Genomic Imprinting

Question 1

Biallelic Expression

Answer 1

Copies from each parent function equally in child

Question 2

Changes from infancy to childhood in Prader-Willi Syndrome

Answer 2

Infancy: hypotonia and feeding difficulties; Childhood: uncontrolled appetite and obesity

Question 3

Symptoms of Angelman Syndrome

Answer 3

Spasticity, seizures, seve MR, growth retardation

Question 4

PW and Angelman deletion is often on…

Answer 4

del(15)(q11q13)

Question 5

Epigenetic DNA modifications that influence gene expression are _____ but ______

Answer 5

heritable, reversible

Question 6

Type of epigenetic mechanism in which parent-of-origin effects are transmitted through gametes

Answer 6

imprinting

Question 7

Type of epigenetic mechanism that is heritable from cell to cell but not between generations

Answer 7

X inactivation

Question 8

Dynamic epigenetic mechanism

Answer 8

DNA methylation

Question 9

Maternal or paternal copy expressed? IGF2

Answer 9

paternal

Question 10

Maternal or paternal copy expressed? KVLQT

Answer 10

maternal (but expression is biallelic in the heart)

Question 11

Usually, imprinting is (on/off)

Answer 11

Off

Question 12

Maternal or paternal copy expressed? SNRPN

Answer 12

Paternal

Question 13

Maternal or paternal copy expressed in the brain? UBE3A

Answer 13

Maternal (but biallelic everywhere else)

Question 14

Imprinting control region; sets the imprint for multiple genes during gametogenesis

Answer 14

Bipartite ICR

Question 15

Why are maternal and paternal imprinting different?

Answer 15

One portion of ICR may be more active in males during gametogenesis, while one more active in females

Question 16

3 Steps in the Imprinting Cycle

Answer 16

1) Imprinting “switched” during gametogenesis (to the correct gender-specific methylations)
2) Pattern maintained during development and in the somatic tissues
3) In the gametes, imprinting is wiped clean then re-imprinted (in a way that reflects the parent’s gender) to pass onto the next generation

Question 17

How does parent-of-origin effect play a role in disease?

Answer 17

When there is only one allele that is typically active, disease occurs if that allele is disabled

Question 18

What disease results from a paternal deletion: del(15)(q11q13)?

Answer 18

PWS

Question 19

What disease results from a maternal deletion: del(15)(q11q13)?

Answer 19

AS

Question 20

What is the result of an unequal crossover between low copy repeats?

Answer 20

microdeletions

Question 21

How do hotspots relate to PWS?

Answer 21

The genes responsible for PWS (if deleted/disabled) are contained within regions where unequal crossover + microdeletions are frequent

Question 22

Causes of PWS (3):

Answer 22

Paternal deletion; maternal uniparental disomy (with no paternal copies); mutation in imprinting center

Question 23

Gene involved in PWS:

Answer 23

SNRPN

Question 24

Gene involved in AS:

Answer 24

UBE3A

Question 25

Causes of AS (4):

Answer 25

Maternal deletion; paternal uniparental disomy (no maternal); Mutation in imprinting center; UBE3A mutation

Question 26

Uniparental Disomy

Answer 26

Individual inherits both chromosomes of one homologous pair from a single parent (and none from the other parent)

Question 27

Cause of uniparental disomy:

Answer 27

2 separate nondisjunction events in gametogenesis/embryogenesis of individual

Trisomy rescue

Question 28

Trisomy Rescue

Answer 28

Trisomy cause by maternal meiotic nondisjunction is “fixed” by chromosome LOSS through mitotic nondisjunction

Question 29

Why does trisomy rescue occur?

Answer 29

There is a selective advantage