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(D) MOD > Lecture 9: Clinical Genetics > Flashcards

Lecture 9: Clinical Genetics Flashcards

1
Q

What is a locus?

A

Position of a gene on a chromosome.

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2
Q

What is an allele?

A

A series of 2+ genes occupying same location of a chromosome.

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3
Q

What are the mendelian patterns of inheritance?

A

Autosomal dominant
Autosomal recessive
Sex-linked

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4
Q

What is XY and XX? What does it mean phenotypically? What is important about the Y?

A

X is inherently female.
Y is what gives male characteristics, so lack of Y = female.

XX is phenotypically female
XY is phenotypically male

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5
Q

Which sex chromosome is bigger?

A

X

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6
Q

Where do males get their X from?

A

Mother only

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7
Q

What is the key characteristic of an autosomal dominant disorder?

A

An affected person usually has at least one affected parent.

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8
Q

What are 2 examples an autosomal dominant disorder?

A

Huntington’s Disease: degenerative nerve disease from mutation in HTT gene
Marfan syndrome: degenerative connective tissue from mutation in FBN1 gene (prevents elastic fibers forming around connective tissue)

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9
Q

What is the key characteristic of an autosomal recessive disorder?

A

Males and females are equally affected.

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10
Q

What are 2 examples of an autosomal recessive disorder?

A

Cystic Fibrosis: mutation of CFTR, dysregulation of salts inc mucous
Sickle Cell: mutation of HBB gene, mutation in hemoglobin misshapen RBC

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11
Q

What are the key characteristic of an X-linked recessive disorder?

A

Usually affects males and all daughters of an affected male are carriers.

Females are affected only if father is affected and mother is at least a carrier.

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12
Q

What are 2 examples of X-linked recessive disorders?

A

color blindness, hemophilia

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13
Q

What are the key characteristics of an X-linked dominant disorder?

A

Very rare

Similar pedigree to autosomal dominant BUT no male to male transmission.

Note: This is because males can’t contribute an X. They only give a Y to a male.

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14
Q

What is an example of an X-linked dominant disorder?

A

rett syndrome: mutation in MECP2- early neurodevelopment disorder

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15
Q

What are the key characteristics of a Y-linked disorder?

A

ONLY MALE TO MALE

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16
Q

What is an example of a Y-linked disorder?

A

hypertrichosis

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17
Q

What are the key characteristics of a mitochondrial disorder?

A

Can affect both sexes, but only an affected mother can transmit it.

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18
Q

What is a disorder with mitochondrial DNA?

A

Leber’s Hereditary optic neuropathy: sudden vision loss around age 20, lack of mitochondria leads to cell death

(myopathy or neurological problems)

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19
Q

What is a polygenic trait?

A

A trait involving multiple alleles at different loci that affect a phenotype.

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20
Q

What is multifactorial inheritance?

A

Interaction between genes and environment.

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21
Q

What is penetrance for genetics?

A

% of individual with a given genotype that exhibit the phenotype.

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22
Q

What is nonpenetrance?

A

Failure of a phenotype to manifest even with a given genotype. (makes risk assessment hard since phenotype can skip a generation)

23
Q

What is expressivity?

A

The extent to which a given genotype is expressed at the phenotypic level.

Note: You can have variable expressivity in the same family.

24
Q

What causes expressivity?

A

Modifier genes

25
Q

What is anticipation?

A

Specific type of variable expressivity caused by instability of triplet microsatellite repeat regions.

Note: With successive generations, age of onset decreases and severity worsens.

26
Q

What is the difference between penetrance and expressivity?

A

Penetrance is whether a traits appears at all (either yes or no)

Expressivity is the degree to which a trait appears (sliding scale)

27
Q

When do congenital disorders most commonly occur?

A

Embryonic period, which is weeks 3-8.

28
Q

What are the four kinds of morphologic deficits?

A

Congenital malformations
Congenital deformations
Congenital disruptions
Congenital dysplasia

29
Q

What is a congenital malformation?

