1-31 Epigenetics, Imprinting, Uniparental Disomy

Question 1

methylation (genome inprinting)

Answer 1

methylation of Cpg-rich regions in gene promoters cuases repression of gene transcirption into mRNA (and reduced production of the gene product)

methylation patterns are converved during cell division

methylation patterns may be inherited and/or affected by environement conditions

Question 2

Epigenetics

Answer 2

study of heritable changes in gene expression or cell phenotype caused by mech other than changes in the underlying DNA sequences

Question 3

pronuclear transplantation

Answer 3

proof of idea that you need gene set from a female and a male

if you pull out female genome of an egg and add in another male you make a

androgenetic ovum: good membrane/placenta formation poor embryo developmen (forms a hydatidiform mole)

gynogenetic: good embryo, poor membranes/placenta (teratoma)

Question 4

Prader-willi syndrome

Answer 4

baby: hypotonia, failture to thrive
child: obesity, hyperphagia
characteristic facies
small hands/feet
hypogonadism
deletion of 15q in 70% of cases ALWAYS the paternal chromosome

Question 5

uniparental disomy

heterodisomy
isodisomy

Answer 5

both copies of a chromosome from 1 parent

if imprinted genes on that chromosome, there may be a phenotype because of lack of expression of genes from other parent chrom

heterodisomy: receive both chrom copies from 1 parent but receive their maternal and paternal chroms
isodisomy: duplication of same chromosome from 1 parent (identical)

Question 6

Number of human genes

Answer 6

20,000

Question 7

Beckwith-Wiedemann syndrome

Answer 7

big tongue, big liver, omphalocele, renal problems, ear creases, tumors

caused: loss of methylation of imprinting center on maternal chrom 50%, paternal uniparental disomy 20%, others…

Question 8

Hereditary glomus tumors

Answer 8

skipped generations but dominant (?)

expression of tumor occurs when nuclear autosomal gene is inherited from the FATHER

shows that this gene is different on the maternal vs paternal chromosome

Question 9

Angelman syndrome

Answer 9

baby: growth deficiency
severe intellectual disability, inapprorpirate laughter, ataxia, sizures

deletion of arm in 70% of cases ALWAYS the maternal chromosome

point mutaitons in UBE3A in 10% of cases

imprinting center on chromosome 15 that acts different on maternal vs paternal chrom- silences different genes per inherited chrom

Question 10

Epigenetic reprogramming of primordial germ cells

Answer 10

primary oocyce has imprint from a womens parental chromosomes–>gametogenesis makes a haploid egg cell–>De-methylation of the inherited imprint –> remethylation to give it the maternal imprint so that fetus inherits the maternal print