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Flashcards in Week 2 Deck (79)
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1
Q

What enzyme deficiency causes Gaucher Disease?

A

Glucocerobrosidases

2
Q

In gaucher disease, lipid accumulates predominantly in ___________

A

macrophages

3
Q

What is the likelihood of having a child at risk for Gaucher disease when both parents are affected with Gaucher?

A

100%

4
Q

Which therapy is currently used most frequently for patients with Gaucher disease?

A

Enzyme replacement therapy

5
Q

Which glycosphingolipids principally accumulates in Gaucher disease?

A

Glucocerebroside

6
Q

What type of Gaucher disease is non-neuropathic?

A

Type 1

7
Q

What could be a sign of a type of type I gaucher disease?

  1. Chronic Fever
  2. Jaundice
  3. Hepatosplenomegaly
  4. Headache
  5. Visual disturbances
A
  1. Hepatosplenomegaly
8
Q

Symptoms of gaucher disease can appear at…

A

ANY AGE - infancy, late adulthood, etc.

9
Q

Gaucher disease is diagnosed when levels of glucocerebrosidase activity are below normal at _____%

A

30%

10
Q

What is prevalence for type 1 Gaucher carriers in Ashkenazi Jews?

A

1/15

11
Q

Characteristics of Complex Traits (5)

A

1) Incomplete Penetrance
2) Variable Expressivity
3) Allele Heterogeneity
4) Locus Heterogeneity
5) Presence of Phenocopies

12
Q

Allele Heterogeneity

A

Several different mutations within one gene can cause the same disease

13
Q

Locus Heterogeneity

A

Mutations in several different genes can result in the same clinical presentation

14
Q

Phenocopy

A

environmentally caused phenotype that mimics the genetic version of the trait

15
Q

Multifactorial Inheritance

A

combination of genetic and non-genetic factors

  • Aggregate in families
  • Do not follow simple Mendelian mode of inheritance
  • EX) Cancers, Type 1 and 2 Diabetes, Alzheimer’s
16
Q

Determining Importance of Genetic vs. non-genetic factors via ________, ________, and _________ studies

A

Twin, Adoption, and Immigration studies

17
Q

Heritability

A

proportion of variance in trait that is due to genetic variation

18
Q

Genetic Association Studies (2)

A

1) Candidate Gene Association Studies

2) Genome wide association study

19
Q

Candidate Gene Association Studies

A

Studies gene directly

  • Relies on a priori biological hypothesis or positional hypothesis
  • BUT most a priori hypotheses are wrong → ALMOST ALWAYS yields false positives
  • Compare Allele frequencies in cases vs. controls
20
Q

Weaknesses of Candidate Gene Association Studies are ___________ and __________ almost always yielding _____________

A

Publication bias and population stratification

false positives

21
Q

Genome Wide Association study

A

case-control association study, but tests hundreds of thousands/millions of marker SNPs across the ENTIRE genome

22
Q

Weaknesses of Genome Wide Association studies are _________, __________, and __________

A

Population stratification
Lots of follow up
big sample size

23
Q

Strengths of Genome Wide Association studies are __________, __________, and __________ and are best used for ______________ with ________ effect sizes

A
  • no publication bias
  • can discover new genes (no prior hypothesis required)
  • Fine localization

Best for common alleles with small-moderate effect sizes

24
Q

Genetic Linkage Study

A

Search genome for segments disproportionately co-inherited along with disease in “multiplex families”

25
Q

Genetic linkage analysis measures ____________ and uses ________ the statistical measure of linkage

A

likelihood of recombination between two loci in meiosis based on genetic distance

Log of Odds (LOD)

26
Q

If LOD is > 3.0 then…

A

proof of linkage/gene localization

27
Q

1cM (centiMorgan) = ____% recombination between two ______ per ______

A

1%

loci per meiosis

28
Q

Strengths of Genetic Linkage studies are _______ and ________, and are best for _________ with ______ effect

A
  • can discover new, unknown genes
  • can provide fine localization

best for Mendelian traits (uncommon alleles with strong effects)

29
Q

A weakness of genetic linkage studies is that it isn’t good for ___________

A

complex traits

30
Q

Strength of Exome/Genome Sequencing Study

A

can get big snapshot of a person’s entire genome sequence

31
Q

Weaknesses of Exome/Genome Sequencing Studies include _______, _______, and ______.

