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Flashcards in Patterns Of Inheritance Deck (9)
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List the patterns of Mendelian inheritance

Autosomal dominant
Autosomal recessive
X linked dominant
X linked recessive


What type of inheritance pattern does Huntington's disease show?

Autosomal dominant


Describe the mutation causing Huntington's disease

Caused by an increase in the number of CAG tandem repeats in the polyglutamine tract within exon 1 of the Huntington's disease (HD) gene on chromosome 4. Having more than 37 CAG tandem repeats can cause abnormal folding associated with HD


What is the molecular basis of dominance?

- dominance/recessiveness comes about via mutations in the genes
- most mutations are recessive (>90%)
- dominant mutations include:

Mutation in dosage sensitive gene:
1) reduced gene dosage (loss of function mutation in dose sensitive gene = haploinsufficiency)
2) increased gene dosage

Gain of function mutations:
1) altered mRNA expression
2) increased protein activity
3) toxic protein alterations
4) structural protein alterations
5) dominant negative effects
6) new protein function


What does imprinting mean?

Imprinting = silencing the gene
Leads to monoallelic gene expression (only one gene expressed because the other is silenced)

Maternal imprinted gene = maternal gene is silenced
Paternal imprinted gene = paternal gene is silenced

E.g. If a mutation is inherited maternally - no effect because the mutant allele has been silenced by imprinting (i.e. The maternal gene is switched off in the next generation)


How do clinical variations in monogenic diseases occur?

1) locus heterogeneity e.g. Autosomal dominant polycystic kidney disease has 2 target chromosomes and therefore 2 clinical variations in the disease - PKD1 (more severe) and PKD2 (less severe)
2) non genetic factors e.g. Autosomal dominant polycystic kidney disease severity is affected by hypertension, macrohematuria and renal tract infection status.
3) modifying influences from other genes
4) environmental factors


X linked recessive disorders affect:
Males only
Females only
Both genders equally?

Males only


X linked dominant disorders will affect:
Males only
Females only
Both genders equally?

Both genders equally


If a male has an x linked dominant disorder, who will be affected in the next generation?

Daughters (not sons - sons inherit Y from their fathers)

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