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M2M Unit II > Autosomal Recessive Disorders > Flashcards

Autosomal Recessive Disorders Flashcards

1
Q

Compound heterozygote

A

one who carries two different mutant alleles of the same gene.

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1
Q

Individuals with the Z/Z genotype have only ____ α1-AT activity and account for most cases of the disease.

A

10-15% of normal

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1
Q

ATD treatment?

A

delivering human SERPINA1 to the pulmonary epithelium

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2
Q

Most PKU cases are caused by defects in the _____ encoding phenylalanine hydroxylase.

A

PAH gene

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3
Q

ATD carrier frequency?

A

~1/25

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3
Q

____, relevant to ATD, is made in the liver and secreted into plasma.

A

α1-antitrypsin (ATT or SERPINA1)

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3
Q

The β subunit gene HEXB resides on chromosome ___.

A

5

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4
Q

Most PKU patients are ____ (i.e. having two different mutant alleles of the PAH gene).

A

compound heterozygotes

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4
Q

ATD

A

α1-Antitrypsin Deficiency

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5
Q

What is the frequency of T-S in the general population?

A

1/360,000

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6
Q

HexA is a heterodimer of ___, which are encoded by the HEXA and HEXB genes, respectively.

A

αβ

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7
Q

Phenylketonuria (PKU) phenotype

A

Microcephaly; possible profound mental retardation;. seizures, tremors, and gait disorders

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7
Q

Most ATD diseases are associated with two mutant alleles, the ___ and ___ alleles.

A

Z and S

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8
Q

findings in PKU: urine and sweat

A

High levels of phenylalanine metabolites and “mousy” odor

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8
Q

Elastase can destroy the connective tissue proteins (particularly elastin) of the lung, causing _____ and ______.

A

alveolar wall damage; emphysema

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9
Q

Other high-risk groups for T-S are ____, _____, and _____.

A

certain French-Canadian communities of Quebec, the Old Order Amish community in Pennsylvania, and the Cajun population of Louisiana

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11
Q

What does T-S disease destroy?

A

neurons in the brain and spinal cord

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11
Q

Although HexA is a ubiquitous enzyme, the impact of T-S is primarily in the ____ where most of GM2 ganglioside is synthesized.

A

brain

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12
Q

Allelic heterogeneity

A

the existence of multiple mutant alleles of a single gene

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13
Q

PKU carrier frequency

A

1/50

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13
Q

α1-antitrypsin (ATT or SERPINA1) is made in the ____ and secreted into ____.

A

liver; plasma

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15
Q

plasma findings in PKU

A

High phenylalanine and low tyrosine levels

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15
Q

What is the frequency of T-S in the Ashkenazic Jewish population?

A

1/3600

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16
Q

_____ patients have defects in both Hexosaminidase A and Hexosaminidase B (HexB).

A

Sandhoff disease

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18
Q

Sandhoff disease is caused by a defective ___ subunit; both ____ and ____ activities are affected.

A

β; HexA and HexB

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19
Q

Although HexA is a ubiquitous enzyme, the impact of T-S is primarily in the brain where most of _____ is synthesized.

A

GM2 ganglioside

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20
Q

high-risk group

A

a population with higher-than-expected risk for a particular AR disease

20
Q

_____ can destroy the connective tissue proteins (particularly elastin) of the lung, causing alveolar wall damage and emphysema.

A

Elastase

21
Q

Elastase can destroy the ______ , causing alveolar wall damage and emphysema

A

connective tissue proteins (particularly elastin) of the lung

23
Q

T-S

A

Tay-Sachs disease (GM2 gangliosidosis type I)

23
Q

Inability to degrade ______ results in up to 300-fold accumulation of this sphingolipid inside swollen lysosomes in neurons of the central nervous system.

A

GM2 ganglioside

25
Q

ATD disease frequency?

A

1/2,500

26
Q

The main target of _____ is elastase.

