Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
17 Cards in this Set
- Front
- Back
|
What is meant by "narrow sense heritability"? |
This is using knowledge of pedigree (relatedness) and phenotypic data to calculate the heritability of a phenotype. It uses expected, not actual IBD |
|
|
Define IBD |
Identical by Descent - the proportion of matching alleles on each chromosome |
|
|
What is heritability? |
The proportion of the variation of a phenotype that can be attributed to genetics. |
|
|
Describe segregation analysis |
Modes of inheritance: Dominant, Recessive, Additive. Presence of a mutated SNP i.e. Genotype AA=0, AG=1, GA=1, GG=2. Regress phenotype on genotype. Segregation analysis describes these |
|
|
If a is the additive effect of a model with genotype, and d is the degree to which the mutation is dominant, what kind of relationship is described where d=-0.25 and a=0.3? |
This is recessive. Homozygous wildtype would show effect: mean-a(0.3) Heterozygous would show effect mean - d(0.25) Homozygous mutant would show effect mean+a(0.3) So having 2 copies of the mutant strain makes a big difference
|
|
|
If a is the additive effect of a model with genotype, and d is the degree to which the mutation is dominant, what kind of relationship is described where d=0.25 and a=0.3? |
This is a dominant mode of inheritance. Homozygous wildtype would show effect: mean-a(0.3) Heterozygous would show effect mean + d(0.25) Homozygous mutant would show effect mean+a(0.3) The second copy does not add much to the effect |
|
|
If a is the additive effect of a model with genotype, and d is the degree to which the mutation is dominant, what kind of relationship is described where d=0 and a=0.3? |
This is additive. Homozygous wildtype would show effect: mean-a(0.3) Heterozygous would show effect mean Homozygous mutant would show effect mean+a(0.3) The each copy have the same effect |
|
|
Kinship |
The average of k1/4+ k2/2 where k1 is the proportion of SNPs matching on 1 chromosome and k2 is the number matching on 2 chromosomes. i.e. MZ twin k1=0 k2=1 so kinship=.5 full sibs k1=0.5, k2=0.25 so kinship= .25 parent-child k1=1, k2=0 so kinship =0.25 |
|
|
Relatedness |
2(Kinship) |
|
|
What is the relatedness of a Grandparent to a Grandchild? |
One way of working this out is that the Grandparent is a parent of a parent, so 0.5 of 0.5 related =0.25. Another way is that there are four grandparents contributing to the potential genome of the grandchild so the prob it is from the grandparent is 1 in 4. |
|
|
What is the relatedness between a Niece and an Auntie |
Auntie is a full sib of a parent, so 0.5 of 0.5 =0.25. K1 is 0.5 - because K1 between sibs is 0.5 and K1 between parent child is 1. |
|
|
In terms of relatedness - how do you determine degree and common ancestor |
degree - number of links in the tree. i.e full sibs degree=2 S1 - Parents - S2, parent child degree=1 parent- child cousins degree= 4 C1- Parent- Grandparents - Parent-C2 Common ancestor (T) - number of common ancestors (at the point referenced in "degree")? full sibs T=2 (both parents) parent child T=1 parent- child cousins degree= 2 (the two grandparents) |
|
|
Where T is number of common ancestors, and S is degree, what is kinship? |
kinship= T* 0.5^s+1 |
|
|
What does SNP stand for? |
Single Nucleotide Polymorphism. A mutation which affects a single base pair |
|
|
What role does environment play when considering heritability |
Environment is a noise variable. The risk of skin cancer in two siblings could be partly explained by genetics but also by sun exposure. Often people with similar genes also share similar environments. Narrow sense heritability does not deal with interactions between genetics and environment. |
|
|
What is the mixed model for heritability? |
The mixed model differs from narrow sense heritability studies using estimated relatedness as it calculates actual relatedness between two individuals. |
|
|
what are the drawbacks of twin studies? |
Assumes additivity Relies on the accuracy of the assumptions Environment may vary between DZ and mz twins Ignores cross terms (interactions?) |
