human genetics test final Flashcards
how do you figure out an incest child having the disease?
pathway tracingg
what is pathway tracing?
following the allele away from the known location and moving away from the reference point and toward the point in question
what is a primary relative?
immediate relative (just one position away along a descent line)
what is a secondary relative?
slightly removed ( two positions away)
what is a tertiary relative?
more distant relative (3 positions away)
are there fourth degree relatives?
yes, but we donメt go out that far
def of multifactorial inheritance
genetics is due to many factors, some genetic some not
two fundamental forms of multifactorial inheritance?
multiple genes determine trait (polygenic inheritance), and a single gene and enviromental factors
what are the early cases of multifactorial inheritance?
penetrance, variable expressivity
what is the example of polygenic inheritance used?
wheat grain color
what do you begin to see if one begins to put the phenotypes on a graph?
normal distribution (bell curve)
what color of wheat is most common?
pink (amber as he says it)
what else seems to work in the same way as wheat color?
human skin color
what determines the higher continuous variation?
the greater the number of genes involved in the polygenic system
what happens if you add in chances for additional enviromental variables to a polygenic system?
the variation becomes very smooth and continuous, and therefore it becomes very difficult to dissect out the genetic component
what is the genetics of obesity?
complex multifactorial trait
what are the factors of obesity?
a trait where you wont get saitity, and the enviromental is where you over eat and not exercise
what is the genetics of intelligence?
complex multifactorial trait
what did the Bach pedigree look like?
it LOOKED like musical genius was a autosominal dominant trait
is the use of a pedigree a good way to be used as convincing evidence for a complex mulifactorial trait?
it may be problematic
what should you use instead?
comparing specific genotypes placed in differing or same enviroments
what is an example of genotypes living in different enviroments?
monozygous twins that have lived in different enviroments
what are the results of the monozygous twin studies?
the twins yeild substantial evidence for a GENETIC basis to intelligence
what university has an ongoing monozygous twin study?
university of minnesota
what is the final conclusion of the twin studies?
merely confirm that both genetic and enviromental factors are important, although many would argue that its evidence for genetic factors
what is another way to approach mulitfactorial inheritence? (other than pedigree or genetic cohort)
heritability
def of heritability
an estimate of the population phenotypic VARIATION that is due to genotype
another def of heritabilityナ.
the fraction of the phenotypic variability in the population which is determined entirely by genotype
heritability = 1
the population phenotypic variance is likely due entirely to genotype
heritability = 0
the population phenotypic variance is likely due entirely to enviroment
what does heritability a measure of?
correlation between genotype and phenotype
what does inheritance tell us?
the HOW of a trait
what does heritability tell us?
how MUCH (genetic predisposition)
how is heritability looked at in the final analysis?
abstraction of limited value for routine inheritance prediction or understanding specific genetic factors
what is the newest way to approach multifactorial inheritance?
find the correlation b/t some specific DNA marker sequence found in 2 populations, one with trait one w/o
what have single nucleotide polymorphisms done?
proven to be helpful to identify genes for a susceptibility to the development of a disease
what are empirical risk figures?
a gathering of observational studies that might be used to predict the future based on the past
what do empirical risk figures give you?
only provide data based on similar prior situations, not anything b/t genetic or enviromental
what are the common ways to approach multifactorial inheritance?
pedigrees, twin studies, heritability, DNA associated studies, empirical risk tables
pro/ con pedigree
attemping to model the disease- but not good except for finding broad patterns
pro/con twin studies
difficult to use in practical way
pro/con heritability
complex mathematical derivation and of limited practical use
pro/con DNA associated studies
requiring difficult laboratory testing and only susceptibilities
pro/con empirical risk table
requires large statistical databases and do not explain mechanisms
familial risk compared to gen pub?
considerably higher
familial risk over generations?
drops sharply with increasing distance to index case
what is the risk of a first degree relative?
roughly a square root of the population risk
what is higher when more than one family member is affected?
recurrent risk
what are the two basic ways to look at human multifactorial traits?
1)model the disease 2)develop empirical risk figures
how do you model the human multifactorial trait?
look for a basic pattern of inheritance using a pedigree, then develop rules, as needed, for deviation from simple predictions
how do you use the empirical risk figures to look at a human multifactorial trait?
rely on PRIOR OBSERVATIONS to est statistical tools of prediction
def of adolescent idiopathic scoliosis (AIS)
multifactorial condition of spinal curvature laterally >10 degrees
how common is AIS
1 in 30 in persons 10-16 years of age
how does the pedigree of AIS look?
autosomal dominant with reduced penetrance
what is the penetrance of AIS?
~60%
how do you find the penetrance of AIS?
from one parent, a simple autosomal dominant model would have to have generated a recurrent risk of 50% and yet the statistic is 29% so 0.5x0.6=0.3 so 60% penetrance
def of spondylolysis/ spondylolisthesis
multifactorial conditions of spinal pars interacticularis and a common source of low back pain
spondylolysis=
a stress fracture of the pars of the vertebral body
spondylolithesis=
a slippage of vertebral bodies which may happen due to spondylolsis or degenerative changes with age
how common are spondylolysis?
~5% of pop
how common are spondylolithesis?
~2.5%
what is the general pedigree look of spondys?
autosomal dominant with reduced penetrance
what is the penetrance of spondys?
~40%
def of congental dislocation of the hip?
(acetabular dysplasia) multifactorial anomaly characterized by displacement of the femoral head outside of acetabulum prior to birth
how common is hip dislocation?
1 in 1000 births
what model does hip dislocation follow?
autosomal dominant with reduced penetrance
what is the recurrence risk for sibs in congenital dislocation of the hip?
about 5%
what is ankylosing spondylitis?
multifactorial autoimmune “spondyloarthropathy” condition. Chronic painful progressive inflammatory arthritis primarily affecting spine and si jts
what antigen is ankylosing spondylitis correlated to?
HLA- B27
how common is AS
1 in 400
neural tube defects (including spina bifida)
multifactorial condition characterized as an embryonic failure to fully close the developing neural tube
what chomosomes are neural tube defects linked to?
17q11 and 6q27
how common are neural tube defects?
1 in 1000
what is the recurrence risk for sibs in neural tube defects?
~4%