of gene expression
• Reciprocal Induction
• Growth and mineralization of bones and teeth
• Neural development
• Muscle development

Question 22

Neural Crest Cells

Answer 22

• Embryonic cell population that is localized between the
developing neural tube and the epidermis. (there are also
adult neural crest cell like cells that have been identified in
many tissues)

Question 23

Some neural crest cell exhibit “stemness” in that they can

Answer 23

give rise to multiple differentiated cell types

Question 24

In the formation of the craniofacial structures (and many
other structures) the neural crest cells migrate through
restricted pathways to form the

Answer 24

developing structures.

Question 25

Cell migration is a tightly regulated processes and the
NCCs receive cues such as (2)
that restrict their movement and determine fate.

Answer 25

morphogens and growth factors

Question 26

Over — genes identified that have
mutations associated with tooth patterning,
morphogenesis defects and cell
differentiation defects

Answer 26

300

Question 27

As a collective group — genetic

diseases are the most common

Answer 27

craniofacial

Question 28

Ectodermal dysplasias (2)

Answer 28

– >100 different disorders
– Commonly involves one or more of teeth, nails, skin, sweat glands
and/or hair

Question 29

Tooth Agenesis
– Hypodontia:
– Oligodontia:
– Anodontia:

Answer 29

missing only a few teeth
missing more than 6 teeth, excluding third molars
absence of teeth

Question 30

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Genetic Diseases of the Dentition (5)

Answer 30

Ectodermal dysplasias
Tooth Agenesis
Supernumerary Teeth
Cleft Lip/Palate (OMIM lists 565 entries)
Skeletal Diseases and the Dentition

Question 31

Microdontia:

Answer 31

one or more teeth appear smaller

Question 32

Macrodontia:

Answer 32

one or more teeth grow faster and

exceed average size

Question 33

The prevalence of genetics diseases
involving the — skeleton present a
high likelihood that as a dentist you will
encounter one these challenging cases in
your practice. Especially, if you practice in
an academic setting, the chances are high
that you may consult on the treatment and
management of these cases.

Answer 33

craniofacial