W01_07 Non-classical genetic mechanisms

Question 1

which nuclear base does methylation act on?

Answer 1

cytosine

Question 2

what happens to a gene that’s methylated?

Answer 2

it’s suppressed

Question 3

x-inactivation is from which mechanism?

Answer 3

methylation

Question 4

note: the quintuplets were 2/5 colourblind because of x-inactivation

Answer 4

ok

Question 5

define imprinting

Answer 5

the silencing of one set of alleles so that only the maternal or paternal allele is expressed;
note this is reset in the primordial germ cells

Question 6

define mosaicism

Answer 6

the presence of two cell lines in an individual, differing in genotype or karyotype, derived from a single zygote

Question 7

neurofibromatosis is marked by which clinical symptoms?

Answer 7

cafe-au-lait spots,
neurofibromas,
iris lisch nodules,
plexiform neurofibromas, blahblah

Question 8

note: neurofibromatosis is a mosaic disorder

Answer 8

ok

Question 9

note: mitochondrial dna is maternally inherited

Answer 9

ok

Question 10

how many genes in the mitochondrial genome?

Answer 10

37;

16.5 kb circular chromosome

Question 11

note: mitochondrial heteroplasmy = mitochondrial mosaicism

Answer 11

ok

Question 12

what causes fragile x syndrome?

Answer 12

triplet repeat expansion disorder.
there are a few CGG repeats in the FMR1 gene. if there are >200 of these repeats, then it leads to fragile x syndrome.
55-200 repeats = premutation

Question 13

what are clinical manifestations of premutation form of fragile x syndrome?

Answer 13

premature ovarian failure, tremor-ataxia syndrome, neuropsychiatric diagnoses

Question 14

what’s anticipation?

Answer 14

progressively earlier onset and/or increased severity in successive generations of a family, as they get more and more triplet repeats