What are the two factors responsible for variation in organisms?
genes and environment
Define Mendelian trait and what is the "pattern of inheritance"?
- trait due to single gene
- either/or pattern
- ex. pea plants, huntington's disease
Define Multifactorial traits
- traits influenced by the environment
- ex. heart disease, intelligence, skin color, height, weight..
Define Polygenic traits
- due to activity of >1 gene
- bell curve distribustion of phenotypes
True or False..
It is difficult to predict recurrence for polygenic traits?
Define Empiric Risk and what it's based on
- predictions of recurrence based on trait's incidence in specific population
- based on observations/epidemiological studies
- % of phenotypic variation due to genes
- H=1 genes only
- H=0 environment only
- Heritability is a component of phenotype attributed to genes
Define Correlation coefficient
proportion of genes relatives share
-Mendelian trait: expect it in 50 sibling pairs
-Trait is only observed in 37 pairs
What is the heritability?
State the degree and percent of shared genes for each:
2. Parent and child
3. Uncle/aunt and niece/nephew
4. Grandparent and grandchild
5. First cousin
- 1. degree 1, 50%
- 2. degree 1, 50%
- 3. degree 2, 25%
- 4. degree 2, 25%
- 5. degree 3, 12.5%
- adopted people share environement, but not genes
- share genes but not environment with biological parents
- better info than adoption studies
- Concordance- percent (%) of pairs in which both twins express the trait
- stands for: single nucleotide polymorphism
- a nucletoide site with more than one allele is a polymorphism
- site is polymorphic is allele is present in >1% of the population
- on average, between two random individuals, there is one SNP every 1000 bases
- --> ~3 million differences
- studies which compare group of interest
- controls are matched: age, ethnicity, gender, enviornment
- if SNP is present more often in cases then controls, it is associated with trait and implies SNP may be near gene impacting trait