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SP 16 - Path Test 2 > Genetic Diseases > Flashcards

Genetic Diseases Flashcards

1
Q

How many Chromosomes do humans have?

A

22 pairs of autosomes
1 pair of sex chromosomes
46 total

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2
Q

Alterations in the genetic code are termed what?

A

Mutations

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3
Q

What is it called when one chromosome in the pair is effected?

A

Heterozygous

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4
Q

What is it called when both chromosomes in the pair are effected?

A

Homozygous

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5
Q

Mutations affecting somatic cells

A

May result in tumors or developmental malformations

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6
Q

Mutations affecting germ cells

A

Can be inherited

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7
Q

What are the different types of mutations?

A

Point mutations
Frameshift
Trinucleotide repeat

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8
Q

Point mutations

A

Single base mutation

Ex: Sickle Cell Anemia

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9
Q

Frameshift

A

There is an insertion or deletion of 1-2 base pairs, which can cause alterations/shifts in reading or early stoppage

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10
Q

Trinucleotide repeat

A

An amplification of a 3-nucleotide sequence

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11
Q

What are the different types of polymorphisms?

A

Single nucleotide polymorphism

Copy Number Variations

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12
Q

Single nucleotide polymorphism

A

Variation in just one nucleotide at at a single site on the DNA molecule
May not cause disease by themselves, but can be precursors for multigene diseases such as diabetes or hypertension

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13
Q

Copy number variation

A

A particular gene that varies from one individual to the next
Different numbers of large continuous stretches of DNA

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14
Q

Epigenetic Changes

A

Modulation of gene expression without altering the DNA sequence
-usually chemical modifications

Methylation of promoter regions make them inaccessible to RNA polymerase - reducing the expression

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15
Q

Alterations to Non-coding RNAs

A

micro-RNAs (mRNA) inhibit translation of their target messenger RNA into their corresponding proteins
-they can come in and silence tumor suppressor elements

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16
Q

Diseases caused by Single gene defects

A

Genetic alterations often results in the production of an abnormal protein, which can alter the phenotype

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17
Q

T/F - a mutation has to occur at the same basepair in order to cause the same phenotypic alteration

A

False - because genes are comprised of many base pairs, a mutation can occur t different places within the gene, yet produce essentially the same phenotypic alteration

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18
Q

Autosomal Dominant Disorders

A

Mutated gene can be on one of the autosomes and the disease will be clinically evident
Delayed onset - even though the mutant gene is present form birth

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19
Q

If one parent is a carrier for an Autosomal dominant disorder, what is the likelihood a child will have it?

A

50%

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20
Q

What are the types of autosomal dominant disorders?

A

Reduced/Incomplete Pentrance
Variable Expressivity
De novo mutation

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21
Q

Reduced/Incomplete Penetrance

A

If a person has a mutant gene, but doesn’t or only partially expresses it phenotypically

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22
Q

Variable Expressivity

A

Expression can be identified in all effected persons, but to different extents

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23
Q

De novo mutations

A

AD disorder where neither parent is affected and there is no family history in the pt

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24
Q

Autosomal Recessive Disorder

A

Trait is expresssed only if both genes at a given loci are mutated
Parents of the affected pt usually don’t show the disease phenotypically
Many are enzyme defects leading to metabolic dysfunciton
Age of onset is early
Complete penetrance is common

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25
Q

If both parents are carriers of an AR disorder, what is the liklihood that the kids have the disorder?

A

25% of having the disorder

50% of being carriers

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26
Q

What are heterozygous carriers of AR disorders unaffected?

A

They typically have reduced, but still adequate levels of normal functional enzymes

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27
Q

X-linked disorders

A

aka Sex-linked

All the mutations are on the X-chromosome

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28
Q

What type of disorder is the most common X-linked disorder?

A

X-Linked Recessive

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29
Q

X-Linked Recessive

A

Females having 2 X-chromosomes are usually unaffected
Heterozygous females are carriers
Homozygous females express the disease
Hemizygous males express the disease

30
Q

Lyonization

A

Rarely, heterozygous females may demostrate full expression of X-linked recessive diseases
16 days post-conception, most of (>75%) of one X-chromosomes are inactivated randomly
Results in the formation of a Barr body in each cell
Either the maternal or paternal X may be inactivated

31
Q

What are some diseases caused by Mutations in structural proteins?

A

Marfan Syndrome

Ehlers-Danlos Syndrome

32
Q

Marfan Syndrome cause

A

Autosomal Dominant
Mutation of the FBN1 gene
The mutation results in abnormal fibrilin; which is important for normal elastic fiber production

33
Q

Marfan Syndrome Symptoms

A 
Tall, thin body appearance
-abnormally long legs
-Arachnodactyly
Dislocation of the eye lens
Aortic aneurysm leading to heart failure and aortic rupture
34
Q

Ehler-Danlos Syndrome

A

Mutation causes a problem with collagen synthesis

35
Q

Ehler-Danlos Syndrom Symptoms

A

Hyperextensible skin and hypermobile joints
Skin fragility and delayed wound healing
Rupture of colon and large arteries
Hernia

36
Q

What is the signature disease caused by mutations in genes encoding receptor proteins or channels

A

Familial Hypercholesterolemia

37
Q

Familial Hypercholesterolemia cause

A

Autosomal Dominant
Mutation in the gene that encodes the LDL receptor - resulting in impaired metabolism and increased LDL cholesterol in the plasma

38
Q

Familial Hypercholesterolemia Symptoms

A

Multiple Xanthomas (lipid filled lesions) of the skin and premature atherosclerosis

39
Q

Heterozygous Hypercholesterolemia

A

2-3x more LDL than healthy individuals

40
Q

Homozygous Hypercholesterolemia

A

> 5x more LDL than healthy individuals

Often die via MI by age 20 - early treatment can help, but pts are still high risk

41
Q

Iomitapide

A

Recently approved drug to help treat Homozygous Hypercholesterolemia

42
Q

What are some diseases caused by Mutations in Enzyme Proteins?