A
  • difficult to distinguish between causal variants and non-pathological variation
  • requires follow-up analysis
  • Data interpretation difficult (variant of unknown significance, VUS)
32
Q

3 most commonly used DNA polymorphisms for finding genes

A

1) Microsatellites
2) SNPs
3) Copy Number Variants

33
Q

Microsatellites

A

Simple sequence repeats
multi-allelic

used in forensics

34
Q

Single Nucleotide Polymorphisms (SNPs)

A

Single NT change

35
Q

Haplotype

A

local context surrounding SNPs

36
Q

Copy number variants

A

common genomic deletions/insertions hundreds to tens of thousands of nucleotides in size

  • Tens of thousands known
  • Most not causal for human disease
37
Q

Compound Heterozygote

A

an individual who carries two different mutant alleles of the same gene

38
Q

Alpha Globin Gene Cluster: order of genes 5’–>3’ (spatial = temporal order of expression)

Located on chromosome ____ and has ____ copies

A

Zeta-Alpha2-Alpha1

2 copies on chromosome 16

39
Q

Beta Globin Gene Cluster:
order of genes 5’–>3’ (spatial = temporal order of expression)

Located on chromosome ____ and has _____ copies

A

Epsilon-Gamma-Delta-Beta

1 copy on chromosome 11

40
Q

HbF

A

apha2gamma2

41
Q

Adult Hemoglobins:

A

1) HbA: a2B2 (97%)

2) HbA2: a2d2 (2%)

42
Q

Qualitative Hemoglobinopathies

A

structural variants, normal synthesis but altered globin property
-HbS, HbC, HbKempsey, HbKansas

43
Q

Trinucleotide Repeat Disorders what are they, and what are 3 characteristics

A
  • Expansion of a segment of DNA consisting of three or more nucleotides
    1) Slipped Mispairing
    2) Genetic Anticipation
    3) Parental Transmission Bias
44
Q

Slipped Mispairing

A

mispairing of bases in regions of repetitive DNA coupled with inadequate DNA repair systems
-Longer repeat → more chance of subsequent mispairing

45
Q

Genetic Anticipation

A

Severity and/or onset of disease increases in the next generation (usually due to lengthening of repeat)

46
Q

Parental Transmission Bias

A

repeat expansion more prone to occur in gametogenesis of the male or the female

47
Q

Unique characteristics of mitochondrial inheritance (4)

A

1) Inheritance only through maternal lines
2) Affected males do NO pass on the genes
3) Replicative segregation
4) Heteroplasmy

48
Q

Replicative Segregation

A
  • At cell division, multiple copies of mtDNA replicate and sort randomly among newly synthesized mitochondria
  • This could be normal or mutated DNA
49
Q

Heteroplasmy

A

presence of more than one type of organellar genome within a cell or individual

50
Q

X chromosomal inactivation is typically ________ somatic cells of females and occurs _________.
Females are therefore _____________

A

random
in the first week of embryogenesis

mosaic for their X chromosome

51
Q

Mechanism for X inactivation

A

1) XIST gene expressed by inactive X chromosome (RNA expressed that coats inactivated X)
2) methylation of promoter regions prevents transcription

52
Q

NonRandom X inactivation occurs when __________

A

there is a structurally abnormal X chromosome

53
Q

If there is a:

1) abnormal X chromosome
2) Balanced translocation (involving X)
3) Unbalanced translocation (involving X)

THEN non-random inactivation of…

A

1) Abnormal X chromosome → non-random inactivation of abnormal X chromosome
2) Balanced translocation between X and autosome → non-random inactivation of NORMAL X, this preserves the balance
3) Unbalanced translocation between X and autosome→ nonrandom inactivation of der (X) and activation of the normal X

54
Q

4 Characteristics of epigenetics

A

1) Different gene expression pattern/phenotype from an identical genome
2) Inheritance through cell division, even through generations
3) Like a switch: ON/OFF
4) Erase-able (inter-convertible)

55
Q

Maintenance Methyltransferases

A

add methylation to newly synthesized strands, propogating epigenetic marks through somatic cell division

56
Q

Epigenetics: DNA methylation of CpG cytosines results in ________ but does not effect _________.

