Genetic Diseases in Craniofacial Morphology and Dysmorphology Flashcards

1
Q

What are the outcomes of the Human Genome Project (HGP)?

A
  • Identified all the approximately 20,000-25,000 genes in human DNA and the sequences of the 3 billion chemical base pairs that make up human DNA
  • Stored this info in databases, making it available for data analysis
  • Has begun to address the ethical, legal and social issues that arise from the project
  • Has catalyzed the multibillion-dollar U.S. biotechnology industry and analyses of the data will continue for many years.
  • Potential medical benefits through gene testing, gene therapy and pharmacogenomics.
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2
Q

What is Homeobox genes?

A
  • Homeotic “master” genes
  • encoding for transcription factors
  • involved in patterning, induction, apoptosis
  • Control of epithelial/mesenchymal interaction
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3
Q

How does Homeobox genes work?

A
  • Through the neural crest cells (NCC)
  • Ectomesenchyme of first branchial arch derived from NCC
  • Migration directed by homeobox genes
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4
Q

What is the origin of facial mesenchyme?

A

Neural crest

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5
Q

What is the Morphogenetic Cascade?

A

The basic morphogenetic processes of initiation, segmentation, patterning, migration and differentiation are mediated via a series of extracellular signalling milecules in a cascade of cellular events

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6
Q

What is the homeobox genes and tooth development?

A

MSX1 and MSX2 in the initiation developmental position (patterning) and morphodifferentiation of tooth buds

Info expressed thorugh mesenchymal growth factors (FGF, EGF, TGFs and BMPs)

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7
Q

What does one gene, many genes and one gene affecting different charaters mean?

A

One gene = one protein

Many genes = one character

One gene affecting different charaters mean = Pleiotropy

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8
Q

What does Penetrance and Expressitivity mean?

A

Penetrance: probability that presence of disease genotype will cause disease

Expressitivity: Variation in the severity of expression of a particular gene

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9
Q

What is X-linked inheritance recessive?

A
  • more common
  • only males affected - females are carriers
  • affected males may not survive or lack reproductive fitness
  • female carrier transmits allele to half her sons and half daughters will be carriers
  • male can transmit to daughters but not to sons
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10
Q

What happens in X-linked inheritance?

A
  • Heterozygous female may show features of the condition
  • due to non-random X-inactivation
  • if X-chromosome with mutant allele remains active in some cells (disease)
  • In those with normal allele - no disease manifestation
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11
Q

What is X-linked inheritance dominant?

A
  • Acts like AD in that 50% males and 50% females will be affected
  • more likely to be lethal in hemizygous males
  • Females also affected (not just carriers)
  • Rare - one craniofacial example being OFD syndrome
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