A

Phenylketonuria

Lysozomal Storage Diseases

43
Q

Phenylketonuria

A

Autosomal Recessive

Severe lack of phenylalanine hydroxylase leading to hyperphenulalaninemia and PKU

44
Q

Phenylketonuria symptoms

A

Affects 1:10k caucasian infants
Affected infants seem normal at birth, bu elevated phenylalanine levels impair brain development and cause mental retardation by 6 mo

45
Q

Phenylketonyuria treatment

A

Screening of newborns is mandatory in the US

Restricted dietary sources of phenylalanine will prevent the development of retardation

46
Q

Lysozomal Storage disease

A

Autosomal recessive
Commonly affects infants and youn children
Accumulation of insoluble large molecules in macrophages, leading to hepatosplenomegaly
-this decreases the cell’s efficiency and makes it useless
Frequent CNS involvement leads to neuronal damage, mental retardation, and/or early death

47
Q

Mucopolysarccharidoses

A

Autosomal Recessive
Caused by lack of any one of several enzymes necessary to degrade mucopolysaccharides
Affected patients have coarse facial features, clouding of cornea, stiff joints, and mental retardation

48
Q

Hurler Disease

A

Autosomal Recessive
Caused by deficiency of alpha-L-iduronidase
Life expectancy is 6-10 yrs
Bone marrow transplant or enzyme replacement may improve outlook, but not all aspects are corrected

49
Q

Hunter Syndrome

A

X-Linked
Deficiency in L-iduronate sulfatase
Absence of corneal clouding and milder clinical course, but very similar to Hurler’s

50
Q

What are some examples of things with Multifactorial Inheritance

A 
Height
Weight
BP
Hair color
Diabetes
Hypertension
Gout
Schizophrenia
51
Q

What causes 50% of first trimester spontaneous abortions?

A

Chromosmal abnormalities

52
Q

What are the different Numeric abnormalities of chromosomes?

A

Polyploidy

Aneuploidy

53
Q

Euploidy

A

Normal chromosome count

46

54
Q

Polyploidy

A

An increased chromosome count that is a multiple of what is normall seen
ie 3x23 = 69
4x23 = 92

55
Q

What is Aneuploidy and what are the different types?

A

Any number that is not an exact multiple of the normal count
Trisomy
Monosomy

56
Q

Trisomy

A

Extra chromosome

57
Q

Monosomy

A

Missing a chromosome

58
Q

What are the different Structural Autosomal Abnormalities?

A

Translocation
Deletion
Inversion

59
Q

What causes Structural Autosomal Abnormalities?

A

Results from chromosome breakage followed by loss or rearrangement of material

60
Q

Translocation Autosome abnormality

A

Transfer of a part of one chromosome to another nonhomologous chromosome (a different chromosome)
-known as reciprocal translocation

61
Q

Deletion Autosomal abnormality

A

Loss of a portion of a chromosome

62
Q

Inversion Autosomal abnormality

A

Chromosome breaks in two, and the released fragment flips and is reunited

63
Q

Trisomy 21

A

Downs Syndrome
Due to meiotic non-disjunction of chromosome 21 during ovum formaiton
More likely in older mothers

64
Q

Trisomy 21 Symptoms

A 
Mental retardation
Epicanthic folds
Flat facial profile
Cardiac malformations
Increased susceptibility to infections
Large tongue
Increased risk of acute leukemia
65
Q

Jimmy Kleinfelter syndrome

A

Male hypogonadism where there are at least 2 X chromosomes and one or more Y chromosomes
Most common form is XXY
Pts are phenotypically male

66
Q

Kleinfelter syndrom Symptoms

A 
Increased length of lower limbs
Reduced body hair
Gynecomastia
Hypogonadism
Most common form of male sterility
Increased frequency of taurodontism
67
Q

Turner Syndrome

A

Partial or complete abscence of one of the X chromosomes (45 total chromosomes)

68
Q

Turner Syndrome Symptoms

A 
Short stature
Webbing of neck
Low posterior hairline
Shield-like chest
High-arched palate
Variety of congenital cardiovascular malformations
Failure to develop secondary sex characteristics
Amenorrhea (absence of menstruation)
69
Q

Prenatal indications for genetic analysis

A

Mother’s age >34 yrs
Parent is a carrier of a chromosomal translocation or X-linked disorder
Hx of previous child with chromosome abnormality

70
Q

Postnatal indications for genetic analysis

A 
Mutiple congenital abnormalities
Unexplained reatardation 
Suspected aneuploidy
Suspected sec chromosomal abnormality
Infertility
Multiple spontaneous abortions

SP 16 - Path Test 2 (5 decks)

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