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2020 MHS Genetics Unit2 > population genetics and non-mendelian inheritance > Flashcards

population genetics and non-mendelian inheritance Flashcards

1
Q

allows calculation of allele distribution in a population. Formulate the law and list the requirements

A

hardy-Weinberg law

  1. requirements
    1. population is large
    2. mating is random
    3. allele frequencies remain constatnt over time
      1. no selection against any genotype
      2. departing individuals from the population have similar allele frequencies than the original population
      3. there is no significant rate of new mutations in the population
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2
Q

In the hardy weinberg equation what does p and q stand for?

A

p always refers to the most common allele and q refers to the variant allele

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3
Q

describe the conditions used in the hardy weingberg calculation for autosomal recessive diseases

A
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4
Q

describe the conditions used in the hardy weinberg calculation for an autosomal dominant disease

A
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5
Q

describe the conditions used in the hardy weinberg calculation for an X-linked recessive disease

A
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6
Q

describe the condtions used in the hardy weinberg calculation for X-linked dominant diseases

A
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7
Q

formulate the probability calculations using population frequencies

A
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8
Q

What are the two requirements for hardy weingberg and what are the 7 violations? (just list them)

A
  1. violation of random mating
    1. stratification
    2. assortive mating
    3. consaguinity and inbreeding
  2. violation of the constatnt allele frequency criteria
    1. impaired reproductive fitness
    2. genetic drift
    3. migration and gene flow
    4. heterozygote advantage
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9
Q

African americans have a greater frequency for sickle cell because of mate selection to stay with in a sub group.

Does this deviate from hardy weinberg and how?

A

Yes it does

  1. STRATIFICATION
    1. ​subgroups in a population tend to mater within the subgroup
    2. African american mate with eachother in the american population
  2. violates the random mating in large population criteria
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10
Q

Many people marry and multiply due to religous reasons.

Does this deviate from hardy weinberg and how?

A

yes it does,

consaguinity and inbreeding

  1. mating between related individuals
  2. mating within genetic isolates
    1. ​cultural
    2. geographical
    3. religous
  3. violates the random mating in large population criteria
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11
Q

two people seek eachother out on facebook and end up together because they both have a condition called anchondroplasia.

Does this deviate from hardy weinberg and how?

A

yes it does,

  1. choice of the mate i based on a particular trait
  2. marry and mate because they have similar physical traits
  3. violation of the random mating in large population criteria
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12
Q

a population is large and there is a random mating.

Does this deviate from hardy weinberg and how?

A

no, this is one of the two requirements for the hardy weinberg equation

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13
Q

a klinfelter patient can marry but is unable to continue his lineage.

Does this deviate from hardy weinberg and how?

A

yes it does,

impaired reproductive fitness

  1. the variant allele causes infertility, reduced fertility or death before reproductive age
  2. violation of the constatnt allele frequency criteria
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14
Q

a small population has a change in allele frequency.

Does this deviate from hardy weinberg and how?

A

yes it does,

genetic drift- random(non genetic) changes

  1. violation of the constant allele frequency criteria
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15
Q

a group of main islanders move to an isolated island and live there for 100 generations. These people are well known for their

Does this deviate from hardy weinberg and how?

A

yes it does,

genetic drift- founder effect

  1. a small subpopulation breaks off from a larger one and by chance carries a variant allele in higher frequencies
  2. violation of the constant allele frequency criteria
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16
Q

the spanards expolrers moved from spain to mexico and mated with the locals of the land.

Does this deviate from hardy weinberg and how?

A

yes it does,

migration and gene flow

  1. changing of allele frequencis in mixing populations
  2. violation of the constant allele freuency criteria
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17
Q

in Africa bein heterozygous for sickle cell will not generate the debilitating symptoms of sickle cell and you are resistant to malaria.

Does this deviate from hardy weinberg and how?

