W01_07 Non-classical genetic mechanisms Flashcards Preview

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Flashcards in W01_07 Non-classical genetic mechanisms Deck (14)
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1
Q

which nuclear base does methylation act on?

A

cytosine

2
Q

what happens to a gene that’s methylated?

A

it’s suppressed

3
Q

x-inactivation is from which mechanism?

A

methylation

4
Q

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

A

ok

5
Q

define imprinting

A

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

6
Q

define mosaicism

A

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

7
Q

neurofibromatosis is marked by which clinical symptoms?

A

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

8
Q

note: neurofibromatosis is a mosaic disorder

A

ok

9
Q

note: mitochondrial dna is maternally inherited

A

ok

10
Q

how many genes in the mitochondrial genome?

A

37;

16.5 kb circular chromosome

11
Q

note: mitochondrial heteroplasmy = mitochondrial mosaicism

A

ok

12
Q

what causes fragile x syndrome?

A

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

13
Q

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

A

premature ovarian failure, tremor-ataxia syndrome, neuropsychiatric diagnoses

14
Q

what’s anticipation?

A

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

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