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Enzymes > Single gene disorders > Flashcards

Single gene disorders Flashcards

1
Q

Recessive inheritance is mostly observed in defects of what?

A

Enzymes

Proteins involved in transport and storage

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2
Q

Dominant inheritance is mostly observed in defects of what?

A

Structural proteins
Proteins involved in growth
Receptor and signalling proteins

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3
Q

What is haploinsufficiency?

A

When half of gene cannot carry out cell function (explanation of dominant mode of inheritance)

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4
Q

What is the dominant negative effect?

A

When mutational protein competes with normal form, or destabilizes a structure composed of normal and mutated (explanation of dominant mode of inheritance)

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5
Q

What is the gain of function explanation for dominant inheritance?

A

Change in the function of the mutated protein compared to normal (signal proteins usually)

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6
Q

What is the lack of back up explanation of dominant inheritance?

A

Like two-hit model of CA

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7
Q

What is the psuedoanasomal region of Y?

A

Part of the Y chromosome that is similar to X

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8
Q

True or false: the X chromosomes in females are both expressed simultaneously by each cell

A

False–each cell expresses one, but varies between cells

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9
Q

What is the coefficient of inbreeding?

A

Describes the degree of homozygosity of a child

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10
Q

What is the most prevalent IEM?

A

PKU–defect in F hydroxylase

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11
Q

What recessive disease (that we discussed) is characterized by a defective Cl transporter?

A

Cystic fibrosis

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12
Q

Why is the sweat of someone with cystic fibrosis salty/more electrically conductive?

A

Loss of Cl transporter and effects on Na transporter

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13
Q

What are the two major types of cystic fibrosis discussed?

A

Pancreatic sufficient

Pancreatic insufficient

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14
Q

What are two possible explanations as to why there is heterogenity in cystic fibrosis?

A
  1. Different allele mutations

2. Modification of other proteins (different ion channel may take over)

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15
Q

Why aren’t patient found with homozygous dominant alleles of a disease?

A

This is usually fatal

also less probable

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16
Q

What is the term that describes when someone who has a mutated genotype does not express the phenotype?

A

incomplete penetrance

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17
Q

What accounts for the “skip” in generations seen in inherited diseases?

A

incomplete penetrance

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18
Q

What is the term that describes how strong a phenotype shows?

A

Expressivity

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19
Q

NF1 has highly variable expressivity. What does this mean?

A

The symptoms expressed by individuals with the disorder vary widely

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20
Q

NF1 has complete penetrance. What does this mean?

A

ALL individuals with NF1 will express some sort of symptoms at some point

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21
Q

Why is examining the parents crucial in determining if their next child (after having one who is affected) will be affected with a disease?

A

To determine whether the parents are carriers with overlooked symptoms, or if the mutation in the child is new.

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22
Q

True or false: if a parent has an inherited disease, but has only mild expression of it, then his/her affected offspring will also have mild expression

A

False

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23
Q

What is the cause of Huntington’s disease?

A

Triplet expansion of a CAG triplet leading to the expansion of polyglutamine stretches

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24
Q

What is the number of CAG repeats in a normal individual? In someone with huntingons?

A

9-35 is normal

>40 huntingtons

25
Q

What is a premutation?

A

A propensity to transmit a mutation to one’s offspring without carrying the disease–Huntington’s is the classic example (note this is NOT a recessive gene)

26
Q

What is the term describing the increasing severity of a disease as it is transmitted through a pedigree?

A

Anticipation

27
Q

What is the gene that is the cause of Achomdroplasia?

A

FGFR3

28
Q

What is FGFR3?

A

A Y-kinase that inhibits chondrocyte proliferation

29
Q

What is a mutational hotspot?

A

An area where new mutations form readily

30
Q

Why are older male sperm more likely to produced offspring with genetic mutations?

A

Higher chance of developing spontaneous mutations since they are produced from cells that have had a longer time to mutate

31
Q

What are the two ways collagen defects can develop

A
  1. Problem with the primary structure of collagen

2. Problem with the enzymes that make collagen

32
Q

The dominant form of Ehlers-Danlos syndrome is due to what?

A

Mutation in collagen

33
Q

The recessive form of Ehlers-Danlos syndrome is due to what?

A

Mutation in enzymes that process collagen

34
Q

Familial hypercholestremia is a recessive or dominant disorder?

A

Dominant

35
Q

How does Familial hypercholestremia demonstrate the gene dosage effect?

A

Homozygotes have 4x higher LDL levels–heterozygotes have only x2

36
Q

What are the surface regions that LDL receptors are found in?

A

coated pits

37
Q

What is the protein that LDL receptor binds to?

A

Apoprotein B

38
Q

The LDL receptors are internalized and are turned into what structure?

A

Lysosomes

39
Q

What happens to the LDL receptor when it is in the lysosome?

A

Bud off into vesicles to be recycled back to cell surface

40
Q

What is the action of acyl-coa:cholesteryl acyltransferase?

A

Esterifies excess cholesterol that is released by the LDL receptor lysosomes

41
Q

Why is it notable that the LDL receptor is a heavily glycosylated protein?

A

Room for error in glycosylation

42
Q

What is the RET gene’s function?

A

Receptor and signalling molecule in development

43
Q

What are the two types of mutation that the RET protein can undergo?

A

gain-of-function (increased signal)

Loss-of-function (loss of signal)

44
Q

A LOF in the RET protein leads to what disease?

A

Hirschsprung disease (impairment of neuron development)

45
Q

A GOF in the RET portein leads to what disease?

A

Multiple endocrine neoplasia (proliferation of neuroendocrine cells)

46
Q

Why are both Hirschsprung disease and MEN dominant diseases?

A

Hapaloinsufficiency

47
Q

What is Duchenne muscular dystrophy?

A

Defect in the dystrophin gene

48
Q

What does dystrophin do?

A

it is a protein that is essential for attachment of muscle cells to the ECM

49
Q

What type of inheritance is DMD?

A

X-linked recessive

50
Q

True or false: the mutational rate of mitochondrial DNA is much lower than the nuclear DNA

A

False

51
Q

What is heteroplasmy?

A

cells contain varying fractions of defective mtDNA (due to the fact that there is >1000 mtDNA in a cell)

52
Q

What is LHON?

A

Mutation in the ND1 gene the encodes complex I of the ETC

53
Q

What is a compound heterozygote?

A

When an individual has two mutant alleles

54
Q

What is allele heterogeneity?

A

different mutations in the same gene causing different phenotypes

55
Q

What is locus heterogeneity?

A

Mutations in different genes cause the same phenotype

56
Q

What are modifier genes?

A

Genes specific to an individual that modify a mutated gene’s effects

57
Q

What is pleiotrophy?

A

A mutation that causes multiple phenotypes–not all carriers of same mutation display the same phenotype

58
Q

What type of mutations do ova contribute?

A

non-disjunction

59
Q

What type of mutations do sperm contribute?

A

Replication errors

Enzymes (24 decks)

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