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G and H > Autosomal Recessive > Flashcards

Autosomal Recessive Flashcards

week 5

1
Q

What are the three main types of autosomal recessive disorders? What are the respective examples?

A

Cell metabolsim - PKU
Blood Cell function - Thalassemia, Sickle Cell, Haemochromatosis,
Membrane function- cystic fibrosis

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2
Q

What are compound heterozygotes?

A

individual with 2 different alleles (both defective)

severity depends on how much residual function is retained

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3
Q

Heterozygote advantage

A

relatively high frequency of disease-associated alleles causing reduced fitness for homozygotes = heterozygotes have a greater fitness

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4
Q

Features of autosomal recessive inheritance

A

single generation
parents and children of affeced = normally unaffected
male and female equally affected
parents = carriers

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5
Q

What is the recurrence risk for 2 carrier parents?

A

1/4

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6
Q

What is the chance that an unaffected sibling of affected individual is a carrier?

A

2/3

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7
Q

What is the impact of consanguineous marriage on autosomal recessive inheritance?

A

affected individuals seen in several generations.

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8
Q

What is gene therapy?

A

use of DNA as a pharmaceutical agent to treat lectures.

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9
Q

How does somatic cell gene therapy work?

A

replace defective genes in somatic cells so cells can produce the missing product or eliminate/ alleviate symptoms

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10
Q

What is germline gene therapy?

A

corrections are made to the germ cells such that inheritable genetic alterations are removed.

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11
Q

How can genes be introduced to somatic cells?

A

Mechanical (liposomes or microprojectiles) or Viral vectors

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12
Q

What are the 3 approaches to get genes to right site?

A

Ex vivo - target cell removed, cultured in lab, re-inserted

in situ- affected tissue directly exposed to therapy vector(not great for CF)

In Vivo- vector introduced t body, vector homes in on cells specifically designed for (best for CF)

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13
Q

How can an Autosomal receivve child be produced from parents with inly 1 carrier?

A

Germline mosaicism

de novo during embryogenesis

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14
Q

What is the affected gene and mutation for PKU?

A

Affected gene
- PAH gene
Mutation
-p.Arg408Trp

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15
Q

Clinical features of PKU including: early sympotims in 50% of untreated infants, nervous dysfunctions and common features of untreated individuals.

A

Early symptoms
-vomiting
-irritability
-eczema -like rash
-mousy urine odor

Nervous dysfunction
-increased muscle tone
-more active tendon reflexes

Untreated symptoms
-microcephaly
- widely spaced teeth
-prominent cheek and upper jaw bones

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16
Q

What is the screening test for PKU?

A

Heel prick test

Assess Phenylalanine (p) levels

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17
Q

Treatment of PKU?

A

Maintenance of blood P levels

Avoiding high-protein foods

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18
Q

Quality of life for PKU?

A

normal life and life span if following treatment

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19
Q

What gene is affected for a-thalassemia?

A

HBA1/2

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20
Q

What is the gene affted for b-thalassemia?

A

HBB

21
Q

What is the phenotypic mechanism of a and b thalassemia?

A

incorrect or no synthesis of hemoglobin globin chains
a- a globin chain
b- b globin chain

22
Q

What is the normal structure of hemoglobin and where are the genes located for a and b globin?

A

Normal: tetramer of 2-a-like and 2-b-like globin subunits. subunits change t fit needs of embryo, fetus and adult.

A: 4-a genes = 2 on each copy of Ch16
B: 2-b genes = 1 on each Ch11

23
Q

What are the different types of a-thalassemia? Summarise each

A

silent
1 of 4 a mutated and asymptomatic
-minor
2 of 4 mutated = mild anaemia
-HbH
-3 of 4 mutated = mild -moderate anemia, enlarged spleen and jaundice
Hb Barts
-4 of 4 mutated = severe -excess fluid build up in developing baby = not survive after birth (usually

24
Q

What are the different types of b-thalassemia? Summarise each

A

Minor
-1 of 2 mutated = lifelong mild anaemia
Intermediate
-2 of 2 mutated = mild/mod anameia, slow growth, symptoms early childhood or later
Major
2 of 2 = life-threatening anemia in first year, jaundice, enlarged spleen, bone changes and developmental delay.