A

SERPINA1

28
Q

What is the cofactor of PAH?

A

BH4

29
Q

Elastase is released by _____ in the lung.

A

neutrophils

30
Q

ATD patients have a 20-fold increased risk of developing _____.

A

emphysema

30
Q

Defective _____ needed for metabolizing GM2 is responsible for T-S.

A

hexosaminidase A (HexA)

31
Q

Z/S compound heterozygotes have ____ α1-AT activity and may develop emphysema.

A

30-35 % of normal

33
Q

frequency of PKU

A

1/10,000 births

34
Q

______ is released by neutrophils in the lung.

A

Elastase

36
Q

_____ presents the same neurological symptoms as T-S.

A

Sandhoff disease (GM2 gangliosidosis type II)

37
Q

An eye abnormality called ____ is a characteristic of T-S

A

“cherry-red spot”

39
Q

The ____ in PKU damages the developing central nervous system in early childhood and interferes with the function of the mature brain

A

high phenylalanine level

41
Q

Individuals with ___ genotype have 50-60% of normal α1-AT activity and usually do not express disease symptoms.

A

S/S

41
Q

The most common mutant allele in T-S is _____.

A

a 4 bp insertion in exon 11 of HEXA

42
Q

Parental consanguinity

A

parents sharing one or more common ancestors.

43
Q

The α subunit gene HEXA resides on chromosome ___.

A

15

44
Q

In ATD, the ___ allele (Glu264Val) expresses an unstable protein that is less effective.

A

S

45
Q

The PAH gene encodes phenylalanine hydroxylase, a liver enzyme that catalyzes the conversion of ____ using molecular oxygen and a cofactor tetrahydrobiopterin (BH4).

A

Phe to Tyr

46
Q

In ATD, the ___ allele (Glu342Lys) encodes a misfolded protein that aggregates in the endoplasmic reticulum (ER) of liver cells, causing damage to the liver in addition to the lung.

A

Z

47
Q

The SERPINA1 gene is on chromosome ___.

A

14

49
Q

HexA and HexB refer to the two _____; HEXA and HEXB refer to two ____.

A

enzymes; genes

50
Q

___ compound heterozygotes have 30-35 % of normal α1-AT activity and may develop emphysema.

A

Z/S

52
Q

Why does smoking accelerate the onset of emphysema in ATD pts?

A

Tobacco smoke damages the lung– more neutrophils to the lung for protection– More neutrophils release more elastase– more severe lung damage

54
Q

Individuals with S/S genotype have ____ α1-AT activity and usually do not express disease symptoms.

A

50-60% of normal

55
Q

T-S is caused by a defective ___ subunit; only ___ activity is affected.

A

α; HexA

56
Q

The main target of SERPINA1 is _____.

A

elastase

57
Q

Which chromosome is the PAH gene located at?

A

12

58
Q

Many ATD patients also develop ____ and have an increased risk of ____ due to the accumulation of a misfolded α1-AT mutant protein in the liver.

A

liver cirrhosis; carcinoma

59
Q

Individuals with the ___ genotype have only 10-15% of normal α1-AT activity and account for most cases of the disease.

A

Z/Z

60
Q

What screening test is used for ATD?

A

Sequence specific oligonucleotide probes

62
Q

The PAH gene encodes ____, a liver enzyme that catalyzes the conversion of Phe to Tyr using molecular oxygen and a cofactor tetrahydrobiopterin (BH4).

A

phenylalanine hydroxylase

63
Q

Defective hexosaminidase A (HexA) needed for metabolizing ___ is responsible for T-S.

A

GM2

64
Q

PKU treatments?

A

1) low-phenylalanine diet 2) oral BH4, supplements

65
Q

Inability to degrade GM2 ganglioside results in up to 300-fold accumulation of this sphingolipid inside swollen _____ in neurons of the central nervous system.

A

lysosomes

66
Q

Hex B is a homodimer of ____.

A

ββ

M2M Unit II (21 decks)

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