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Clinical Genetics Flashcards

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Biology 101 flashcards
1
Q

Amyloid Precursor Protein: percentage of EOAD? chrosomome?

A

10-15%. Chromosome 21.

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2
Q

Presenelin 1: percentage of EOAD? chromosome?

A

30-70%. Chromosome 14.

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3
Q

Presenelin 2: percentage of EOAD? chromosome?

A

5%. Chromosome 1.

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4
Q

Which early onset alzheimers disease gene do downs syndrome patients have an extra copy of?

A

Amyloid Precursor protein

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5
Q

What gene is implicated in late onset alzheimers?
What is the risk for hetero and homozygotes?
What chromosome is it on?

A

Apolipoprotein E (APOE)
Hetero: 3x inc risk. Homo: 10-30x inc risk.
Chromosome 19.

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6
Q 
What genes are implicated in schizophrenia?
on chromosome 1
on chromosome 6
chromosome 8
chromosome 22
A

DISC1
dysbindin
neuroregulin
COMT

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7
Q

What other condition is involved in chromosome 22?

What defects does such a person have?

A 
In digeorge/velocardiofacial disorder, chromosome 22 is deleted. 
Cleft palate
Abnormal facies
Thymic hyperplasia 
Cardiac abnormalities (Tetralogy of Fallot)
Hypocalcaemia/hypoparathyroidism
2
2
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8
Q

What base pairs pair up in DNA?

RNA?

A

Adenine - Thymine
Guanine - Cytosine
Swap Thymine for Uracil in RNA

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9
Q

In ADHD Heritability -
What is the number quoted for heritability?
Difference between males and females?
Two genes involved?

A

0.7-0.9 (74%)
No difference
DAT1, DRD4

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10
Q

Autism Heriability -
Siblings more likely? by what percentage?
mono twins concordance?
hetero twin concrodance ?

A

50-100% more likely
76%
34%

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11
Q

What gene is associated with FTD with Parkinsons?

A

MAPT

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12
Q

What gene is associated with CADASIL?

A

NOTCH3

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13
Q

What gene is associated with Huntingdon’s?

A

IL15 (Huntingdin gene)

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14
Q

What is the recombination fraction?

A

‘a measure of the distance between loci’

The recombination can vary from 0% if they are extremely close to 50% if they are on different chromosomes

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15
Q

What is LOD Score?

A

The LOD score (logarithm of the odds) is a method used to ascertain if there is evidence for linkage.

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16
Q

Name 4 Autosomal Dominant conditions.

Chance of child of affected parent getting it?

A 
Achondroplasia.
Huntingdons.
Neurofibromatosis.
Marfans.
50%

Neurofibromatosis type 1 and 2, tuberous sclerosis, achondroplasia, Huntington disease, Noonan’s syndrome

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17
Q

Name 3 Autosomal Recessive conditions.

A

Phenylketonuria
Wilsons
Homocystinuria

Phenylketonuria, homocystinuria, Hurler’s syndrome, galactosaemia, Tay-Sach’s disease, Friedrich’s ataxia, Wilson’s disease, cystic fibrosis

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18
Q

Name 2 conditions passed on by mitochondial

A

Leber’s hereditary optic neuropathy, Kearns-Sayre syndrome

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19
Q

X-Linked recessive

A

Cerebellar ataxia, Hunter’s syndrome, Lesch-Nyhan
Duchenne muscular dystrophy
Red green colour blindness
Hemophilia A and B

20
Q

X-Linked dominant

A

Vitamin D resistant rickets, Rett syndrome

21
Q

What chromosome is affected in Hungtingdons?
What decades usually affected?
EEG?
Chief path findings?

A

4
3rd and 4th decade of life
Flattened trace
Atrohpy of caudate and putamen (hence chorea), temporal lobe (hence memory issue), frontal (hence executive function)

22
Q 
Types of mutation meaning:
MISSENSE
Nonsense
Point 
Frame shift
Silent
A 
MISSENSE = new amino acid created
Nonsense = stop codon made
Point = simple change
Frame shift = insertion or deleiton
Silent = same amino acid made
23
Q

What conditions are affected by chromosome 1 issues?

A

Presenelin 1 gene (EOAD)

DISC1 (implicated in schizophrenia)

24
Q

What conditions are affected by chromosome 4 issues?

A

Huntingdons. CAG repeat.

Also Wolf-Hirschlon (4p; helmet warrior)

25
Q

What conditions are affected by chromosome 5 issues?

A

5p deletion (cri-du-chat)

26
Q

What conditions are affected by chromosome 9 issues?

A

Tuberose sclerosis

27
Q

What conditions are affected by chromosome 15 issues?

A 
Prader Wili (paternal)
Angelmans (maternal)
displaying genomic imprinting
28
Q

What does heritability mean?

A

Heritability is the proportion of phenotypic variance attributable to genetic variance. This means that if a condition has a heritability of 0.80 then 80% of the variance of that condition seen in a population is attributable to genetic variation. The remaining 20% is attributable to environmental factors.

