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89 Cards in this Set

  • Front
  • Back
what is dichotomous characteristic?
Either you have or do not have the disease
What is continous chracteristic?
characteristics everyone has but to different degree such as height, bp, weight
Multifactoria diseases are
combination of genetic and environmnetal causes which applies to most common diseases
Define fully penetrant:
Other genes and enrionmental factors have no effect---mendelian
Define low penetrance
plays a small part, along with other genetic and environmental factors
Unique charcteristic of MS
genetic factors play a major part in determining susceptibility but each individual factor has a low penetrance
Wat is the chronic lifetime risk of a multifactorial disorder in western population?
Polygenic is what?
Caused by the presence of disease allele at mutliple genetic loci
Polygenic inheritane is also known as what?
quantitative inheritance
What is polygenic inheritance determined by?
It is determined by many genes each having a small, additive effect
ex: bp, height,
What is regression to the mean?
A simple genetic model in which the distribution of a certain chracter is the same in each generation
Is regression to the mean also seen for non genetic factors?
YES but does not prove that it is 100% genetic
What is the sume of the variance of a phenotype?
The sum of the genetically dtermined variation and environmentally determined variation
What is heritability
The proportion of the total phenotypic variance of a condition which cuased by additive genetic inheritance
What is the value given to H when it is genetically determined?
What is the value given to H when it is environmental factors?
What is the range given to multifactorial diseases?
What is the liability/threshold model
It isused to solve the apparent contradiction between a continuous distribution of a trai and the discontinous distribution of mutlifactoral disease
What does that threshodld postulate?
It postulates that susceptibility to the disease in a continous character
What are three different studies done to determine that genes have a significant influence on a disease?
familal aggregation, twin studies, and adoption studies
What does the familal aggregration test for?
It tets whether the disease prevalence in genetically related family members of affected individuals is increased over the prevalence of the disease in the general population
What is degree of relationship?
first degree?
Second degree?
third Degree?
What is used to test for familial aggregation/?
What does it quantify?
Familial relative risk
should be less than 1.
It quantifies the degree of risk to relatives
lambd r?
is the risk to relative R of an affect proband compared with population risk
What does teh twin study do?
compared the disease concordance rates among MZ twin pairs with those of DZ twin pairs
How much gens are shared between
MZ: 100%
What is the bias in twin studies?
they are dressed and treated the same in the same environment
What is the ideal experiment for a twin study?
To seperate MZ at birth
What is signifacnt of the adoption study?
It is used to determine if indiiduals are more concordant with their adoptive parents or with their biologic parents for a disease
What is the value given to H when it is genetically determined?
What is the value given to H when it is environmental factors?
What are some characteristics of monogenic disorders?
large familes
one disease gene/family
highlt penetrance genes
unaffected individuals also of use
What are some characteristics of multifactorial diseases?
small families
mutliple diseases genes/px
low penetrance genes
unaffected individuals can also carry
susceptibility disease
What mapping do you use for monogenc disorder?
parametric genetic mapping methods with lod score analysis
What mapping do you use for multifactorial?
Non-parametric genetic mapping methods with affected sibpair analysis
-uses large cohorts of cases and controls
What is identical by descent?
The same identical allele inherited from the same parent
What is identical by state?
The same allele but not identical..
What are the problems associated with identical by state?
becomes a problem when px are unavailable for genotyping
When does IDS occur?
1. when one of the parents is homozygous for a maker allele
2. when parents are heterozygoous for the sdame maker allele
What do you do to conduct a sib pair study?
1.Collect families with at least 2 affected siblings
2. perform a genome wide scan with regular spaced polymorphinc makers
What is significant of hot spot mutation?
Seen on many different haplotypes so px are usually unrelated
ex. 1138T>A in FGFR3 in achrondrodysplasia
What is significance of founder mutations?
If share a haplotype than share an ancestor.

ex. Cys282Tyr in HLA like gene on HSA6p21 in Haemochromastosis
What is linkage disequilibrium?
Shows that the percentange of haplotype should be a certain percentage but happens at a different percentage

ex C282Y Mutation cuasing hemochromastosis and HLA -a3
should be 3.3% but found at 15.6%
What are haplotypes?
Copy if the ancestral chromosomal region in which the mutation occurred.

