Genetics Unit 19: Developmental Genetics

Front 1

3 stages of development

Back 1

1) preimpantation period - Ovulation and fertilization to end of second week
2) Embryonic period - 3rd to 8th week post conecption. Critical stage for development, where malformations may occur
3) Fetal period - 9th week till birth, fetus increases in size and organ system maturation

Front 2

What three genes show sequence homology with developmental regulatory genes in Drosophila?

Back 2

1) Hox genes
2) Pax genes
3) Genes that encode transcription factors containing zinc fingers

Front 3

4 steps in protein synth where regulation/modification of expression can occur.

Back 3

1) Regulation of which nuclear genes are converted to nuclear RNAs
2) RNA processing determines which RNAs will enter cytoplasm as mRNAs
3) Regulating which mRNAs are translated into proteins
4) Protein modification determines which proteins become functional, are internalized, or secreted.

Front 4

Consequence of PAX 1 Mutation

Back 4

Possible anomalies of intervertebral discs

Front 5

Consequence of PAX 2 Mutation

Back 5

Wilms tumor
Kidney anomalies
Retinal colobommas

Front 6

Consequence of PAX 3 Mutation

Back 6

Waardenburg syndrome

Front 7

Consequence of PAX 6 Mutation

Back 7

Aniridia (no iris)

Front 8

Waardenburg syndrome general features

Back 8

1) Autosomal dominant disorder
2) Cause of 2-3% of congenital deafness
3) Have a loss of function mutation in PAX 3

Front 9

Waardenburg syndrome type 1

Back 9

1) Sensorineural hearing loss
2) Pigment abnormalities - white forelock of hair, white eyelashes, irides of dif. colors, patches of hypopigmented skin.
3) Facial abnormalities - Lateral displacement of inner canthi of eyes (dystopia canthorum), broad nasal bridge
4) Neural tube defects

Front 10

Waardenburg syndrome type 3

Back 10

1) Hearing loss
2) pigment abnormality
3) facial abnormality
4) Limb defects

Front 11

Zinc finger genes

Back 11

Common in DNA binding proteins which bind promoters. Fingerlike projections form complex with zinc. Important in developmental regulation

Front 12

Greig Syndrome

Back 12

1) caused by mutation in multiple zinc finger genes on chromosome 7. DNA binding activity is lost (GLI3 mutation).
2) -Syndactyly
-polydactyly
-bifid thumb and big toe
-expanded cranial vault
-high forehead
-advanced bone age

Front 13

ZPA

Back 13

Cells in the posterior mesenchyme known as the zone of polarizing activity which determines the A-P axis of limb.

Front 14

Shh

Back 14

Sonic hedge hog gene. Is gene for ZPA signaling molecule. Can induce expression of Hox Genes.

Front 15

HoxD13 mutation

Back 15

1) Autosomal dominant
2) -syndactyly (webbing between 3rd and 4th finger)
-polydactyly of 4th finger
-polydactyly of 5th toe
-syndactyly of 4th and 5th toes
-aplasia/hypoplasia of middle phalagnes of toes

Front 16

Leri Weilly Syndrome (dishondrosteosis)

Back 16

Dominant form of mesomelic dwarfism. Heterozygote SHOX gene mutation. Coorelated with mutation in the SHOX gene on X chromosome (short stature homeobox containing gene). Causes:
-short stature
-madelung deformity of forearm

Front 17

Langer mesomelic dwarfism

Back 17

Homozygous mutation in DCS loccus of SHOX gene. More severe than DCS.

Front 18

Holoprosencephaly

Back 18

Causes by Shh disorder. Single incisor, single nostril, other bad stuff.

Front 19

Smith-Lemli-Opitz syndrome

Back 19

Caused by a metabolic cholesterol deficiency via lack of enzyme leading to malfunction of Shh which needs to be bound to cholesterol to be active.
Causes:-Bilateral or unilateral post axial polydactyly
-Excessive whorls on fingertips
-Y shaped cutaneous syndactyly of toes 2 and 3
-Host of other skeletal problems

Front 20

3 types of hedgehog genes

Back 20

1) Sonic - Important for midline patterning, limb developent, and CNS and skeleton development.
2) Desert - Genital development
3) Indian - Cartilage/bone mineralization

Front 21

Basal Cell Nevus syndrome (and gorlin syndrome)

Back 21

Caused by Patched 1 or 2 disorder causing smoothened disorder.
Causes: Wide, flat face, broad jaw which may contain cysts, pits in palm of hands, calcification in brain.

Front 22

Rubinstein-Taybi syndrome

Back 22

Caused by mutation in genes encoding for CREB binding protein. Causes: - beaked nose swith protruding columella
-broad radially deviated great toes and thumb

Front 23

Saethre-Chotzen syndrome

Back 23

Caused by a complete deletion in TWIST gene.
Causes premature suturing of skull and abnormal head.