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1
Q

What is Disease?

A

A disease is the result of a certain pathogenetic process that disrupts the well-being of an organism.

2
Q

What is the process of disease?

A

infection and noninfectious

3
Q

What is an example of a noninfectious disease?

A

aging

4
Q

What is chronic disease?

A

A disease or health condition that lasts longer than three months, sometimes for the remainder of one’s life.

5
Q

What is acute disease?

A

A disease or health condition that occurs and subsides within three months, usually within days or weeks.

6
Q

What are examples of acute infection disease?

A

The cold virus infection (usually adenovirus) —causes inflammation in the mucous membranes lining the nose and throat.
Influenza—a viral infection of the respiratory tract.
Mononucleosis— Known as “the kissing disease,” common in teens; it’s a virus that multiplies in the lymphocytes.

7
Q

What causes mono?

A

Epstein-Barr virus

8
Q

What are the symptoms of mono?

A

Fever, fatigue, sore throat, atypical lymphocytes

9
Q

What are rate of mono in children, teenagers, and adults?

A

childresn - 50%
teenagers - 35-50%
adults - 90-95%

10
Q

mono in children

A

In children, infection with EBV usually cause no symptoms or disease is indistinguishable from the other mild, brief illnesses of childhood.

11
Q

What is the EBV latency of mono?

A

EBV infects B-cells of the immune system and epithelial cells. Once the virus’s initial lytic infection (acute phase) subsides, EBV latently persists in the individual’s B cells for the rest of the individual’s life.

12
Q

What are the EBV cells capable of?

A

Able to reactivate a virus and to shed viral particles

13
Q

What is latent infection?

A

an extreme version of a persistent infection

Slow and abortive infectionsare more complicated variants of a persistent infection

14
Q

What is EBNA-1 and 2?.

A

EBNA-1 is involved in promoting viral DNA replication

EBNA-2 is a transcription factor with viral and host cell targets

15
Q

What is LMP1 and 2?

A

LMP1 expression in rodent cell lines results in transformation
LMP2 associates with src and several other tyrosine kinases

16
Q

When is EBV under control of the host immune system?

A

in the chronic latent infection

17
Q

When does immune supression occur?

A

autoimmune diseases, organ transplant

18
Q

What causes post-transplant lymphoproliferative disorders?

A

reactivation of latent EBV
A child or a rare adult who was never infected before onset immuno-suppression lacks prior immunity, placing the patient at high risk for active viral infection and progression to neoplasia

19
Q

Where is KSHV found?

A

Sarcoma kaposhi – found in patients who has HIV

20
Q

Burkitt lymphoma

A

EBV if found in ALL cases of endemic Burkitt lymphoma, but many EBV infected people remain lymphoma free

21
Q

What is the advantage of anti-apportial viral genes of EBV?

A

EBV’s anti-apoptotic viral genes provide a survival advantage to the lymphocyte that carries EBV
It expresses a number of alien genes (from EVB) and some host genes are expressed stronger than they should

22
Q

What is the role of LMP1 in EBV?

A

-LMP1 expression in transgenic mice leads to B cell lymphoma; expression in fibroblasts leads to tumors in nude mice
-LMP1 accelerates B Cell Proliferation
-Upregulates adhesion molecules, CD23, CD40, IL-6, IL-10, etc.
-Activates NF-kB
LMP1 Inhibits apoptosis
-Upregulates Bcl-2, A20, Mcl-1

23
Q

What is LMP1?

A

the EBV-Carried oncogene

24
Q

What does LMP1 signaling stimulate?

A

Akt, NFκB, and Stat3 pathways

25
Q

How can normals cells infected with viruses be transformed into cancerous cells?

A

from expression or activation or viral oncogenes

26
Q

What can result from transformation?

A

transformation can result in integration of viral genes or genomes into the host genome

27
Q

What are the classification of human disease?

A

chromosomal
single-gene
polygenic = complex = multifactorial

28
Q

how do you find whether certain disease has a genetic component?

A
  1. Classic Family Study
  2. Twin studies
  3. Adoption studies
29
Q

What are the 3 criterias of classical family study?

A

1) Identify the family
- ascertain all affected individuals
- sometimes difficult due to non-disclosure (especially in psychiatry)
2) Determine the proportion of the relatives affected (according to the degree of kinship to the index case)
3) Calculate the lifetime risk for morbidity for various relatives

30
Q

What are the proportion of genes shared on the 3 degrees of relationship?

A

first - 50%
second - 25%
third - 12.5%

31
Q

What are examples of first degree relationship?

A

parents and children

siblings and sibling

32
Q

What are examples of second degree relationship?

A

grandparent and grandchild
uncle and nephew
half-siblings

33
Q

What are examples of third degree relationship?