identification of surrounding region indirectly detects the mutation
What does the case control design test for?
Test for differences in genetic marker frequency beetween affected cases and unaffected controls
What is the percentage of DNa variation in affected cases?Unaffected controls?
55% , 20%
What is the odds ratio?
What are the advantages of a case-control study? disadvantages?
easy to collect cases and controls
detection of risk alleles with small
lamda values
matched control group needed
sample size is important
Genes with small relativevrisks require large numbers
small nucleotide polymorphism
What is the mutation rate of SNP?
10^-7 to 10^-8 per generation
mutationally stable
What are some characterisitics of linkage studies?
known pedigree/relationship btw px
no of recombination evens btw px is low
large regions of DNa shared
limited number of genetic makers required
What are some chracteristics of association studies?
unknown population
no of recombination events between unrelated px is high
small regions of DNA shargin btw unrelated px
larger no. of genetic markers required
Strength of association depends on age and number of mutation
What is the transmission disequilibrium test?
analyses affected individuals plus parents
a= number of times a heterozygous parent trasmits allele 1 to an affected child
b= number of times the ther allele is transmitted
What is celiac disease?
most common food tolerance in western population
abnormal immune response to gluten proteins
What is concordance study on MZ and DZ on celiac disease?
MZ: 86%
DZ: 20%
What are the results of CD on general population and in siblings of CD px?
gen pop: .5%
in sibling: 10%
95% of CD px express this allele:
HLA-DQ2 or HLA-DQ8 heterodimer
25% of CD px express this allele:
What is the percentage of the general population expressing CD?
What chromsome linkages are there with CD?
6 (lod aorund 7) and 19 (lod around 3)
What haplotype is associated with Chromsome 19
What does the MYO9b do?
encodes an inconventiional myosin molecule that has a role in actin remodeling of epithelial enterocytes
- immunogenic gluten peptide can enter the deeper mucosal layer- initiating the inflammatory response
What is Hirschsprung disease?
Absense of nerve cells in the large bowel, no bowel movement causing abdominal distension
What is the recurrence risk?
What is the sex ratio for hirschspring disease?
What is the gene and ligand involved in system 1 of the hirschspring disease?
RET-promotes neural crest stem cell migration to the intestine

What is the penetrance percentage for RET in famililal caes and sporadic cases?
50-70%; 15-35%
What role does GDNF and NRTN have?
GDNF has a role in migration of neural crest cells and NRTN promotes their survival
What genes are involved in system 2 of HD?
EDNRB: recessive, invovled not only ins pread of neual precursors from the small bowel to the large bowel, but also of melanocytes
What is diabetes mellitus?
autoimmune disorder wish destroys pancreatic islet beta cells
what MHC complex accounts for 40% of the familial aggregration?
MHC 6p21.3
HLA-DQ2/DQ8 is present in how many type 1 px?
What is absent in type px?
What is the population risk and siblings risk for type 1 diabetes?
What is the reccurence risk for an offspring from an affected female?affected male?
How many people have type 2 diabetes mellitus:
8% with a first degree relatives increases to 10-15%
What inheritance is maturity onset diabetes of the young (MODY)
What are the three type of gene affiliated with MODY?
MODY 2: glucokinase def.
50% of heterozygous women develop gestational diabeted
MODY 1 and 3: hepatocyte nuclear factor 1A and 4A respectively
What does HNF 1A and HNF 4a do?
HNF 1 A activator of HNF 4a: activation of liver specific genes in glucose, cholesterol and FA metabolism
What does peroxisome proliferator-activated receptor gamma do?
ligand dependent TF regulating gene involved in lipid and glucose metabolism and adipocyte differentiation
What did they find in type 2 diabetes when performed a whole genome association
transcription factor 7 like 2
Zine transporter SLCC30A8
two coromosomal loci containing genes involved in beta cell development of function
What is strongest risk factor for AD?
5% over the age of 65
20% of the age of 80
What are the three genes associated with early onset AD
1. amylod precursor protein (<1%)
2. Presenilin 1 (50% of AD)
4. Presenilin 2 (<1%)
What is APP?
cell surface protein and is highly conversed in evolution
What are functions of P1 and P2?
involved with proteolytic cleavage of APP
What does abnormal cleavage of APP result in ?
Abeta42 which results in aggregation
What is the importance of ApoE4?
linkage analysis in late onset AD
increased association of E4 in AP px
apoE in AD amylod plauqes
What is the freq of apoE4 in ad px
40% w/ a risk of 30-50%
What are the effects of apoE4?
can inc lifetime risk from 9% to 29%
E4/E4: 15 fold increase
E4/E1,2,3: 3 fold increase