Genetics Flashcards

Question

What is autosomal dominant inheritance?

Answer 1

* Affected individuals are **heterozygous for the mutation** * homozygous individuals often don't survive * **50% of inheritance** from one heterozygous parent * M= F affected

Answer 2

* Achondroplasia * Osteogenesis imperfecta * Neurofibromatosis type 1 * Marfan's syndrome * multiple epiphyseal dysplasia * mutliple hereditary exostoses

Answer 3

* Most common form of disporportionate rhizomelic dwarfism ( short limb) * inherited as complete penetrance * **87%** result of **new mutation** * gene encoding on chromosome 4, p16.3 * mutation affects **Fibroblast growth factor receptor 3 ( FGFR3)**

Answer 4

* A generalised disease of connective tissue due to a quantitative or qualitative defect of **type 1 collagen** * **Sillence classified** * **1-IV** * with subgroups in 1 and IV of **A /B** * where B = **dentinogenesis imperfecta** * **Autosomal dominant condition- cases from unaffected parents is _mosaicism_** * **pro-alpha 1 chain is encoded by COL1A1 gene on chromosome 17 and the pro-alpha 2 chain is encoded by COL1A2 gene on chromosome 7**

Answer 5

* Autosomal dominance * Complete penetrance but high variable expressivity * 50% of pts have a fresh gene mutation * gene encoded on chromosome 17 locus q11.2 * the gene encodes the protein **Neurofibromin** which acts as a tumour suppressor

Answer 6

* Mutation in fibrillin 1 gene * connective tissue disorder * arachnodactyly * scoliosis (50%) * protrusio acetabuli (15-25%) * ligamentous laxity * recurrent dislocations (patella, shoulder, fingers) * pes planovalgus nonorthopaedic conditions * cardiac abnormalities * aortic root dilatation * possible aortic dissection in future * mitral valve prolapse * superior lens dislocations (60%) * pectus excavatum * spontaneous pneumonthoraces * dural ectasia (\>60%) * meningocele

Answer 7

* **EXT 1 and EXt2 gene** * autosomal dominant * individuals with the EXT1 mutation have a more severe presentation compared to patients with the EXT2 mutation including * higher rate of chondrosarcoma 5-10% of transformation, proximal lesions more likely to undergo transformation than distal ones * more exostoses * more limb malalignment with less forearm and knee range of motion * more pelvic and flatbone involvement

Answer 8

* **Affected** individuals are **homozygous** for the genetic mutation * **Heterozgyous** individuals are **carriers** * 25% of producing an affected individual from 2 parent carriers * M= F affected * autosomal recessive conditions often produce errors of metabolism due to deficiency of specific enzymes

Answer 9

* **Mucopolysaccharidoses** ( except Hunters) * **Sickle cell anaemia** * **Diastrophic dysplasia**

Answer 10

* **Hurler syndrome** * mental retardation * disporportinate dwarfism * diaphyseal bordening of short misshapen boness * flaring of rib cage * widening medial end of clavicle * anterior wedging of verterbral bodies-\> kyphosis/ thoracolumbar gibbus * odontoid hypoplasia * **cloudy cornea** * caused by **alpha 1 iduronidase deficiency** * **Dermatan sulphate in urine** * **death in first decade of life**

Answer 11

* **Morquio** * **Type A= deficiency in galactosamine 6 sulphatase** * chromosome 16 q24.3 * **Type B= deficiency in beta -galactosidases** * chromosome 3 p21.33 * **Proportinate dwarfism** * _Normal mental IQ_ * _both need enzyme to break down glycoaminoglycans- esp keratan sulphate interferes with cartilage at growth plate_ * **Keratan sulphate in urine** * **type A more severe** * **both live into adulthood** * skeletal * **platyspondyly** * **ovoid vertebra & odontoid hypoplasia** * **flaring of rib cage** * **flattening of femoral heads** * **Genu valgum** * **Joint laxity**

Answer 12

**San filipio** * Multiple enzyme defiencies * Proportinate dwarfism * Mental retardation * **clear cornea** * Urine- **Heparan sulphate in urine** * **death in 2nd decade of life**

Answer 13

* Autosomal recessive of single gene leading to the subsitution of **glutamine for valine** at position **6** of the **beta-globulin chain of haemaglobin**

Answer 14

* Sulphate transporter * DTDST gene (SLC26A2) on chromosome 5 * failure of formation of the secondary centres of ossification ( epiphysis) * rhizomeliz dwarfism * hitcher's thumb * cauliflower ears * autosomal recessive

Answer 15

* **Cartilage oligomeric matrix protein (COMP)** or **type IX collagen** ( **COL9A2) ** * causes type 2 collagen dysfunction as type IX collagen acts as a link protein for type 2 collagen * **autosomal dominant** * **A form of dwarfism ( short limbed) characterized by irregular, delayed ossification at multiple epiphyses**

Answer 16

* Either sex affected * phenotype is dominant when a heterozygous female expresses the phenotype * 50% sons and 50% daughters risk inheritance from an affected mother

Answer 17

* **Hypophosphataemic rickets** * males express disease fully but females have expressivity in the heterozygous genotype * PEX ( cellular endopeptidases)

Answer 18

* **Phenotype is recessive** when expressed by a **homozygous female** * **All males are affected** * **Heterozygous females are carriers** * 25% of producing a normal male/female * an affected male transmits the affected gene thru all his daughters

Answer 19

* **Duchenne muscular dystrophy** * deficiency of protein **dystrophin ** * **Haemophilia A** * deficiency in **clotting factor VIII** * **Hunter's syndrome - mucopolysaccharidosis** * **sulpho-iduronate-sulphatase deficiency** * **-\> accumulation of dermatan and sulphate in urine** * **proportionate dwardfism** * **mental retardation** * **clear cornea**

Answer 20

* caused by abnormal synthesis of **Type II collagen** * **A form of short-trunk dwarfism caused by a defect in the secondary ossification center (epiphysis) ** * **mutation = COL2A1 on chromosome 12 ** * inheritance ``` * **autosomal dominant (SED congenita) X linked recessive (SED tarda) random mutation (50% of cases)** ```

Genetics Flashcards

(44 cards)