Lecture - Genetics (Intro to Inheritance Risk Assessment) Flashcards
Overview:
- What is diagnosis usually based on?
- What does genotype do?
So diagnosis is usually based on the phenotype and genotype confirms the diagnosis or predicts the phenotype (like with Mendelian disorders)
Talking about family history and human genetic variation
- What two types of big and small things lead to variation?
- What are two types of the last type from above?
- Where - exons or ncRNA genes - does most of the pathology take place?
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So autosomes - how many copies of a gene are there usually? What does that mean about gene dosage? But often, can we make-do with one copy?
Moving onto sex chromosomes - since males only have one copy of the X, what is the term for this?
Buuuuuuut not all autosomal genes are present as a two etc. In some people, some genes can be lost or absent orrrrr what else can happen to the gene? (e.g. the olfactory receptors) - called CNV
Second para - homozygous
Phenotypes - just observing will mean you can what?
It’s like getting a clinical, biochemical read out. You can diagnose based on symptoms without having to look at genotype
What’s the difference between gene, allele and loci?
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Genotype:
- It is a description of what?
- Often the genotype is inferred from what?
- What is the term used when you have 2 identical alleles at a single locus?
- What term for 2 different alleles at a single locus?
- What about if you only have one allele? (Like X and Y in males)
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What’s dominant and recessive? Co-dominant?
So like, it is the property of the pedigree but it is dependent on the biology of alleles and their gene products.
Heterozygotes display the phenotype of the dominant allele
Recessive allele only are observed in homozygotes
I’m guessing this has to do with the gene dosage thing - with dominant alleles, they are fine just being one or two and the recessive doesn’t express or expressed very little?
Co-dominant is when both are expressed equally
If the disease is autosomal recessive (aa), then whats the chance of being a carrier?
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What’s the likelihood if kid being affected if the disease is autosomal dominant? What about autosomal recessive? What about consanguineous?
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X-linked recessive
- If you have carrier mothers, what happens to the sons?
- What percentage of sons affected?
X linked dominant
- What if affected father - who is affected?
- What if affected mother? What happens to the males?
Y linked - are there any significant diseases?
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Extensions of Mendelian inheritance:
- Mitochondrial inheritance
- it is inherited from the mother so m_____
- males and females are affected here
- there is variable expressivity so what’s the term for this? - Pseudo-dominance
- the phenotypic expression of a recessive allele as a result of…..
- or you can see this because you have a _____ recessive allele in pop
Heteroplasmy - A cell can have some mitochondria that have a mutation in the mtDNA and some that do not. This is termed heteroplasmy. The proportion of mutant mtDNA molecules determines both the penetrance and severity of expression of some diseases.
Homoplasmy refers to a cell that has a uniform collection of mtDNA: either completely normal mtDNA or completely mutant mtDNA.
Variable expressivity;
- Why is the phenotype variable between individuals who have the same phenotype?
- Extreme case of variable expressivity is non-penetrance - what does that meme?
- Probably because of environment and choices (lol, Anika)
- Penetrance = the extent to which a particular gene or set of genes is expressed in the phenotypes of individuals carrying it, measured by the proportion of carriers showing the characteristic phenotype.
So non-penetrance is called incomplete penetrance for a disorder (aka, it just doesn’t show up even If you have the genotype for it)
Triplet repeat expansions: Dynamic mutations
- They show anticipation - what is this?
- Why are they dynamic mutations?
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What are the two types of genetic heterogeneity?
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