Chapter 2: Non-Mendelian Genetics Flashcards
1
Q
trinucleotide repeats
A
- present throughout the genome, often necessary and functional
- usually stable through mitosis and meiosis
2
Q
Anticipation
- definition
- inheritance traits
- factors of anticipation
- how does severity increase
A
- increase in severity or or earlier onset of phenotype in successive generations
- progressive amplification of repeat number and can be seen in successive generations
- more repeats of trinucleotides may cause instability
- mostly seen through maternal anticipation
3
Q
Myotonic Dystrophy
- cause/symptom
- inheritance type
- spectrum of severity
A
- affects sustained skeletal and smooth muscle contractions (problems releasing),
- inherited through anticipation of trinucleotide repeats
- autosomal dominant inheritance pattern
- mild: mild myotonia
- classic: muscle weakness, myotonia, shortened life
- congenital: severe hypotonia, respiratory issue, early death
4
Q
Fragile X
- symptoms/causes
- inheritance pattern
- repeat expansion
- normal/intermediate/ premutation/full mutation number
- which region mutated and methylated
- anticipation?
- female severity
- premutation carriers
A
- X linked dominant
- long face, large ears, intellectual disability
- mutated gene located on X chromosome
- Fragile site (FMR1 region fully methylated; silenced)
- normal <45
- intermediate 45-54
- premutation: 55-200
- full mutation 200+
- CGG repeat expansion in FMR1 gene on X chromosome (anticipation)
- anticipation is not classic bc severity of intellectual disability does not increase with more repeats
- females with full mutation will have less severe conditions bc of lyonization
- premutation carriers have effects M: tremor and ataxia || F: early menopause
5
Q
mosaicism
- example of telling phenotype
A
presence of more than one cell line in an individual
- diff. skin pigmentation
6
Q
somatic mosaicism
- when mutation usually occurs
- severity factors
A
- mosaicism in body cells
- post-zygotic mutation
- severity depends on proportion of mutated cells in each tissue
7
Q
gonadal mosaicism
- where does mutation occur?
- example of gonadal mosaicism
- empiric recurrence risks
A
- mosaicism in gonads
- only in sperm/oocyte cells- individuals unaffected with condition
- mutation occurs in precursor egg or sperm cell
- achondroplasia: if unaffected father (no fam history) has kids that are both affected
- used to determine the risk that a disorder will recur
8
Q
Pallister-Killian syndrome
- phenotype
- which gene affected?
- non-mosaicism?
- mnemonic?
A
- hypopigmentation, extra nipples
- usually due to mosaicism
- non-mosiac is lethal
- mosaic tetrasomy 12p
- pigmented face, non-mosaic kills
9
Q
Genomic imprinting
- definition
- what results if this goes wrong
- how is it imprinted
A
- Specific M and F genes favored (genes expressed preferentially)
- different phenotypes may result (not great, refer to prader-willi and angelman syndromes)
- methylation
10
Q
UPD
- what it stands for
- definition
A
- Uniparental disomy
- 2 copies from M/F and none from the other
- not all results in phenotype (may play a role in unexplained pregnancy loss)
11
Q
Genomic imprinting malfunction mechanisms
- different ways genomic imprinting can screw up
A
- UPD
- Heterozygous deletion
- mutation in gene
12
Q
Heterozygous deletion
A
alleles differing by an insertion or deletion
13
Q
Russel Silver Syndrome
- cause/symptom
- mode of inheritance
- mnemonic
A
- growth disorder, small triangular face
- 10% maternal UPD chromosome 7
- ## UPD
14
Q
Triploidy
A
presence of 3 sets of chromosomes instead of 2
15
Q
Digynic triploidy
- definition
- phenotype
- mnemonic
A
- 2 sets of F chromosome + 1 set of M
- small fetus and small placenta