A

yes it does,

heterozygote advantage

  1. positive evolutionary selection for heterozygote genotype
  2. in the example
    1. homozygous wild-type
      1. susceptible to malaria
    2. homozygous variant allele
      1. sickle cell disease
    3. heterozygous
      1. do not have sickle cell disease and are protected from malaria
  3. violation of the constatnt allele frequency criteria
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18
Q

only one parental allele is active

what type of inheritance pattern is this?

A

genomic imprinting

  1. only one parental allele is active
  2. allele activity depends on the origin of the allele
  3. takes place in the germ line
  4. initiated by and imprinting center and involves the generation of non-coding RNAs and chromatin changes
  5. can be tissue specific
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19
Q

the variant allele changes from generation to generation.

what type of inheritance pattern is this?

A

unstable repeat expansion

  1. the bariant allele changes from generation to generation
    1. tinucleotide sequences multiply
  2. disease exmaples
    1. huntingtons disease
      1. larger the repeat number = earlier onset
    2. fragile x syndrome
      1. excessive CGG repeats in the promoter of the FMR1 gene = intellectual disability
    3. friedreich ataxia
      1. excessive GAA = spinocerebeller ataxia
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20
Q

the father cannot pass his mtDNA down.

what type of inheritance pattern is this?

A

inheritance of mitochondrial DNA

  1. only the maternal mitochondrial DNA is inherited
  2. maternal mitochondria are randomly distribute to the daughter cells
    1. homoplasmy - cells with mutatnt mtDNA
    2. heteroplasmy - cells with both normal and mutant
  3. diseases- phenotype dependent on ratio. have reduced penetrance and variable expression
    1. OXPHOS = leber hereditary optic neuropathy (NADH reductase deficiency
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21
Q

Describe the imprinting process for chromosome 15

A
  1. the paternal IC generates a long _polycistronic RNA_that _silences_ the paternal _UBE3A_ expression in neurons (tissue specific)
  2. the maternal IC** is **silenced and cannot generate the polycistronic RNA, so the materna lUBE3A is not silenced
  3. UBE3A** is only **expressed from the maternal allele in neurons
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22
Q

A patient presents a deletion in the maternal chromosome 15. what is the disease and what is the loss of function?

A

Angelman syndrom

  1. deletion in the maternal chromosome 15
  2. loss of UBE3A function
  3. presentation
    1. intellectual disability
    2. happy demeanor
    3. balance disorder
    4. speech impariment
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23
Q

a patient presents with a deletion in the paternal chromosome 15.

A

prader-willi syndrome

  1. deletion in the paternal chromosome 15
  2. loss of the polycistronic RNA or other genes
  3. presentation
    1. intellectual disability
    2. obesity
    3. short stature
    4. hypodonadism
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24
Q

loss of UBE3A function

what is the disease and cause?

A

angelman syndrome

  1. deletion in the maternal chromosome 15
  2. loss of maternal UBE3A
    1. the two c’somes
      1. the maternal UBE3A is the only chromosome that can express this gene
      2. The paternal generates a polycistronic RNA that silences the paternal
    2. the maternal is deleted and paternal is silenced (naturally) = no expression in UBE3A
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25
Q

loss of the polycistronic RNA or other genes.

What is the disease and the cause?

A

prader-willi syndrome.

  1. deletion in the paternal chromosome 15
  2. loss of the polycistronic RNA and other genes
    1. two c’somes
      1. the maternal UBE3A is the only chromosome that can express this gene
      2. The paternal generates a polycistronic RNA that silences the paternal
    2. the UBE3A is tissue specific, so with out the expression level in some tissue, prader-willi syndrome manifests
26
Q

what arethe three causes of angelman syndrom or prader willi syndrome?

A

the basis of these two diseases revolves around c’some 15.

angelman=loss maternal

prader-willi syndrome = loss of paternal

  1. causes
    1. uniparental disomy
    2. IC mutations
    3. UBE3A or polycistronic RNA mutations
27
Q

what are the three diseases to know for unstable repeat expansion?

