Lecture 2 Flashcards
What are the two main causes of mutations?
Endogenous mutations and mutagens
What is an endogenous mutation?
A mutation which is caused due to spontaneous errors in DNA replication and repair
What is a mutagen?
A chemical that enduces damage to damage to DNA causing mutations to occur
What are the three types disorders that can arise from mutations?
Single gene disorders
Chromosome disorders
Complex/multi factorial disorders
What are the 6 types of chromosomal mutations?
Translocations, Deletions, Inversions, Chromosome loss Chromosome duplication
What are the two classes of substitution mutations?
Transition mutations and transversion mutations
What is a transition mutation?
When a purine is exchanged for another purine (A with G), or a pyrimidine is exchanged with another pyrimidine (C with T)
What is a transversion substitute mutation?
When a purine is replaced by a pyrimidine or vice versa (A to C) or (G to T) etc
What is the hotspot that differs from theoretical predictions of transversions being more common?
A c to T mutation
What ate the three effect based classifications of substitution mutations?
Silent mutations,
Nonsense mutations,
Missense mutations
What is premature protein truncation?
When the effect of a mutation results in a stop codon appearing earlier than it should resulting a shortened protein that may or may not be functional
What are the two types of Missense mutations?
Conservative where a similar type of amino acid is replaced resulting in little effect on function
Non-conservative where the amino acid replaced is dissimilar so a serious effect on function can occur
Where are the three regions where pathogenic mutations occur?
The coding region
Areas affecting gene regulation
Mutations affecting RNA stability of splicing
What is a frame shift mutation?
When an insertion or deletion of a base pair results in a change in the reading frame usually causing premature truncation and severe deleterious effects
What are the three factors that affect the phenotype seen from a premature truncation?
The stability of the polypeptide product
The extent of truncation
The functional importance of the missing amino acids
What are the inheritance features of an autosomal recessive disease?
The carriers are asymptomatic, typically not seen in parents, males and females equally affected
Risk 1:4
What are the inheritance features of an Autosomal Dominant Disease?
Phenotype typically appears in every generation, Risk 1:2 at least one paretn will display the phenotype
What are the inheritance features of a recessive x-linked disease?
Sons only inherit this from the mother, A male will pass on condition to all daughters, the incidence of disease is much higher in males
Disease is milder in women due to random X inactivation
What are the inheritance features of a dominant x-linked disease?
Male parents have no affected sons but all daughters affected
Females typically have a less severe disease
More common for females to have the disease
What are the inheritance features of a Y linked dominant disease?
Disease can only pass from male to male
Only males are affected
All sons of affected male are affected
