Chapter 2: Non-Mendelian Genetics Flashcards Preview

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Flashcards in Chapter 2: Non-Mendelian Genetics Deck (20):
1

trinucleotide repeats

- present throughout the genome, often necessary and functional
- usually stable through mitosis and meiosis

2

Anticipation
- definition
- inheritance traits
- factors of anticipation
- how does severity increase

- 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

Myotonic Dystrophy
- cause/symptom
- inheritance type
- spectrum of severity

- 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

Fragile X
- symptoms/causes
- inheritance pattern
- repeat expansion
- normal/intermediate/ premutation/full mutation number
- which region mutated and methylated
- anticipation?
- female severity
- premutation carriers

- 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

mosaicism
- example of telling phenotype

presence of more than one cell line in an individual
- diff. skin pigmentation

6

somatic mosaicism
- when mutation usually occurs
- severity factors

- mosaicism in body cells
- post-zygotic mutation
- severity depends on proportion of mutated cells in each tissue

7

gonadal mosaicism
- where does mutation occur?
- example of gonadal mosaicism
- empiric recurrence risks

- 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

Pallister-Killian syndrome
- phenotype
- which gene affected?
- non-mosaicism?
- mnemonic?

- hypopigmentation, extra nipples
- usually due to mosaicism
- non-mosiac is lethal
- mosaic tetrasomy 12p
- pigmented face, non-mosaic kills

9

Genomic imprinting
- definition
- what results if this goes wrong
- how is it imprinted

- Specific M and F genes favored (genes expressed preferentially)
- different phenotypes may result (not great, refer to prader-willi and angelman syndromes)
- methylation

10

UPD
- what it stands for
- definition

- 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

Genomic imprinting malfunction mechanisms
- different ways genomic imprinting can screw up

- UPD
- Heterozygous deletion
- mutation in gene

12

Heterozygous deletion

alleles differing by an insertion or deletion

13

Russel Silver Syndrome
- cause/symptom
- mode of inheritance
- mnemonic

- growth disorder, small triangular face
- 10% maternal UPD chromosome 7
- UPD
-

14

Triploidy

presence of 3 sets of chromosomes instead of 2

15

Digynic triploidy
- definition
- phenotype
- mnemonic

- 2 sets of F chromosome + 1 set of M
- small fetus and small placenta

16

Diandric triploidy
- definition
- phenotype
- mnemonic

- 2 sets of M chromosome + 1 set of F
- huge placenta, normal-ish fetus

17

Cystic Fibrosis
- cause/symptoms
- mode of inheritance
- how can carrier mother give to child
- which gene mutated and why it causes phenotype

- thick mucus layer (respiratory problems
- autosomal recessive
- UPD (both X)
- CFTR gene regulates Cl ions

18

Prader - Willi
- definition
- symptom
- Mnemonic?

- specific deletion of male gene in parts of chromosome 15
- obesity (hyperphagia), intellectual disability
- no prader no father

19

Angelman
- definition
- symptom
- mnemonic?

- specific deletion of male gene in parts of chromosome 15
- severe intellectual disability, movement disorder
- prader-willi and angelman

20

Trinucleotide repeat disorders
- list all (3)
- bonus if you can list mode of inheritance, symptoms, cause

- Myotonic Dystrophy (CTG)
autosomal dominant muscle cant let go
- Huntington's (CAG)
mutation in FTT gene, huntington aggregate in cells (bypass transport system) Autosomal dominant
- Fragile X (CGG)
mutation in FMR1 gene on X chromosome (intellectual disability) X-linked dominant