Lecture 17 - Mendelian Genetics Flashcards Preview

Unit 1 - Molecular and Cellular Principles of Medicine > Lecture 17 - Mendelian Genetics > Flashcards

Flashcards in Lecture 17 - Mendelian Genetics Deck (23):
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Autosomal recessive

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Autosomal recessive (or X-linked)

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Autosomal dominant

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Mitochondrial

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Locus heterogeneity

Same phenotype (disease) caused by mutations in different genes

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Allelic heterogeneity

Different mutations (alleles) in the same gene causing the same disease

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Clinical (phenotypic) heterogeneity

Different mutations in the same gene that lead to different diseases

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Do diseases work in an all-or-nothing fashion?

No! Many diseases work on contiuums (ex. cystic fibrosis)

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Dominance and recessiveness are properties of __________, not _______

Characters, not genes

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If the product from a heterozygote is not enough to cross threshold, the mutation is.....

Dominant!

 

If the reverse is true, it's recessive!

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Autosomal dominant Inheritance Criteria

  • Most affected individuals will be heterozygous
  • expressed every generation
  • Recurrence risk of 50%
  • Affected individuals usually have affected parents
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Autosomal recessive inheritance

  • Both parents of affected individuals to be carriers and asymptomatic
  • May appear as sporadic
  • Recurrence risk is 1 in 4
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Compound heterozygote?

An organism is a compound heterozygote if it has two recessive alleles for the same gene, but with those two alleles being different from each other (for example, both alleles might be mutated but at different locations). Compound heterozygosity reflects the diversity of the mutation base for many autosomal recessive genetic disorders; mutations in most disease-causing genes have arisen many times. 

 

ex. cystic fibrosis

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After birth and not affected by autosomal recessive disease, what is the chance a brother or sister of an affected individual have of being a carrier?

2/3

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Describe the chances of parents, grandparents, uncles, and cousins being carriers...

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X-linked recessive inheritance

  • Usually males affected (unless an affected male marries a carrier female, or extreme X-inactivation)
  • All daughters of affected males are carriers
  • Half the sons of carrier females are affected
  • No male to male transmission
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Haldane's Law

???? look up!

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X-linked dominant

  • RARE
  • Affected males have normal sons and affected daughters
  • Twice as many affected females as males
  • Most affected females will be heterozygous, so offspring will be affected
  • Usually more sever/lethal in males

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Y linked

No/few known Y linked diseases

Only males would be affected

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Mitochondrial inheritance

Trait appears to be inherited exclusively through females

All offspring of affected females will probably be affected

Highly mutatable compared to nuclear DNA

 

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New Mutation

Disease will appear sporadic but will be familial in descendents of affected individuals but not in earlier generations

Mitochondria have high mutation rate

Estimate of 100-200 new bp changes in each person

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Mosaic

Germline or somatic

Tissue has two or more cell lines of different genotype (derived from single zygote)

ex. lymphoma or leukemia

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Chimeras

Individuals derived from cells of two different zygotes

Ex. recipient would be bone marrow transplant from donor

Or absordbing twin in utero