6093054
Description
Flashcards by Emma Allde, updated more than 1 year ago
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Created by Emma Allde
over 8 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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