A

Physical deficits due to INTRINSICALLY ABNORMAL DEVELOPMENT PROCESS

Example: Spina bifida, cleft lip/palate, neural tube defects

30
Q

What is a congenital deformation?

A

Abnormal form or position of a body region caused by NON DISRUPTIVE MECHANICAL FORCE

Example: clubfoot, congenital hip defects

31
Q

What is a congenital disruption?

A

A structural abnormality due to A DESTRUCTIVE FORCE

Example: Missing digits secondary to an amniotic band

32
Q

What is a congenital dysplasia?

A

Abnormal growth or development of a tissue or organ

Example: Development dysplasia of the hip

33
Q

What are teratogens?

A

Agents that can cause abnormalities during embryonic/fetal development.

34
Q

What medication characteristics make them more likely to affect a fetus?

A

More lipophilic and low molecular weight drugs.

35
Q

What is fetal alcohol syndrome? Characteristics?

A

Facial abnormalities: smooth philtrum, thin upper lip, small palpebral fissures
Growth deficit (< 10th percentile)
CNS abnormalities (small head, cognitive deficits, motor delays, attention deficits)

36
Q

What are TORCH infections?

A

Toxoplasmosis
Other
Rubella
Cytomegalovirus (CMV)
Herpes

Other - varicella, listeriosis, leptospirosis, EBV, TB, Syphilis, HIV, parvovirus B19

37
Q

What is congenital zika syndrome indicated by?

A

Severe microcephaly,
decreased brain tissue
retinal damage
limited ROM in joints
increased muscle tone

Note: Small brain, big muscles

38
Q

What is the concern with ionizing radiation?

A

Pregnant people who get HEAVY doses.

39
Q

What are the maternal metabolic diseases?

A

Diabetes
Folic acid deficiency
Hypothyroidism

40
Q

What are some types of pre-conception screening?

A

Family history with pedigree
Carrier testing via DNA sequencing
Karyotype testing

41
Q

What are some types of post-conception screening?

A

Ultrasound
Nuchal translucency
Cell-free DNA
Quad screening of AFP, hCG, inhibin A, unconjugated estradiol

42
Q

What are some types of prenatal diagnostic testing?

A

Chorionic villus sampling after 10 weeks. (1 in 100 risk of miscarriage)
Amniocentesis after 15 weeks (1 in 200 risk of miscarriage)
Umbilical cord sampling after 16 weeks.

43
Q

What 3 diseases are screened for in a newborn that are federally mandated?

A

Congenital hypothyroidism
Galactosemia
Phenylketonuria

44
Q

What is the genetic information nondiscrimination act?

A

Prohibits health insurers from using genetic info to determine eligibility/premiums.
Also prohibits employers from discriminating using genetic info

45
Q

What is a Barr body?

A

An inactivated X chromosome.

AKA females have 1, males have 0.

46
Q

What is the SRY gene?

A

Gene found in the Y chromosome, initiates male sex development and anti-mullerian hormone production, which suppresses female gonads.

47
Q

What can heavy doses of ionizing radiation cause?

A

Microcephaly, skeletal malformation, mental retardation

48
Q

What is the purpose of a nuchal translucency test? When is it done?

A

11-13 weeks, results are combined with PAAP-A and hCG to check for trisomy risk.

49
Q

What is the prupose of a cell-free DNA test? When is it done?

A

10-13 weeks, part of screening for trisomy.

50
Q

What is the purpose of a quad-screen?

A

AFP, hCG, inhibin A, unconjugated estradiol
Screening for neural tube defects and down syndrome.

51
Q

What is the purpose of a chorionic villus sampling?

A

DNA and chromosomal abnormality check.

52
Q

What is the purpose of an amniocentesis?

A

Early, it is used to confirm an abnormal quad screen/US/carrier testing.

If done later, it is to check fetal lung development or infection.

53
Q

What is the purpose of umbilical cord sampling?

A

Prenatal screening for disorders/infection.

(D) MOD (16 decks)

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