Genetics

Question 1

Describe the 3 common forms of Mendelian inheritance [?]

Answer 1

• Autosomal dominant inheritance: one allele leads to expression of a given phenotype 50% chance of phenotype expression
• Autosomal recessive inheritance: allel does not lead to phenotype expression 25% of phenotype expression
• Sex-linked inheritance: phenotypic exprssion is determined by allel of sex chromosome Males: 50% chance / females: 50% chance

Question 2

Q: Describe 5 non-Mendelian inheritance patterns [?]

Answer 2

1- Mitochondrial inheritance – maternal mitochondria inherited from ovum
2- Dynamic mutation - trinucleotide repeats
3- Genetic imprinting – expression depends on parent of origin, 1 allele is silenced = imprinted
4- Mosaicism – presence of two or more populations of cells with different genotypes in one individual who has developed from a single fertilized egg
5- Uniparental disomy – offspring inherits both copies of a chromosome pair from a single parent

Question 3

Q: Briefly describe the plain radiographic views of the head [?]

Answer 3

• Lateral – View foreign bodies, sphenoid sinus, posterior frontal sinus wall
• Lateral oblique – View mandibular fractures
• Townes – Half-axial antero-posterior, 30 degrees down; AP; view skull, foramen magnum
• Caldwell – Occipitofrontal or posteroanterior; view frontal sinuses, NOE; PA 15-20 degrees
• Waters – Occipitomental, head tipped back; view maxillary sinuses; 45 degrees PA
• Submentovertex – Base projection; view zygomatic arches, posterior ethmoids, sphenoid