Th2L03 Monogenic disorders


Medicine Y1 (Theme 2 | Genetics) Flashcards on Th2L03 Monogenic disorders, created by Emma Allde on 22/08/2016.
Emma Allde
Flashcards by Emma Allde, updated more than 1 year ago
Emma Allde
Created by Emma Allde over 7 years ago

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Question Answer
What are monogenic disorders Diseases caused by single locus changes
What are the characterstics of an autosomal recessive trait (6) • Rare in pedigree • Often skips generations • Hidden in heterozygous carriers • Affects males and females equally • Transmitted by either sex • Frequency of carries can vary
What explains why autosomal recessive disorders pervail Heterozygote must confer a selective advantage
What are the characterstics of an autosomal dominant trait (5) • One dominant allele is sufficient for diseases to be carried on to next generation • 50% chance of developing disorder with just one mutant allele • Fequent in pedigree • Persons are affected in each generation Affects both genders equally and is transmitted by both genders equally
What is a lethal allele Alleles that cause an organism to die only when present in homozygous condition
What is genetic anticipation Where the condition becomes more severe (or appears earlier) in successive generations
In what commonly studied AD disease is genetic anticipation seen Huntington's disease
What explains genetic anticipation meitotic instability
What are the characterstics of an X-linked recessive trait (4) • Gene present on the X chromosome exhibit unique patterns of inheritance in comparison with autosomal genes (because males inherit their X from their moth) • Will occur more frequently in males • All daughters of affected fathers are carries Cannot be passed from father to son
What is cystic fibrosis genetic disorder that occurs in people with two copies of a certain recessive allele
What is the main characteristic of cystic fibrosis excessive secretion of mucus and consequent vulnerability to infection
What gene is implicated in cystic fibrosis CFTR on chromosome 7
What is the CFTR on chromosome 7 gene code for Cystic fibrosis transmembrane conductance regulator gene
What is the Cystic fibrosis transmembrane conductance regulator gene responsible for: (3) Helps create sweat, digestive juices and mucus Pumps Cl- out of cells (chloride channel on the cell membrane) leading to water existing the cell via osmosis Maintains a free flowing mucus layer outside of the cell (vital in e.g. alveoli)
What allele is this: C (on chromosome 7) Normal wild-type allele encodes for functional CFTR (Dominant)
What allele is this: c (on chromosome 7) Mutant allele lacking 508th codon; (Recessive)
How many mutant alleles are implicated in cystic fibrosis Over 500 but CFTRΔ508 is the most common in N. Europe (70-80% of mutant alleles, (1 in 25))
What are the charactertics and result of mutant CFTRΔ508 (4 steps) Does not exit the endoplasmic reticulum Never ends up in the Golgi complex Results in loss of Cl- gradients Mucus becomes thicker, leads to lung infections, blockage of ducts in pancreas and intestine
What is the selective advantage of CF heterozygote remains unknown
How old is the mutant CF gene over 52,000 years
What is the lifespan of an individual with CF ca. 50% reach 40th birthday
Where is Sickle cell anaemia most common parts of Africa and in people of African origins
What are the rates of sickle cell anaemia in malaria-endemic regions 1 in 3
What is the advantage of the Sickle cell heterozygote (HbA/HbS) Less likely to die from malaria (reproduction of the parasite is limited in heterozygote as RBCs rupture prematurely)
What is Huntington's disease An autosomal dominant, hereditary disease marked by degeneration of the brain cells and causing chorea and progressive dementia
What mutation is responsible for Huntington's disease mutations at HD locus, specifically in the terms of pathogeni repeat expansion of the CAG codon
How many CAG repeats at the HD locus is normal approx. 28
How many CAG repeats at the HD locus is pathogenic 36+
What is the result of 36+ CAG repeats at the HD locus aggregation of protein, cytotoxicity, then neuronal cell death
What is the main characteristic of Myotonic dystrophy wasting of muscles
What causes myotonic dystrophy autosomal dominant inheritance of OR de novo triplet expansion of CTG repeats
What is achondroplasia An autosomal dominant genetic disorder that results in a form of dwarfism
When is achondroplasia dangerous Can be deadly perinatally when homozygous (lethal allele)
What causes achondroplasia mutation in fibroblast growth factor receptor 3 in chromosome 4
What haemophilia A an inherited bleeding disorder that is mostly just expressed in males and involves defects in factor VIII leading to haemarthrosis and muscle haemorrhages
What is haemarthrosis bleeding into joint spaces
What is Factor VIII Gene for blood clotting on X chromosome
What is the X-linked recessive probability (of an affected female) in Haemophilia A Half the sons of a carriers will be affected; half the daughters will be carriers
What causes red-green colour blindness X-linked recessive trait Results in lack of specialised retinal cells
How common in red green colour blindness in males 800 per 10K males
What is Duchenne muscular dystrophy A human genetic disease caused by a sex-linked recessive allele characterised by progressive weakening and a loss of muscle tissue
How common is Duchenne muscular dystrophy 3 per 10K males
What causes Duchenne muscular dystrophy deletion of DNA segment
What is X-linked ichthyosis An X-linked recessive condition affecting males Pt will have large scales that appear brown in colour This condition spares the palms and soles
How common is X-linked ichthyosis 2 out of 10K males
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