A

gene repression (locks cell in this state)

does not effect base pairing

57
Q

Epigenetics: Histone acetylation of chromatin results in ________ and is inherited because __________

A

gene activation

inherited because old histones influence new histones via enzymes to make new histones like the old ones

58
Q

Epigenetics: Histone Deacetylases act to _________ by _________.

A

silence genes

removing chemical groups from lysines

59
Q

TSG gene is typically ______ but can be silenced by _________. This is then stably maintained.

A

unmethylated/active

5meC causing aberrant methylation and silencing of tumor suppressor gene.

60
Q

4 mechanisms of genetic mutation leading to disease

A

1) Loss of function of protein (MOST COMMON)
2) Gain of function of protein
3) Novel property by mutant protein
4) Heterochronic expression (wrong time) or Ectopic expression (wrong place)

61
Q

Diagnostic Testing

A

Patient with signs or symptoms of genetic disease → positive genetic test result CONFIRMS diagnosis

62
Q

Predictive Testing

A
  • Patient with NO signs or symptoms of genetic disease → positive genetic test provides estimate of FUTURE disease risk
  • Some underlying risk of disease due to family history or ethnic background
63
Q

Informative results

A
  • Information from a genetic test DEFINITIVELY diagnoses or excludes the disease in question
  • Have family history of particular disease causing mutation, baby does NOT have mutation = informative
64
Q

Non-Informative Results

A
  • Situation where the genetic test result is normal, but it is not possible to definitively exclude disease/disease risk
  • No family history, particular mutation not found in baby = non-informative – multiple possible mutations
65
Q

Chromosomal Analysis tests for ________, and can only be used for _______ not ________

A

abnormality in chromosome number or structure

Used for BIG chromosomal changes (3-5Mb) and not for small scale issues

66
Q

FISH is used to detect ______ but before testing you must __________

A

200 Kb changes (duplications, deletions, translocations, copy number, aneuploidies)

know/strongly suspect diagnosis and what exactly you are looking for

67
Q

Sanger Sequencing/NextGen Sequencing is good for _________, but before testing you must _________. It cannot detect _________

A

small mutations or insertions/deletions

must know/suspect specific genetic diagnosis

cannot detect large deletions/insertions, rearrangements, etc.

68
Q

Microarrays (DNA based) can be used to identify ____________ but cannot diagnose __________

A

100-200Kb (aneuploidies, unbalanced chromosomal rearrangements, chromosome deletions/duplications, nucleotide)

Cannot diagnose: balanced chromosomal rearrangements, anything below 100-200 Kb, or nucleotide mutations

69
Q

3 Requirements of gene therapy:

A

1) Targeting: must be delivered/targeted to appropriate cells and NOT inappropriate cells
2) Expression: must lead to adequate expression and duration
3) Toxicity: side-effects must be acceptable

70
Q

Retroviral Gene therapy uses _________ and integrates into ____________. One issues is that you risk _________. Retroviruses are limited by ___________.

A
  • RNA viruses
  • cell genome of dividing cells (efficient)
  • risk insertional mutagenesis (can be passed on to daughter cells)

insert size (7-9kb max)

71
Q

Adenoviral Gene Therapy uses ________ and can infect _________. It does NOT ________, and therefore only has _______.
There is also a risk of ______

A

DNA viruses

  • any cell (not just actively dividing cells)
  • does NOT integrate into cell genome
  • transient expression
  • Severe immune reaction
72
Q

Non-viral gene therapy can use _____ .

It is good because it can have _________, _______, and ________, but is limited because it has _________ and _________.

A

direct DNA

large insertion sizes, minimal host response, and no risk of getting passed on to daughter cells

Limited because it has low efficiency and transient expression

73
Q

WNT4

A

-signaling factor for the development of ovaries

promotes female sex development and represses male sex development

74
Q

Mesonephric ducts develop into….

A

fallopian tubes

75
Q

Recombinant 8 syndrome

A

derives from parental carrier with balanced pericentric inversion 8 p23.1q22.1

76
Q

Severity of phenotype in mosaic down syndrome is related to…

A

the timing of mitotic non-disjunction event during development of zygote

77
Q

DNA methyltransferases and histone deacetylases could be used to treat…

A

anti-cancer therapy that disrupts inheritance of malignant epigenetic changes

78
Q

Chromatin state is maintained in what stage of the cell cycle?

A

S phase - during DNA replication

79
Q

DAX1 gene

A

SRY inhibitor