Single Gene Variation

Origin of Genetic Variation - Mutations as the origin of Genetic Variation

1. what is a mutation?
   • Error in replication/ meiosis leading to a change in a base
2. Mutations do not happen preferentially “when we needthem”, they happen randomly.
3. Many mutations are “bad”, but rarely(though it happens), a mutation is “good”.
4. Some mutations “do not matter”, like “GCT” and “GCC” are tanslated to Alanine.
5. Is itmore important that this mutation is passed on by meiosis or mitosis?
   • Meiosis, because it will get pass down to offspring

Shortcomings of the Single Gene Model - Sources of Genetic Variation: Why the simple single gene/2 allele model is insufficient

1. More than one gene controls trait
   • True for almost every phrnotype
2. Variable “penetrance”
   • Mutant froms may “sometimes” affect phenotype but now always do so.
   • BRCA1 breast cancer susceptility, buts BRCA1 breast cancer phenotype is not fullt penetrant- you CAN be “bb” and still have all non-cancerous cells in breast.
     • BB or Bb is 12% risk of breast cancer
     • bb is 60% risk
3. Interaction among genes: “epistasis”
   • Effect of genotype at one gene modifies effects of genotype at another gene.
   • Pea flower color: C gene’s protein, C protein, is upstream of the P gene’s protein - P protein. If there is pp the flower is white, on the other hand, Px is the pink flower.
4. THere can be >2 alleles at a locus!
   • ABO blood types
     • Blood genetypes: AA, AO, BO, AB, OO
     • Blood phenotypes: A, B, AB, and O
5. Environment, and interactions with it.
   • We will begin “heritability” soon.
   • Sun tanning.
     • In absence of sun, do not tan(Environmental effect).
     • Some people naturally taneasier than others(Interaction of environment with genetics)

Mutations and Complex Traits

Mutations Rates - Mutation “Rates”: How often do mutations happen?

1. Mutations “rate” per generation
   • Depends on type of mutation
   • Specific base to specific base (A->G)
   • Specific base to “any different” base (A-> nonA)
   • Other types(inversions, translocations, deletions)
   • Anythins in a gene that tields a phenotype
   • There is the show, if the worm mutation rate to human, how many base mutations do human have? and the ans is 65 new mutations - - Mutations introduce a lot of variation into populations

Mapping Complex Traits - Principles of mapping complex traits

• Most variable traits people study are conteolled by many genes
  • Fruit size
  • Human height
  • Bristle numbers in Drosophila
  • Many diseases
    • Cancers
    • Diabetes
    • Schizophrenia
• QTLs
• 
• Association of marker genotype with phenotype
  • Markers near (“linked to”) gene(s) causing different phenotypes will show an association with that phenotype
  • If there are many genes, and/ or if the effect is “complicated”, the assocation may not be very strong.

Complex Traits in Crosses

1. 
2. Association depicted using “LOD” plot
3. You try it ! and ans is between B and CPPT

Association Studies

Genome-wide Association Studies - Mapping Complex Traits in Populations: Genome-wide association studies (GWAS)

Supplemental Materials, Genetics III

Clikck here

与其借助第三方服务天天担心挂，还不如将自己的服务器资源利用起来。Isso就是自建评论系统的一种方式。（官网需要fq.）

Install Isso

测试自Ubuntu服务器。本来官网文档里没那么多戏，但是我一直报错。。又安了很多其它包。

$ sudo apt-get install python3-dev
$ sudo pip install isso
$ sudo apt-get install sqlite3

# 可能需要：
$ sudo pip install werkzeug
$ sudo apt-get install libffi-dev
$ sudo pip install misaka