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Semester 5 FSNM Exam 9 > Genetics 1 > Flashcards

Genetics 1 Flashcards

1
Q

Mutations effect all kinds of proteins - name them

A

1 Enzymes
2 Proteins involved in transport and storage
3 Structural proteins
4 Proteins involved in growth, differentiation and development
5 Receptor and signaling proteins

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2
Q

Which proteins present with a recessive mode of inheritance

A

Enzymes

Transport and storage proteins

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3
Q

Which proteins present with a dominant mode of inheritance

A

Structural proteins
Proteins involved in growth, differentiation and development
Receptor and signaling proteins

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4
Q

Protein defects vary in severity - what three things could happen

A

Null mutation
Loss of function
Gain in function

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5
Q

Protein defects vary in severity - what three things could happen - null mutation

A

The underlying mutation might completely destroy a protein

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6
Q

Protein defects vary in severity - what three things could happen - loss of function

A

The mutation may reduce the protein’s activity

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7
Q

Protein defects vary in severity - what three things could happen - gain in function

A

The mutation may alter the proteins activity, even convey a new function

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8
Q

Single gene defects show what type of inheritance

A 
Four Mendelian models
1 Autosomal dominant
2 Autosomal recessive
3 X linked dominant
4 X linked recessive 
OR - Mitochondrial inheritance (that doesn't follow Mendelian rules)
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9
Q

Single gene defects - Recessive disorders cause disease in what state

A

Homozygous

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10
Q

Dominant disorders cause disease in what state

A

Heterozygous

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11
Q

Single gene defects - Mendelian rules of inheritance - With one heterozygous and one homozygous parent - expect what for a typical dominant allele

A

50% of the children will be impacted by the disorder in the heterozygous state (Aa)

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12
Q

Single gene defects - Mendelian rules of inheritance - With both parents heterozygous - expect what for a typical recessive allele

A

25% will get a recessive allele in the homozygous state (aa)

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13
Q

Mendelian rules - recurrence and occurrence risk

A

They are the same!

So every child that you have has the same risk

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14
Q

Single Gene - Recessive Inheritance

A

One normal allele is enough to prevent disease because a loss in gene dosage can be compensated

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15
Q

Single gene - recessive inheritance - why is one normal allele enough to prevent disease

A

Loss in a gene dosage can be compensated for - enzymes are highly regulated and so they will adjust to the metabolic situation

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16
Q

Single gene - dominant inheritance

A

Disease will still show in heterozygous state

Many different models to explain dominant inheritance

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17
Q

Single gene - dominant inheritance - why does disease show in heterozygous state for proteins involved in growth, differentiation, and development

A

Critical in gene dosage because their activity is not regulated

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18
Q

Single gene - dominant inheritance - why does disease show in heterozygous state for receptor and signaling proteins

A

Esp. those with a gain in function

Because signal is like an alarm so if you have 25, even if just 1 goes off, there is a response

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19
Q

Single gene - dominant inheritance - why does disease show in heterozygous state for structural proteins

A

(ex cytoskeletal or skeletal proteins)
Subunits need to fit just right to form the macromolecular structure so if just one is off, the entire structure does not come together or assemble well

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20
Q

Single gene - causes for dominant inheritance

A

Haploinsufficiency
Dominant negative effect
Gain in function mutation
Lack of back up (two hit model)

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21
Q

Single gene - causes for dominant inheritance - Haploinsufficiency

A

In the haploid state, you are not making enough proteins - ex of hgb where you need a lot and even though you have one healthy in the heterozygous state, it can’t ramp up enough to meet needs so you end up with an insufficiency

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22
Q

Single gene - causes for dominant inheritance - Dominant negative effect

A

Protein that hangs around and just by being there has a negative effect on the other proteins
Impacts mostly structural proteins

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23
Q

Single gene - causes for dominant inheritance - Gain in function mutation

A

Receptor that triggers a signal transduction cascade even in the absence of ligand
Impacts mostly signal transduction proteins

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24
Q

Single gene - causes for dominant inheritance - Lack of backup (two hit model)

