Lecture 22 - Genomic Imprinting and Dynamic Mutation'

Question 1

Epigenetic trait?

Answer 1

stable heritable phenotype resulting in chromosomal but not DNA changes

Question 2

Epigenetics examples?

Answer 2

DNA methylation, microRNAs, histone methylation and other modifications, RNA methylation

Question 3

DNA methylation?

Answer 3

at CpG region, causes transcription silencing, contributes to X chromosome inactivation

Question 4

Genomic imprinting?

Answer 4

restriction of expression to either mother or father allele, causes different expresion from genetically identical alleles

Question 5

Genomic Imprinting cause?

Answer 5

gamete-specific proteins binding imprinted genes during gametogenesis and embryogenesis

Question 6

Prader-Willi syndrome?

Answer 6

paternal allele of chrom15 deleted, maternal cannot take over due to silencing

Question 7

Angelman Syndrome?

Answer 7

maternal allele of chrom15 deleted, paternal cannot take over due to silencing

Question 8

Cancer and methylation?

Answer 8

Methylation of sequences coding for inhibitory factors deactivates them promoting tumour growth

Question 9

Dynamic Mutation?

Answer 9

Progressive expansion of repeated sequences e.g. huntingtons; symptoms of later generations occur earlier - anticipation

Question 10

Anticipation?

Answer 10

increasing disease severity or earliness of onset, most common in paternal inheritance (instability of CAG repeat in spermatogenesis)

Question 11

Molecular Genetic Testing for dynamic mutation?

Answer 11

Diagnostic, predictive, prenatal

Question 12

Genetic Counselling/Problems with asymptomatic at-risk patients?

Answer 12

testing lacks timely and severity specificity, pre-test interviews to assess motives, conselling regarding problems following diagnosis, implications for at-risk family, informed consent and confidentiality, long term follow up