Biol133


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 geneeither/or patternex. pea plants, huntington's disease


Define Multifactorial traits


traits influenced by the environmentex. heart disease, intelligence, skin color, height, weight..


Define Polygenic traits


due to activity of >1 genebell curve distribustion of phenotypes


True or False..
It is difficult to predict recurrence for polygenic traits?
True False


true


Define Empiric Risk and what it's based on


predictions of recurrence based on trait's incidence in specific populationbased on observations/epidemiological studies


Define Heritability


% of phenotypic variation due to genesH=1 genes onlyH=0 environment onlyHeritability is a component of phenotype attributed to genes


Define Correlation coefficient


proportion of genes relatives share


Heritability example:
-Mendelian trait: expect it in 50 sibling pairs
-Trait is only observed in 37 pairs

What is the heritability?


.37/.50= .74


State the degree and percent of shared genes for each:
1. Siblings
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%


Adoption Studies


adopted people share environement, but not genesshare genes but not environment with biological parents


Twin Studies


better info than adoption studiesConcordance- percent (%) of pairs in which both twins express the trait


Define SNP


stands for: single nucleotide polymorphisma nucletoide site with more than one allele is a polymorphismsite is polymorphic is allele is present in >1% of the populationon average, between two random individuals, there is one SNP every 1000 bases--> ~3 million differences


Association Studies


studies which compare group of interestcontrols are matched: age, ethnicity, gender, enviornmentif SNP is present more often in cases then controls, it is associated with trait and implies SNP may be near gene impacting trait