A

great grandparents and great grandchildren
first cousins
half uncles

34
Q

how do you calculate the lifetime expectation morbid risk?

A

a = risk of siblings/population prevalence

35
Q

What is the difference between mendelian and complex disease

A

Mendelian Diseases: Exhibit Mendelian mode of inheritance

Complex Diseases: Not Mendelian but Appear to Cluster in families

36
Q

Why does family, twin, and adoption studies show greater risk to relatives of affected than population incidence?

A

that is simply because you share more genes with your relatives than with random stranger from the same population

37
Q

What is the difference between identical (MZ) and dizyogtic (DZ) twin studies?

A

identical twins (MZ) who share 100% of their genes, dizygotic (DZ) or fraternal twins, who share only 50% of their genes.

38
Q

What is the difference between concordance and discordance?

A

condorant - both twins carry the disease

discordant - only 1 twin carriers the disease

39
Q

What is the rate of concordance in genetic and environmental conditions?

A

genetic - 100%

environmental - 0%

40
Q

What are the difficulties with twin studies?

A
  1. Rarity of twins in the general population: (1 in 80 pregnancies)
  2. Concordant pairs are more likely to be enrolled in the study than discordant
  3. MZ twins often share more environment than DZ twins (closer to each other)
41
Q

polygenic inheritance

A

Each of the polygenes exerts a small (but additive) effect

on the continuous phenotype

42
Q

Oligogenic inheritance

A

Middle ground between monogenic and polygenic inheritance
Assumes that condition is defined by relatively small (finite, accountable) number of loci
Allows for some loci be more influential than others (like in epistasis)

43
Q

What is heritability?

A

Heritability is the proportion of phenotypic variation in a population that is attributable to genetic variation among individuals
It’s a genetic component – as opposed to environmental component –> 60%

44
Q

What is the mode of inheritance?

A

The mode of inheritance (autosomal dominant, polygenic, etc.) is a fixed property of a trait

45
Q

What is total phenotypic variance?

A

the sum of the variance due to genetic factors and to environmental factors

46
Q

Douglas Scott Falconer - Liability Threshold Model

A

Liability to the condition is polygenic and normally distributed.
People whose liability is above a certain threshold value are affected.

47
Q

What is an example of a dichotomous disease?

A

cleft palate. greater risk for relative than a cleft lip

48
Q

Liability threshold - cleft palate example

A

Siblings of affected individuals (curve shifted to the right) have a higher average liability than the population mean and a greater proportion of them have liability exceeding the threshold. Therefore the condition tends to run in families.

49
Q

what are the genotypes of Rare disease

A

GG (all sick)
AG (mostly sick)
AA (healthy)

50
Q

What is the probability of rare disease?

A

Disease prevalence ~1 in 1000
Individuals with GG are ~1000 times more likely to get disease
Frequency of G allele in controls ~ 5%
Frequency of G allele in cases ~ 96%

51
Q

What are the 3 ways to find common disease-common variant (CDCV) genes?

A
  1. linkage analysis
  2. association studies
  3. linkage disequilibrium analysis
52
Q

What is linkage analysis?

A

LINKAGE analysis quantifies the correlation between the trait and the marker at family level

53
Q

What is association studies?

A

ASSOCIATION study quantifies the correlation between the trait and the marker at population level

54
Q

What is the old-fashion study for linkage analysis of multifactorial disease?

A

At least 200 affected sib pairs (affected sib – not affected sib) + their parents
Analyzed with at least 300 polymorphic markers evenly spaced on chromosome

55
Q

What is the logarithm of odds (LOD)?

A

a statistical estimate of whether two genes, or a marker gene and a disease gene, are likely to be located near each other on a chromosome and are therefore likely to be co-inherited.

56
Q

How do you calculate LOD?

A

Probability of obtaining the results assuming the 2 loci are linked/ probability of obtaining the results assume the 2 loci are not linked

57
Q

What is Cloning Marfan Syndrome gene: fibrillin?

A

fibrillin is a connective tissue protein that makes up part of microfibrils, which are elastic fibers

58
Q

What does association studies test?

A

Test whether single-locus alleles or genotype frequencies are different between 2 groups (usually diseased subjects and healthy controls).

59
Q

How can you you compare genes in association studies?

A

Genotypes can be compared “directly”, i.e. using the sequences of actual genomes.

60
Q

How do you calculate Measure of Association (odd ratio)?

A

odds = p/(1-p)
p is probability
ex: off of minor allele carrier/ odd for non-carriers = (813/3,601)/(794/3.667) = (8133,667)/(7943,061) = 1.23

61
Q

odd ratio of association.

A

If the probability of the disease is 50%, odds are 1/1

If the probability of the disease is 25%, odds are 1/3 for disease or 3 to 1 against disease

62
Q

what is ankylosing spondylitis?