A

Explains a lot of CA hereditary syndromes
There are specific alleles that are supposed to stop cell division at certain times but with heterozygous one of your brakes is already defective and puts you at a higher risk

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25
Q

Single gene - X linked inheritance

A

M - one X
F - two X but one is inactivated
Fathers pass X to daughters, Y to sons
Y initiates M development

26
Q

Single gene - X linked inheritance - if father has a mutation on X

A

it will not be passed to son but will always be passed to daughter

27
Q

Single gene - X linked inheritance - X chromosome inactivation

A

Every cell has to decide which X to inactivate and say half inactivate one X and half inactivate the other - F are mosaic - if it is a true recessive disorder, F won’t show the disorder (it is in the heterozygous state)

28
Q

Single gene - X linked inheritance - example of a severe X linked disorder

A

Muscular dystrophy - M die early in life, F are able to live normally though because half of their cells are still ok and able to regenerate

29
Q

Single gene - Mitochondrial Inheritance

A

Does not follow Mendelian rules
Mitochondria come from ovum and are inherited only from mother
Cells have many mitochondria with many copies of the chromosome - Variable expression of mutant phenotype

30
Q

Single gene - mitochondrial inheritance - what cells are impacted the most

A

Those that consume the most energy
Like optic nerve
Can lead to muscle deterioration and blindness

31
Q

Single Gene - example of autosomal recessive diseases

A

PKU (an enzyme defect)

CF (defective transporter)

32
Q

Single Gene - example of autosomal dominant diseases

A

Neurofibromatosis
Huntingon Disease
Achondroplasia
Collagen disorders

33
Q

Single gene - autosomal recessive diseases - characteristics of an autosomal recessive pedigree

A

Affected children usually have normal parents
Both sexes are equally affected
Consanguinity increases risk
Both parents hetero so risk for child to get disease in homozygous state is 25%

34
Q

Single gene - autosomal recessive diseases - characteristics of an autosomal recessive pedigree - Consanguineous matings

A

If you see a child from a consanquineous marriage - it is likely a recessive disorder
Their chances of having the mutant allele is higher than what you would expect from random mating

35
Q

Single Gene - example of autosomal recessive diseases - PKU - what is it

A

Cause by a defect in phenylalaning hydroxylase (PAH)
Phenylalanine accumulates and damages the developing CNS
Early dietary intervention is key

36
Q

Single Gene - example of autosomal recessive diseases - PKU - how common and tx

A

One of many inborn errors of metabolism
Rare, but more common of the rare ones
Tx is effective in preventing mental retardation
Heel prick soon after birth for blood analysis

37
Q

Single gene - characteristics of autosomal dominant pedigree

A

An affected child has at least one affected parent
Both sexes are equally affected
Disease can be transmitted from father to son
Often homozygotes are more severely affected than heterozygotes

38
Q

Single Gene - example of autosomal dominant diseases - Neurofibromatosis Type 1 (NF1) - what is it

A

Rare neuro disorder

Caused by defect in neurofibromin gene (large gene - big target)

39
Q

Single Gene - example of autosomal dominant diseases - Neurofibromatosis Type 1 (NF1) - What are they symptoms

A

Multiple benign tumors in skin
Benign tumors in iris of they eye (hamartomas or Lisch nordules)
Pigmented skin (cafe au lait)
Tumors of CNS, mental retardation

40
Q

Single Gene - example of autosomal dominant diseases - Neurofibromatosis Type 1 (NF1) - Expressivity

A

Variable expressivity

Same mutation but a wide spectrum of what it can cause and no telling how it will present in following generations

41
Q

Single Gene - example of autosomal dominant diseases - Neurofibromatosis Type 1 (NF1) - Penetrance

A

All or nothing concept
The % of people with the disease gene who develop symptoms
NF1 has 100% complete penetrance - every carrier will express symptoms

42
Q

Single Gene - example of autosomal dominant diseases - Huntington Disease - what is it