29
Q

What are the top three and bottom three for heritability?

A

Bipolar 90
Autism 90
Schizophrenia 85
ADHD 80

Anorexia 55
Alcohol dependence 50
Depression 35

30
Q

What tauopathies do you know

A

Alzheimer’s
Pick’s (frontotemporal dementia)
Progressive supranuclear palsy
Cortiocobasal degeneration

31
Q

What chromosome codes for tau?

A

Chromosome 17

32
Q 
What is the trinucleotide repeat present in Huntingdons?
Normally how many times repeated?
What decade does disease manifest?
EEG?
Macroscopic findings?
A

CAG
Usually less than 27 times
Usually 3rd or 4th decades but can be earlier if more repeats
Flattened trace
Atrophy in caudate/putamen (hence chorea), frontal lobe (hence executive function issues), temporal regions (hence memory impairment)

33
Q

What term terms disorders with trinucleotide repeat disorders?
What conditions meet this?

A

Dynamic.

Huntingdons, spinocerebellar ataxia- CAG
Myotonic dystrophy CTG
Fredreichs ataxia (GAA)
Fragile X CGG

34
Q

Go through the stages of mitosis (cell division)

A

Interphase:
Gap 1
S phase (synthesis of DNA/DNA replication)
Gap 2

Mitotis:
Prophase - Chromatin condenses and becomes visible as chromosomes
Prometaphase - The nuclear membrane dissolves and microtubules become attached to the centromeres
Metaphase - Chromosomes become aligned at the middle of the cell
Anaphase - Paired chromosomes separate and begin moving to opposite ends of the cell
Telophase - Chromatids arrive at opposite poles of the cell and new nuclear membranes begin to form around them
Cytokinesis - The cell splits into two daughter cells each with a nucleus

35
Q

What is an endophenotype?

What criteria do they have to fulfill?

A

An endophenotype is a heritable marker for a condition that is invisible to the naked eye and relies on some form of laboratory measurement.

It is associated with illness in the population
It is heritable
It is state independent (present whether or not disease is present)
Within families, endophenotype and illness co-segregate (the endophenotype is more prevalent among ill relatives of ill probands than healthy ones)
The endophenotype found in affected family members is found in non affected family members at a higher rate than in the general population.

36
Q

What is the Heidy-Weinberg Principle?

A

The Hardy-Weinberg Equation is used to predict the percent of a human population that may be heterozygous carriers of recessive alleles for certain genetic diseases.

No mutations must occur, so that new alleles do not enter the population.
No gene flow can occur (no migration of individuals into, or out of, the population).
Mating between individuals must be random ( individuals must pair by chance).
Population must be sufficiently large that no genetic drift (random chance) can cause the allele frequencies to change.
Differences in genotype do not confer disparate survival or reproductive success on an individual (no natural selection occurs).

37
Q

Fragile X vs Klinefelters

Big differences?

A

Fragile X
Passed on X chromosome
Elongated face, large ears, large testicles, hand flapping, shyness, and little eye contact

Klinefelters
extra X - XXY
infertile
Tend to be tall with small testicles. Typically introverted with poor social and school performance

38
Q

What is meiosis?

In what phase do you get genetic recombination?

A 
Meiosis is a special type of cell division necessary for sexual reproduction.
Prophase I (homologous recombination)
39
Q

In what condition do you get elfin like features?

A

Williams.

7q11 deletion

40
Q

Which are the purine bases?

The pyrimidine ones?

A

AG

CTU

41
Q

What type of pass down follows knights move inheritance?

What conditions come under this bracket?

A

X-Linked Recessive.
Duchenne muscular dystrophy
Red green colour blindness
Hemophilia A and B

42
Q

What is lyonisation?

A
  • To correct the imbalance of possibly getting two Xs from Mum, by way of the process called Lyonization (X-inactivation), females transcriptionally silence one of their two Xs.
  • The inactivated X chromosome, then condenses into a compact structure called a Barr body, which is maintained in a silent state.
43
Q

Give three traits of XYY individuals.

A
  • usually asymptomatic, not usually infertile
  • taller than average
  • usually have learning disability
44
Q

In Rett syndrome

  • what kind of inheritance?
  • give some characteristic features.
A

X linked dominant.
Chromosome 28.

Normal for the first 12 months. Regression and loss of skills from around 18 months onwards.
Hand-wringing movements are the most common feature.

45
Q

What kind of inheritance is also known as

  • Vertical
  • Horizontal
  • Knights move
A

Vertical: autosomal dominant
Horizontal: autosomal recessive
Knights move: x linked (recessive)

46
Q 
Heritability of schizoprhenia for:
Identical twins
Both parents have it
Fraternal twins
Children
Full sibling
Half sibling
Parents
General popilation
A 
Identical twins - 50%
Both parents - around 50%
fraternal twins - around 17%
children - around 13%
full sibling - around 9%
half sibling around 6%
parent around 6%

Genetics (11 decks)

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