Genetics

Question 1

Dwarfism is caused by defect on which gene, on which chromosome? What is the inheritance pattern and what is the genotype of those affected?

Answer 1

Achondroplasia - FGF3 defect on Chromosome 4

–FGF is produced at apical ectodermal ridge - stimulates mitosis of underlying mesoderm - lengthening of limbs

Autosomal Dominant - Pts affected by dwarfism are HETEROZYGOUS (homozygous is not compatible with life)

Question 2

What is the Disease: Bilateral acoustic neuromas?

what chromosome is defective?

Answer 2

Neurofibromatosis type 2

Chromosome 22

Question 3

what is the inheritance pattern of Fanconi Anemia?

Answer 3

Autosomal Recessive - gene defect in proteins responsible for DNA repair

Question 4

What is the inheritance pattern of Fragile X syndrome?

Answer 4

X-linked dominant - expansion of CGG trinucleotide on the FMR1 gene (needed for normal neuro development)

Question 5

What is the inheritance pattern of Huntingtons?

Answer 5

autosomal dominant

Question 6

What is the inheritance pattern of Sickle Cells disease?

Answer 6

Autosomal recessive - inheritance of hemoglobin S

Question 7

What is an essential amino acid in patients with Phenylketouria?

Answer 7

Tyrosine

Question 8

What is the inheritance pattern of Polycystic Kidney disease?

Answer 8

Autosomal dominant

Question 9

What is the function of the Homeobox (Hox) gene? What happens when there is a mutation??

Answer 9

Cranio-caudal segmental organization

–mutation = appendages in wrong locations

Question 10

The genetic defect for Marfan’s syndrome is on what chromosome?

Answer 10

15

Question 11

Identify dz and mechanism of inheritance

78 yr old pt with very firm grip. Pt daughter and granddaughter rapidly clenching and unclenching before shaking hands

Answer 11

Myotonic dystrophy

• AUTOSOMAL DOMINANT
• CTG trinucleotide repeat expansion = Anticipation

-linked to instability during MATERNAL MEIOSIS