SMB Conditions & Diseases

Question 1

Ameila

Answer 1

complete absence of limbs due to errors in induction, pattern formation

Question 2

Meromeila

Answer 2

partial absence of limbs due to errors in induction, pattern formation

Question 3

Syndactyly

Answer 3

abnormal fusion of digits which can occur in hands and/or feet. They may be fused via skin only or the bones may be fused as well. Due to errors in patterning/programmed cell death

Question 4

Polydactyly

Answer 4

too many digits [hands/feet]; results from an abnormal expansion/division of the apical ectoderm ridge [AER]

Question 5

Crainosynostosis

Answer 5

premature ossification of the sutures in the brain. This prevents normal skill and brain growth and it can cause the skull to twist and deform

Question 6

Hemivertebra

Answer 6

incorrect fusion of one half of vertebra: only one side is formed correctly; one of the most common causes of scoliosis; affects 1:2000 patients [probably more]; you can also get complete fusion of two vertebrae [effectively lose a vertebra due to errors in this process]

Question 7

Achondroplasia

Answer 7

premature/abnormal ossification of chondrocytes results in defective bone growth [particularly affects long bones; most often due to mutation in fibroblast growth factor receptor 3 [FGFR-3]; affects 1:5-10K live births; most mutations are sporadic

Question 8

spondylocostal dystosis

Answer 8

mutation in Notch signaling which results in segmentation defects; this specific disorder leads to a malformation of the vertebral column, ribs, and a shortened thorax