  1. disease
    1. repeat
    2. inheritance
A
  1. huntingtons
    1. CAG repeats
    2. autosomal dominant
  2. fragile X syndrom
    1. CGG - promoter of FMR1 gene
    2. Xlinked dominant
  3. friedreich ataxia
    1. GAA repeats - intron of the frataxin gene
    2. autosomal recessive
28
Q

autosomal dominant neurodegenerative disorder

A

Huntington disease

  1. polyglutamine disorder
  2. more CAG repeats = higher younger symptoms appear
  3. 29-35 premutation range
29
Q

what is this pedigree exhibiting?

A

larger the repeat number is the earlier the onset of the disease is.

CAG repeats alter the function of the protein

30
Q

x linked dominant

moderate intellect disability

  1. disease
  2. cause
  3. repeats explaination
A
  1. fragile x syndrome
  2. c chromosome condensation effect
    1. caused by excessive CGG repeats in the promoter of the FMR1 gene and silences the gene
      1. FMR1 is a translational regulator in neurons
  3. repeats
    1. normal
      1. up to 55
    2. premutation
      1. 55 -200
    3. affected
    4. >200, can be several thousand
31
Q

autosomal recessive

incoordination of limb movement

  1. disease
  2. cause
  3. repeat explaination
A
  1. friedreich ataxia
  2. excessive GAA repeats in an intron of the frataxin gene
    1. frataxin is a mitochondrial protein involved iron metabolis
    2. impairs transcirptional elongation
  3. repeats explained
    1. normal repeat
      1. 2-33
    2. premutaion
      1. 34-65
    3. affected
      1. 66-1200
32
Q

homoplasmy

A

if a cell only contains mitochondria with mutant DNA

33
Q

heteroplasmy

A

if a cell contains mitochondria with bot h normal and mutans DNAs

34
Q

how can a mitochondrial disease have reduced penetrance and variable expression?

A
  1. only the maternal mitochondiral DNA is inherited
  2. maternal mitochondria are randomly distributed to the daughter cells
  3. homo vs heteroplasmy
  4. the expression of a disease phenotype depends on the ratio of the normal and mutant mtDNA
35
Q

what disease is associated with this type of pedigree? Why?

A

mitchondrial disease

  1. ONLY FEMALES TRANSMIT THE DISEASE
    1. differenciate this from X linked and Xlinked dominant (see photo)
  2. a heteroplasmic mother will pass the disease to ALL OF HER CHILDREN**, but the **expressivity of the disease will vary amound the children
    1. depending on the tissue distribution of the mutant mtDNA
  3. example
    1. OXPHOS diseases
      1. leber hereditary optic neuropathy (NADH reductase deficiency
        1. causes loss of vision
36
Q

LHON has what type of inheritance?

A

OXPHOS diseases such as Leber Hereditary Optic Neuropathy (NADH reductase deficiency - causes optic atrophy

37
Q

multiple genes and environment factors cause the disease

A

multifactorial diseases

  1. susceptibility genes
    1. genes that are associated with multifactorial disease
  2. do not follow classical mendelian inheritance
38
Q

what is this inheritance associated with?

A

this is a disease with an complex inheritance

39
Q

the individual either has the disease or not

A

qualitative trait

40
Q

measurable parameters that associate withe the disease

  1. blood pressure
  2. body mass index
  3. cholesterol level
A

quantitative traits

41
Q

what does familar aggregation lead to? Why?

A
  1. familiar aggreation
    1. diseases with multifactorial inheritance frequently cluster in families
    2. due to sharing
      1. genetic material with in family
      2. enviornment with the family
42
Q

when two related individuals have the same disease

A

concordant for a disease = 2 related individuals have the same disease

43
Q

2 related individuals do not have the same disease

A

discordant for the disease

  1. 2 related individuals do not have the same disease are discordant for the diseased
44
Q

it is a measure for the familiar aggregation of the qualitative trait

A

Relative risk

  1. measures for the familiar aggregation of the qualitative trait
    1. for the occurrence of the disease
      2.
45
Q

what is the formula to measure the relative risk?