25
Q

Treatment of Major b-thalassemia.

A

Major B
-bone marrow transplant, cord blood transplantation and regular transfusions.

26
Q

Treatment of Intermediate b-thalassemia.

A

splenectomy, sporadic blood transfusion and folic acid supplementation and iron chelation

27
Q

Treatment of HbH (a-thalassemia)

A

transfusion may needed during a hemolytic or aplastic crisis

28
Q

How is Thalassemia screened for?

A

Hematological testing of RBC
-peripheral blood smear
-supravital stain to detect RBC inclusion bodies
-electrophoresis

29
Q

What is the diagnostic test for thalassemia?

A

molecular genetic testing of HBA1/2 and HBB

30
Q

How may gene therapy be used to treat thalassemia?

A

haemoglobin switching (place y and a in place of defective b

31
Q

Life expectancy of major-b-thalassemia.

A

major= delayed due to switching of y-b subunits in infancy, usually die between 3-6 months.

32
Q

Affected gene and mutation of Sickle Cell anaemia.

A

Gene
HbA = HbS
Mutation
Non-conservative
DNA: CTC = CAC
RNA: GAG = GUG

33
Q

Describe the phenotypic change in sickle cell anemia.

A

Changed fiber formation of RBC = distorted RBC shape

34
Q

Screening for sickle cell anemia

A

Blood screening for deformed erythrocytes

Electrophoresis

Heel prick test of newborn

35
Q

Describe the management of sickle cell anameia.

A

Based on crisis prevention
-drink plenty of fluids
-pain med
-blood transfusions

36
Q

Affected gene and mutation of Haemochromatosis.

A

Gene
HFE gene

Mutation
P.Cys282Tyr or P.His63Asp

37
Q

Explain the consequential phenotypic mechanism of Haemochromatosis.

A

Mutant HFE not bind properly to transferrin receptor which regulates Hepcidin (iron regulation)

38
Q

Clinical features of Haemochromatosis.

A

impacts the ability to absorb all protein-associated protein from food and is instead stored in tissues

Joint pain
Fatigue
Bronze pigment
Abdominal pain
decreased libido

39
Q

What is the age of onset for Haemochromatosis symptoms?

A

females
-symptoms present 30-50yrs old
(due to removal of iron in menstruation)
Males
-less than 50

40
Q

Screening test for Haemochromatosis.

A

Iron content in blood or liver.

41
Q

What is the treatment for haemochromatosis?

A

regular phlebotomy (blood enzyme tests)

42
Q

Affected gene and mutation of CF.

A

Affected gene
-CFTR
Mutation
-p.Phe508del (misfolded protein does not migrate to cell membrane)

43
Q

Clinical features of CF in terms of pancreas, lungs, Repro ducts and sweat galnds.

A

Pancreas
-blocked glands = cyst formation = fibrous
-decreased fat digestive enzymes = undernourishment

Lungs
-mucus thicker = persistent cough and lung infections

Reproductive ducts
-ductus deferens blocked = infertility

Sweat glands
-no-re-uptake of secreted salt = salty skin and body in salt

44
Q

Is there a higher carrier or affected individual incidence of CF in Australia?

A

Carriers

Carriers:
1/25

Affected:
1/2500 babies (1 per 4 yrs)

45
Q

Screening tests for CF.

A

Heel prick test – assesses pancreatic IRT

12-panel mutation screen for carriers

46
Q

What is the diagnostic test for CF?

A

Diagnosis
Sweat chloride test

47
Q

Medications and gene therpy for CF.

A

Medications
-antibiotics, mucous thinning drugs, bronchodilators (open airways)

Gene therapy (in Vivo is best)
Potentiators
-binds to CFTR channels and aid opening
Correctors
Helps correct processing of CFTR channel proteins

48
Q

Treatment and lifestyle changes for CF

A

Organ transplant, chest therapy, pulmonary rehab, nebulizers every morning and night, psychological counselling and nutrition and exercise.

G and H (16 decks)

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