Biochem 85

Question 1

Define Uniparental Disomy

Answer 1

Offspring receive 2 copies of a chromosome from one parents and 0 from the other.

Question 2

Define Heterodisomy

Answer 2

Heterozygous - indicates a meiosis I error.

Question 3

Define Isodisomy

Answer 3

Homozygous - indicates a meiosis II error or postzygotic chromosomal duplication of one of a pair of chromosomes, and loss of the other of the original pair

Question 4

Define imprinting

Answer 4

At a particular locus, only one gene is active (other is methylated)

Deletion of the active gene -> disease

Question 5

Prader Willi and Angelman syndromes are due to mutation or deletions on which chromosome?

Answer 5

Chromosome 15

• can also occur due to uniparental disomy

Question 6

Prader-Willi Syndrome

Answer 6

Maternal imprinting

Question 7

Angelman Syndrome

Answer 7

Paternal imprinting

Question 8

Explain maternal imprinting in Prader-Willi

Answer 8

gene from mom is normally silent and Paternal gene is deleted/mutated

Question 9

Explain paternal imprinting in Angelman syndrome

Answer 9

gene from dad is normally silent and maternal gene is mutated/deleted

Question 10

What is the presentation of Prader-Willi?

Answer 10

Hyperphagia
Obesity
Intellectual disability
Hypogonadism
Hypotonia

Question 11

What is the presentation of Angelman?

Answer 11

“Happy Puppet”
seizures
ataxia
severe intellectual disability