46
Q

explain what it means to have a relative risk for autism of 150

A

if you have a sibling affected with autism you are 150 times more likely to have it

47
Q

has identical genetic material

A

monozygotic twins (MZ) has identical genetic material (almost)

48
Q

in avergae 50% of alleles in common

A

Dizygotic twins (DZ) have, in average 50% of their alleles in common

49
Q

concordance between MZ twins indicates contribution of _______ factors.

A

Less than 100% concordance between MZ twins indicates the contribution of enviornmental factors.

50
Q

what does it mean when MZ has a higher concordance than DZ?

A

When MZ concordance is higher than DZ concordance, the disease has a genetic component )especially for early onset diseases)

51
Q

multifactorial diseases have four key features

A
  1. genes contribute but the disease does not follow mendelian inheritance
  2. diseases often demonstrate familial aggregation
  3. relatives can be discordant even if they share susceptibility genes
  4. the disease is more common among close relatives and less common in less closely related relatives
52
Q

what do the following diseases have in common?

  1. venous thrombosis
  2. Type 1 diabetes mellitus
  3. coronary artery disease
  4. late-onset alzheimer disease
  5. lung cancer
A

multifactorial diseases

53
Q

excessive blood clot formation

  1. disease
  2. cause
  3. result
A
  1. disease
    1. venous thrombosis
  2. cause
    1. gain of function mutations from enviornment factors
      1. oracl contrceptives(estrogen containing), smoking, prolonged inactivity and trauma
    2. FActor 5 and Prothrombin
  3. result
    1. heterozygous vs homozygous
54
Q

autoimmune destruction of pancreatic beta cells

  1. disease
  2. cause
  3. result
A
  1. disease
    1. Type 1 diabetes mellitus
  2. cause
    1. autoimmune destruction of pancreatic beta cells, which leads to insulin
    2. susceptibility genes are respondible for producing cell surface
      1. MHC complex loci (HLA-DR)
    3. environmental
      1. early viral infections
      2. exposure to cows milk?
  3. result
    1. destruction of pancreatic beta cells
55
Q

what has the highes trisk for development of Typ1 diabetes?

56
Q

formation of atheroscelrotic plaques

  1. disease
  2. cause
  3. result
A
  1. disease
    1. coronary artery disease
  2. cause
    1. susceptible genes
      1. apopliproproteins
      2. LDL receptor
      3. coagulation factors
      4. angiotensin converting enzyme
    2. enviornmental factors
      1. diet
      2. smoking
      3. lack of physical activity
    3. multifactorial disorders
      1. hypertension
      2. obesity
      3. diabetes
  3. result
    1. formation of atheroscletoric plaques in arteries that eventually can cause blood clot formation and myocardial infarction
57
Q

multifactorial disorder such as hypertension, obesity and diabetes can generate

A

coronary artery disease

58
Q

caused by beta-amyloid precipitation in the brain

  1. disease
  2. cause
  3. result
A
  1. disease
    1. late-onset alzheimer disease
  2. cause
    1. beta amyloid precipitation in the brain
    2. susceptibility gene
      1. apolipoprotien E (epsilon4 isoform)
        1. apoE is present in the amyloid precipitates
    3. risk factor
      1. age
      2. sex-more frequent in females
      3. brain injurry
  3. result
    1. late onset alzheimer disease from beta plaque deposits
59
Q

aryl hydrocarbon hydroxylase genes can be induced by?

  1. disease
  2. cause
  3. result
A
  1. disease
    1. lung cancer
  2. cause
    1. enviornmental risk factors
      1. cigarette smoke
    2. susceptibility genes
      1. aryl hydrocarbon hydroxylases
  3. result
    1. person specific-induced by cigarette smoke
      1. high inducibile aryl hydrocarbon hydroxylase alleles
        1. alleles produce more enzymes (aryl hydrocarbon hydroxylase), making more epoxides ->DNA damage
      2. low inducibility aryl hydrocarbon alleles
        1. less activation of the aryl hydroxylase enzymes and less epoxides ->less DNA damage
60
Q

what enzyme is associated with smokers who have manifested lung cancer?

2020 MHS Genetics Unit2 (5 decks)

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