Lecture 31. Quantitative traits/heritability Flashcards
Why cant men transmit their x-chromosome to their son ?
They can only transmit their y chromosome
Where can association occur between ?
Between neighbouring markers and the trait, not just the causative mutation itself.
What does association decline with ?
- Time since the mutation occurred on the specific genetic background
- Map distance between markers and causative variation
- If influence of variant on trait is weak or swamped by other factors
- If the mutation in the gene which causes the trait is one of a number of mutations of similar effect
What is cystic fibrosis ?
A recessive disease that involves chronic bacterial infection, inflammation of lungs and high electrolyte level in sweat.
What are some symptoms of cystic fibrosis ?
- Salty tasting skin
- Persistent coughing
- Frequent lung infection
- Wheezing or shortness of breath
- Poor growth/weight gain in spite of a good appetite
Where is the cystic fibrosis gene located ?
Chromosome 7
What is the common cystic fibrosis mutation ?
Delta 308 mutation (deletion of codon for F by oligo hybridisation
What is another name for the gene involved in cystic fibrosis ?
Cystic fibrosis transmembrane conductance regulator (CFTR)
What is the function of cystic fibrosis conductance regulator (CFTR) ?
Regulates fluid flow within cells and affects the components of swear, digestive fluids and mucus
What is one of the thoughts behind the reason why the CFTR gene may have been naturally selected ?
Resistance to typhoid
What drug can help with cystic fibrosis ?
Ivacaftor (Kalydeco)
What cystic fibrosis mutation does Ivacaftor work for and how does it work ?
- G551D
- Improves transport of chloride through ion channel by binding to channels directly to induce a non-conventional mode of gating which increases the probability that the channel is open
What is sickle cell disease ?
- Individuals homozygous for beta-globin mutation produce abnormal hemoglobin
- Carriers produce mutant beta-globin that is co-dominantly expressed with the normal beta-globin and heterozygotes have mild anaemia
What does locus heterogeneity explain ?
How parents who are both affected with the same common recessive disorder produce multiple unaffected children
What so most mutations arise from ?
A result of endogenous errors in DNA replication and repair
When do mutations occur ?
During gametogenesis
What are de novo pathogenic mutations ?
Can occur at any time in post zygotic life - genetic mosiac
What are mendelian traits primarily associated with ?
Alterations to coding sequence of proteins
What is Duchenne’s disease caused by ?
Frame shift deletion
What is Becker’s muscular dystrophy disease caused by ?
In frame changes
What is Huntington’s disease ?
Late onset single gene disorder
What are complex genetic traits influenced by ?
- Alleles at two or more genes
2. Environmental effects
What is heritability ?
The estimate of what fraction of the total variation in a trait, observed within a given population, is due to genetic differences between individuals
What is relative risk ?
What is the risk of developing the disease/trait compared to the normal risk if one has a particular allele/genotype
What do BRCA1 and BRAC2 proteins do ?
Normally expressed in breast cells and other tissues, where they help repair damaged DNA or destroy cells if they cannot be replaced
What is BRAC2 ?
Human tumour suppressor gene
Where can the BRAC1 be detected ?
600kb region between markers on chromosome 17
