Modes of Inheritance Flashcards
what are the M’s ?
- Mendelian (most important 1)
- Multifactorial (most important 2)
- iMprinting
- Mitochondrial
- Mosaicism
what is penetrance?
- The likelihood of having a disease if you have a gene mutation
- 100% penetrance means you will always get the disease if you have the mutation
what are mendelian disorders?
diseases that segregates (spread around) families in manner predected by Mendels law(basically was finding out that we had dominant and recessive genes and about how they came from parents )
= Essentially a disease that is predominantly caused by a change in a single gene
what are examples of mendelian inheritance?
-autosomal dominant
-autosomal recssive
-X-linked (mitochondrial = genes only inherited by mother)
what level of penetrance does mendelian disorders have?
high penetrance
what is multifactorial inheritance?
when more than 1 factor causes a trait or health problem, such as a birth defect or chronic illness. Genes can be a factor, but other things that aren’t genes can play a part, too e.g. Nutrition
what are mitochondrial genes?
genes that are inherited only from the mother
what are examples of non-mendelian inheritance?
- methylation
- imprinting
- mitochondrial inheritance
- mosaicism
autosomal dominant key points
-seen in all generations
-50% risk of affected child if affected parent
-severity variable
-males and female equally affected
autosomal recessive key points
-often only 1 generation affected
-1 in 4 risk of infected child if parent carriers
X-linked inheritance carriers?
female usually carrier of gene and pass onto male children
what is result for children of female carrier of x-linked disease?
-1/2 male children will be affected
-1/2 female will be carriers
what is result for children of male carrier of x-linked disease?
-all male children will be normal (no male-male transmission)
-all female will be carriers (as can only pass on affected x chromosome)
why can female carrier show only mild features of x-linked disease?
due to x-inactivation, part of affected gene could be inactivated so not as bad symptoms
what is pedigree chart symbol for miscarraige?
triangle
what is pedigree chart symbol for affected and not affected?
affected = filled in
non-affected = not filled in
in most rare diseases is genotype or environment more important?
genotype
what is a single nucleotide polymorphism (SNP)?
=alterations in DNA sequence that can effect not diseases like height, weight, hair colour, health factors etc -> these effects are still through gene function
how common are SNP’s ?
10 million- they’re every 100-300 base pairs and are each given a unique ID
what are copy number variations (CVN’s)?
= extra or missing stretches of DNA
=they can size from a few bases to millions
=deletions or duplications
how common are CNV’s?
=highly prevalant (chance of disease)
=over 1500 known ones
=12% of human genome variable
how high is penetrance for multifactorial disease?
low for just one mutation
what is effect of SNP’s?
most SNP’s have no effect
SNPs that do have an effect are expected to have smaller effects than a rare disease causing mutation (some polymorphisms can completely destroy a gene without causing disease)
what is methylation?
-when methyl group on end of cytosine (only happens when opposite guanine)
-it prevents transcription and key in gene regulation, switching genes on and off
-makes mutation more likely
-allows environment to affect genome
what is imprinting?
differences in gene expression depending on whether a gene is maternally or paternally inherited (some genes only work if you inherit them from mother/father)
->specific chromosomal regions contain imprinted gnes
