Non-Mendelian Inheritance Flashcards
What is non-mendelian inheritance?
General terms the refers to any pattern of inheritance in which traits do not segregate in accordance with Mendels laws
These laws describe the inheritance of traits linked to single genes on chromosomes in the nucleus
What are CNVs?
Copy number variations - extra of missing stretches of DNA - deletions or duplications
In CF for example what is the contribution of genetic and environmental factors?
Very little environmental and huge amount of genetic
What disease has a 100% penetrance?
Achondroplasia
What is penetrance?
Likelihood of having the disease if you have the mutation
What is a Mendelian disorder?
One which is controlled by a single locus, mutation in a single gene causes the disease
What is a multifactorial disorder?
Does not have a single cause, associated with the effects of multiple genes in combination with lifestyle and environmental factors.
Describe penetrance in Mendelian disorders
High penetrance
Small environmental contribution
Describe penetrance in multifactorial disease?
A genetic change is just another risk factor
Penetrance for any one mutation is low
Heart diseases is more common in _____ degree relative of affected individuals
Heart diseases is more common in first degree relative of affected individuals
What percentage of genes do monozygotic and dizygotic twins share?
Mono - 100%
Di - 50%
What does P<0.05 mean in a statistical test ?
There is a 1 in 20 probability that the data you see
has happened by chance
What is a risk model?
An equation that ties together different risk factors and gives you a risk prediction for your patient
Name 3 other non-mendelian inheritance patterns
Epigenetic modification of DNA
Mitochondrial inheritance
Somatic mosaicism
What is DNA methylation?
DNA methylation is an epigenetic mechanism used by cells to control gene expression. … DNA methylation refers to the addition of a methyl (CH3) group to the DNA strand itself, often to the fifth carbon atom of a cytosine ring.
Describe some more about DNA methylation?
It occurs on the cytosine base just before guanine, usually ending up with methyl CG.
Methylation can effect interactions with histones etc, making DNA now hard (instead of easy) to transcribe
What is the clinical importance of DNA methylation?
Abnormalities of methylation causes genetic disease
Methylation causes gene silencing in cancer
What is imprinting?
Differences in gene expression depending on whether a gene is maternally or paternally inherited.
Variation in gene expression depending on
which parent you inherit the gene from
What happens if the allel from the father is imprinted?
It will be silenced and only the mother allel will be expressed
Give some symptoms of Angelman Syndrome?
Neuro genetic disorder Developmental delay Intellectual disability Ataxia Epilepsy Happy demeanor Frequent laughing and smiling
Why does angelman syndrome happen?
If you dont have a working cop of the UBE3A gene which is on chromosome 15.
UBE3A only works in the copy you get from your mother.
The copy from your father is methylated
Roughly what is Paternal Uniparental Disomy?
When you get both copies of chromosomes from one parent, and one from the other parent, you loose that one, so have both from the one parent. Which have diseases and so you get disease…
Where else do you keep DNA?
Mitochondrial DNA
Describe Mitochondrial DNA?
Many copies (because of many mitochondria) in a cell Contains important genes for mitochondrial metabolic pathways and ribosomal RNAs Inherited almost exclusively maternally Point mutations and deletions occur