A

Neurodegenerative disorder with late onset
Very rare
Caused by gain in function mutation in the huntington gene
Triplet expansion in gene causes protein instability

43
Q

Single Gene - example of autosomal dominant diseases - Huntington Disease - how does it happen

A

Repeat of CAG sequence and around 40 repeats it is pretty much a given that the person will develop HD
People hang out on bubble though and when they have kids, the repeat number increases
Once the gene has been switched from pre mutation to full mutation (around 40) the gene will be passed on in a dominant manner

44
Q

Single Gene - example of autosomal dominant diseases - Huntington Disease - anticipation

A

The severity of the disease increases when transmitted through a pedigree - this is frequently observed in triplet expansion mutations and is referred to as anticipation

45
Q

Single Gene - example of autosomal dominant diseases - Achondroplasia - what is it

A

Most frequent form of dwarfism

Cause by a defect in a fibroblast growth factor receptor (FGFR3)

46
Q

Single Gene - example of autosomal dominant diseases - Achondroplasia - what type of mutation

A

Gain in function mutation - receptor is constitutively active - dominant negative effect
Inhibition of bone growth leads to short stature
Illustrates importance of new mutations in autosomal dominant diseases

47
Q

Single gene - reduced fitness and new mutations

A

Often an allele carrier has a reduced chance of reproduction (reduced fitness)
Reduced fitness makes the mutant allele disappear from population BUT allele frequencies stay constant because new mutations appear and compensate for the loss of mutant alleles

48
Q

Single gene - Genetic heterogeneity of collagen disorders - what are the two types of heterogeneity

A

Allele heterogeneity

Locus heterogeneity

49
Q

Single gene - Genetic heterogeneity of collagen disorders - what are the two types of heterogeneity - Allele heterogeneity

A

Different mutations in the same gene have different phenotypes

50
Q

Single gene - Genetic heterogeneity of collagen disorders - what are the two types of heterogeneity - Locus heterogeneity

A

Mutations in different genes have the same phenotype

51
Q

Single gene - Allele heterogeneity example

A

Some types can be explained by haploid insufficiency and other by dominant negative effect
So same gene but different mutations and different phenotypes

52
Q

Single gene - X linked recessive main features

A

No father-son transmission
Affected boys usually have unaffected parents
M affected more than F (because they don’t have back up)
Seems to skip generations by transmission through carrier females

53
Q

Single gene - X linked recessive examples

A

Duchenne and Beck MM dystrophies

54
Q

Single gene - X linked recessive - mm dystrophy - how common - what is it

A

Rare
Defect in dystrophin leads to mm damage
Dystrophin is large target
Low fitness of affected M - disease if often due to new mutations

55
Q

Single gene - X linked recessive - mm dystrophy - Recurrence risk

A

Low because disease is often due to new mutations and chance that second child also gets random new mutation is low

56
Q

Single gene - X linked recessive - mm dystrophy - Dystrophin staining

A

Carrier females are mosaics - even though they are just a carrier, it does not look 100% normal, you can see that some cells activated the defective cell so they look abnormal but the half that activated the healthy one look normal

57
Q

Single gene - X linked dominant

A 
Very rare
No father son transmission 
All daughters of affected father are affected
Females more frequently affected
Often lethal in males
58
Q

Single gene - Mitochondrial inheritance - how passed

A

Passed from mothers to all children
Fathers to nobody
Most are caused by a nuclear mutation but then are passed in a Mandelian mode
Mitochondrial DNA is present in multiple copies

59
Q

Single Gene - Mitochondrial inheritance - a patient with a mitochondrial disorder has cells with

A

varying fractions of defective mitochondrial DNA molecules (heteroplasmy)

60
Q

Single Gene - Mitochondrial Inheritance - example

A

Leber’s Hereditary Optic Neuropathy (LHON)

61
Q

Single Gene - Mitochondrial inheritance - LHON

A

Most prevalent of the mitochondrial disorders
Caused mostly by a mutation in the ND1 gene
Leads to rapid deterioration of the optic nerve

Semester 5 FSNM Exam 9 (4 decks)

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