A

an increased frequency of HLA-B27 is observed in AS, Reiter’s disease, acute anterior uveitis, radiological sacroiliitis, symptomatic backache, and gram-negative reactive arthritis –> different manifestations of the same syndrome, which could be called “B27 disease”

63
Q

What is the B27 Frequence in AS?

A

8.8% in US population

64
Q

What is the percentage of getting AS if you have HLA-B27 Gene?

A

only 1-5% of people who carry the HLA-B27 gene develop ankylosing spondylitis

65
Q

What is a symptom of AS?

A

Bone ossification, leading to loss of curvature in spine, and a ridgid hunch posture

66
Q

how do you conduct Genome wide association analysis (GWA)?

A
  1. Scan the entire genome with a dense collection of genetic markers
  2. Calculate association at each polymorphic marker position along the genome
  3. Identify regions which show a significant associations
  4. Study possible disease-contributing genes from the linked region in functional assays
  5. studies involve thousands of patients
67
Q

What is linkage disequilibrium?

A

Markers close together on chromosomes are often transmitted together, yielding a non-zero correlation between the alleles.

68
Q

What is the importance of linkage disequilibrium?

A

It is important for allelic association because it means we don’t need to assess exact causal variant, but we see trait-SNP association with a neighbouring variant.
That allow us to impute some SNPs saving on the number of alleles tested

69
Q

What is NOD2?

A

NOD2 gene is associated with inflammatory bowel disease (as founded by GWA)

70
Q

How is NOD2 activated?

A

NOD2 is activated by the bacterial peptidoglycan muramyl dipeptide (MDP).

71
Q

What happens when NOD2 gene is deficient?

A

When NOD2 gene is deficient, it attenuates antibacterial activity in the intestinal crypts and decreases expression of α-defensin 4

72
Q

What are examples of GWA?

A

Metabolic/cardiovascular disease: type 2 diabetes, obesity, heart disease, atrial fibrillation
cancer: breast, prostate, colorectal
inflammation-related diseases: asthma, rheumatoid arthritis, type 1 diabetes, gallstones, delicate diseases, restless leg syndrome

73
Q

what are examples of non-inclusive diseases?

A

parkinsons, schizophrenia, bipolar stroke, hypertension

74
Q

what is linkage?

A

A linkage is the cosegregation of a disease or trait with a specific genomic region in multiple families

75
Q

What is association?

A

property of alleles: a specific allele of a gene or marker is found as co-inherited with a disease or trait in a population

76
Q

What is linkage disequilibrium?

A

the presence of linkage AND association

Affected individuals inherited the mutation from a common ancestor (within IBD segment)

77
Q

What are linked alleles?

A

Closely linked alleles within IBD are also associated with disease (located within the same haplotype)

78
Q

What is LMP1?

A

EBV oncogene

79
Q

What are some oncogenic DNA Viruses?

A
andenoviridae
herpesviridae
poxviridae
papovaviridae
hepadnaviridae
80
Q

What are some oncogenic RNA Viruses?

A

retroviridae

HTLV-1 and 2

81
Q

What is the difference between fraternal and identical twins?

A

fraternal - products of 2 different sperms and egg conceived at the same time
identical - 1 sperm and eggs that are split apart to form separate embryos

82
Q

What was the conclusion of AJ Stunkard adoption study on human obesity?

A

genetic influences have an important role in determining human fatness in adults, whereas the family environment alone has no apparent effect.

83
Q

difference in the incidence of the disease between genders.

A

If disorder is more common in BOYS, the relatives of affected GIRLS will be under the greater risk.

84
Q

what is high penetrance genetic variant?

A

Mendelian single gene diseases, 100% penetrant

EX: Huntington’s Disease and Autosomal dominant

85
Q

What causes HUNTINGTON?

A

excess CAG repeats in huntington’s protein gene

86
Q

what is reduced penetrance genetic variant?

A

some genes lead to a predisposition to a disease, 80% penetrant
EX: BRCA1 & BRCA2 genes can lead to a familial breast or ovarian cancer

87
Q

What is complex diseases?

A

diseases requiring alleles in multiple genes, (and) having multiple causes or pathways

88
Q

What are examples of complex diseases?

A
  1. Many cancers (solid tumors) require somatic mutations that induce cell proliferation, mutations that inhibit apoptosis, mutations that induce angiogenesis, and mutations that cause metastasis
    Cancers are also influenced by environment (smoking, carcinogens, exposure to UV)
  2. Atherosclerosis (obesity, genetic and nutritional cholesterol)
89
Q

How is positional linkage detected?

A

Positional linkage is detected computationally with GENEHUNTER or MAPMAKER/ SIBS software

90
Q

how are multifactorial diseases identified?

A

Identified areas are called “IBD” (identical by descent) or “shared segments”