Mendelian Inheritance / Pop. Genetics - Dr. Taylor L2 Flashcards Preview

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Flashcards in Mendelian Inheritance / Pop. Genetics - Dr. Taylor L2 Deck (20)
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0
Q

What are the four basic patterns of single-gene inheritance? (genes located in the nucleus)

A
  1. Dominant autosomal / pseudoautosomal
  2. Dominant X-linked
  3. Recessive autosomal / pseudoautosomal
  4. Recessive X-linked
1
Q

What is a pseudoautosomal locus?

A

locus located on the X chromosome that does not show X-linked inheritance pattern because it can recombine with counterparts on the Y chromosome

occurs in male meiosis

2
Q

Genes not located in the nucleus?

A

mitochondrial

3
Q

Define loss-of-function mutation

A

mutation that reduces or eliminates the function of a gene product

4
Q

Define co-dominant gene and give an example

A

two different alleles of a locus are expressed

ABO blood typing

5
Q

Define incompletely dominant

A

homozygotes more severely affected than heterozygotes
or
heterozygote phenotype is somewhere in between the two homozygotes

6
Q

Penetrance vs. Expressivity of a gene?

A

Penetrance: the probability that a gene will have a phenotypic expression (of any severity)

Expressivity: the severity of expression of a phenotype among individuals with the same disease-causing genotype

7
Q

Define age-dependent penetrance and the example given in the text.

A

Occurs when phenotype expression (all-or-none) varies with age.

Ex: Neurofibromatosis. Penetrance in newborns is <50%. Penetrance in adults is 100% Symptoms develop slowly throughout childhood.

8
Q

Congenital versus Genetic disease

A

Congenital is any disease present at birth

Genetic is any disease caused by a gene mutation

9
Q

Give some factors that obscure the (Mendelian) inheritance pattern in a pedigree.

A
Reduced penetrance
Variable Expressivity
Other genes
Environmental factors
Affected individuals not suriving to birth
Accuracy of information
New mutations
10
Q

Define genetic heterogeniety

A

Different mutations at the same locus (allelic heterogeneity) or
Mutations at different loci (locus heterogeneity) or
Both
All leading to the same disorder (i.e. not a really a single gene mutation)

11
Q

Define pleiotropy (this is a tough one… ;)

A

When a gene affects more than one organ system; causes multiple diverse symptoms

12
Q

What is the gene mutated in Wilson’s disease and give a few “classic” symptoms.

A

gene: ATP7B helps transfer excess copper into the blood stream and bile
symptoms: cirrhosis of the liver, neurological (psych. & movement disorder), Kayser-Fleischer rings

13
Q

Describe the Mitochondrial Inheritance pattern.

A
  1. Matrilineal Inheritance pattern (non-Mendelian)
  2. Homoplasmy and Heteroplasmy
  3. Replicative Segregation
14
Q

Distinguish between homoplasmy and heteroplasmy.

A
  1. homoplasmic female will pass it on to ALL her children; equal severity of disease among offspring
  2. heteroplasmic female will pass it on to ALL her children; the fraction of mutant mitochondria (and thus severity/symptoms) in offspring will vary
15
Q

What is a modifier gene?

A

Genetic factor outside the disease-causing locus that still affects the expression of the Mendelian disease.

16
Q

What is a phenocopy?

A

Disease due to non-genetic factor. e.g. environment or other factors cause a mutation which in turn causes a disease.

ex: radiation exposure –> thyroid cancer

17
Q

What are stochastic effects?

A

Randomness giving rise to disease.

18
Q

What is acute intermittent porphyria?

A

Genetic disease that manifests in response to “exposures”
Autosomal Dominant
In the heme production pathway, a deficiency of porphobillinogen deaminase (enzyme) causes pathway to stall and a buildup of porphobilinogen (intermediate) in the cytoplasm.

19
Q

Sex Influence and Sex Limitation of genetic diseases?

A

Sex Influence: condition is more common in one sex than the other. ex: gout more common in males

Sex Limitation: only one sex can express a disease. ex: prostate cancer