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LMP301 > LMP301 Lecture 18: Prenatal Screening & Neural Tube Defects > Flashcards

LMP301 Lecture 18: Prenatal Screening & Neural Tube Defects Flashcards

1
Q

define: genetics

A

the science of inheritance

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2
Q

define: Mendelian genetics

A

single gene (disorders)

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3
Q

define: genomics

A

science of the genome

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4
Q

define: genome

A

genetic information specifying an organsim

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5
Q

define: gene

A

a genetic unit

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6
Q

define: single-copy, translated gene

A

gene making a protein

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7
Q

define: locus

A

a genetic location

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8
Q

define: allele

A

a genetic variant at a locus (wild type vs. mutant)

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9
Q

define: diallelic

A

2 alleles at a locus

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10
Q

define: chromosome

A

assembly of genes packed together

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11
Q

define: euploidy

A

normal number of chromosomes (23 pairs in humans)

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12
Q

define: aneuploidy

A
  • abnormal number of chromosomes

- abnormal content in chromosomes

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13
Q

trisomy 21

A

genome with 3 copies of chr 21 (Down Syndrome)

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14
Q

how many genomes can 1 person have?

A

2 (1 from mom and 1 from dad)

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15
Q

besides the 46 chromosomes, what other genomes do we have?

A
  • 100 - 1000 mitochondrial genomes
  • organ transplant receivers have 4
  • bacterial genomes (millions)
  • viral genomes (billions, even more if have flu)
  • harmless parasitic genomes
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16
Q

50% of a buccal swab DNA is…

A

bacterial

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17
Q

where are most parasites in our body found?

A

GI

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18
Q

How many genomes do transplanted hearts have?

A

4

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19
Q

define: gene pair

A

joining of 2 haploids (sperm & egg)

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20
Q

what forms about 4 days after fertilization?

A

morula

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21
Q

what is the morula?

A

a solid ball of cells resulting from division of a fertilized ovum, and from which a blastula is formed.

cells begin differentiating process to become embryonic sac, embryo…etc.

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22
Q

size of embryo at 12-15 weeks

A

dime

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23
Q

when is fetal death the highest?

A

very early pregnancy; levels off at 20 weeks

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24
Q

why is there substantial rate of embryo loss in very early pregnancy?

A
  • minimizes the possibility of severe malformations
  • correct for serious mutations & maldevelopment
  • shutdown developmental process early
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25
Q

how is the embryo lost early pregnancy?

A
  • miscarriage

- menstrual loss

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26
Q

the neural tube forms the…

A

CNS

  • brain
  • spinal cord
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27
Q

the neural tube forms from the…

A

ectoderm

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28
Q

what is the incomplete neural tube referred to?

A

neural groove

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29
Q

what surrounds the neural tube during development?

A

somite

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30
Q

NTD

A

neural tube defects

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31
Q

NTD is a family of…

A

complex congenital malformations

32
Q

NTD is caused by…

A

failure of neural tube closure at week 3-4

33
Q

what does spina bifida lead to?

A

early death (stillborn) / life-long paralysis

34
Q

mild form of spina bifida is called…

A

spina bifida occulta; does not affect nervous system (problems with vertebrate)

35
Q

how can spina bifida occulta be detected?

A

x-ray (see defect in lower spine)

36
Q

anencephaly

A

neural tube didn’t close at rostral region (near head)

37
Q

which part of the neural tube may lead to spina bifida?

A

failure to close at lower spine area

38
Q

consequences of anencephaly

A

lethal

  • miscarriage
  • early stillbirth
  • brief livebirth
39
Q

examples of NTD

A
  • spina bifida (occulta)

- anencephaly

40
Q

NTD is a ____ disorder

A

complex

41
Q

complex disorder

A
  • not due to single gene defect (multiple genes, environment, other factors…)
  • complex inheritance patterns
42
Q

some examples of complex disorders with genetic components

A
  • cancer
  • heart disease
  • diabetes
  • NTD
43
Q

exposed neural tissue produces…

A

alpha-fetoprotein

44
Q

what can increase a-fetoprotein production?

A

when the neural tissue nerves are exposed to amniotic fluid (more and more a-fetoprotein produced as the embryo develops)

45
Q

a-fetoprotein can be foun din…

A

amniotic fluid

  • production begins at week 10
  • amount peaks at week 12-13
  • no AFP found after week 31
46
Q

amniocentesis

A

poking syringe in stomach, and drawing out some amniotic fluid for testing

47
Q

how can NTD be tested for (invasive)

A

look for AFP by doing amniocentesis

48
Q

how can NTD be tested for (non-invasive)

A

AFP crosses to maternal serum via placenta -> maternal serum screen

49
Q

why is maternal serum screen not the best test to use?

A
  • only get a % risk
  • many overlaps and false results
  • cannot distinguish between types of NTD
50
Q

Prenatal screening couples…

A

NTD screening with screening for trisomy 21

51
Q

is prenatal screening required?

A

no, the parent can decide

52
Q

if screening detects there is something wrong, what is done next?

A

ultrasound

53
Q

can we decide what is wrong based on screenings?

A

no, it is not a diagnosis; further testing must be done

54
Q

what is used as a diagnosis for NTD?

A

outpouching (around lower spine/butt), seen from ultrasound

55
Q

what non-genetic factors affect NTD?

A

Nutrition & diet

- famine during WWII caused dramatic increase of NTD

56
Q

what nutrient is used to decrease instances of NTD?

A

folic acid

57
Q

what effect does folic acid have on NTD?

A
  • decrease reccurence (if previous baby had NTD)
  • prevent (if first baby)

HAS NOT ELIMINATED!

58
Q

serum folate is transported into the cell by…

A

hFR & RFC transporter

59
Q

the folate found inside the cell is called…

A

5-methyl THF

60
Q

folate cycling drives…

A

DNA methylation

61
Q

5-methyl THF is converted to ___ by ___

A

methionine

methionine synthase

62
Q

describe folate cycling (slide 21)

A

1) 5-methyl THF -> methionine -> SAM
2) SAM adds methyl group on DNA
3) SAM -> SAH -> homocysteine
4) homocysteine -> cystathionine -> cysteine

63
Q

homocystein is converted by cystathionine by ____

A

CBS

64
Q

folate supplements is recommended for…

A

all women of reproductive age

65
Q

rates of folate supplement use from 1992 to 2001

A

slowly increasing, but still less than 50% (bad!)

66
Q

how is folate supplemented in Canadian diet?

A

fortified into cereal grains (white flour)

67
Q

how much additional folate would be provided through fortification of grains?

A

0.2 mg/day

68
Q

ARIMA

A

auto-regressive integrated moving average

69
Q

Regions in Canada that had the biggest difference after folate fortification (decrease in NTD)

A

atlantic region (PE, NS, NL)

70
Q

folate needs another vit to work properly. what is this vit?

A

vit B12

71
Q

why is vit B12 needed for folate to work properly?

A

B12 is used in folate cycling

72
Q

which enzymes are used in folate cycling?

A
  • MS
  • MTHFR
  • MTRR
73
Q

Folate is a __ factor

A

growth

74
Q

too much folate may be associated with…

A
  • more rapid growth of colorectal cancers
  • shortened survival of cancer patients
    (only affect those who already have cancer/predisposition for cancer)
75
Q

folate may cause cancer?

A
  • decrease chances if you don’t have cancer

- increase cancer aggressiveness if you already have cancer

LMP301 (18 decks)

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