Genetic disorders 1 Flashcards
Where are mutations causing heritable genetic diseases found?
The germline
What is the main difference between germline mutations and somatic mutations?
in germline mutations, it will affect all the cells in the organism whereas in somatic mutations it may only affect specific areas
Where in the genome do most disease causing mutations occur?
Exons
What is polyploidy?
Extra set of chromosomes
What can polyploidy be caused by?
nondisjunction
What is nondisjunction?
Failure of chromosomes to properly separate
What phase of mitosis/meiosis1 or 2 does nondisjunction occur during?
Anaphase
What is aneuploidy?
One single chromosome extra or missing
When does aneuploidy usually occur?
Egg production in meiosis
What can cause aneuploidy?
nondisjunction
What is a splice site mutation?
A change in the splice acceptor site, causing splicing to occur differently
What is the role of the splice acceptor site?
It signals to the spliceosome where the cut should be made
What is known about a disease if it needs both copies of a gene to mutate in order to manifest?
It is recessive
What is known about a disease if only one copy of a gene needs to mutate in order for it to manifest?
it is dominant
What is a dominant negative effect of a gene?
When the protein product of a mutated gene interferes with the protein product of the wild type gene
What is mendelian inheritance?
The situation when the presence of mutation in a single gene is sufficient for disease manifestation
What is locus heterogenity?
Mutations in one of multiple genes can cause the same phenotype
What is incomplete penetrance?
A mutation not causing a disease when otherwise expected
How could incomplete penetrance occur?
Although the gene has mutated, other factors that affect gene expression could come into play
What factors that affect gene expression could cause incomplete penetrance?
Genetic background and environment
What is genetic background?
Other genes effect on that specific gene
Who is mtDNA inherited from?
Mother
Why is mtDNA only inherited from the mother?
Mitochondria from the sperm doesnt enter the egg during fertilisation
How can siblings have varying degrees of severity of a mitchondrial disease?
If the mother only has some mutant mitochondria, different childeren will inherit different amounts of this and so have different disease severity?
What organs are most severely affected by mitochondrial diseases?
Brain and skeletal muscle
Why is the brain and skeletal muscle most affected by mitochondrial diseases?
High energy organs so require mitochondria the most
