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Genetics > Exam II > Flashcards

Exam II Flashcards

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1
Q

What three trisomys are compatible w/ life?

A

13, 18, 21

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2
Q

Which is the short arm of a choromosone…p or q?

A

p

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3
Q

Symptoms of Trisomy 18

A

Edwards syndrome

  • small size, small head
  • congenital heart defects
  • overlapping fingers
  • only 5% survive beyond 1 year
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4
Q

Frequency of trisomys

A

+21 (down) 1 in 700
+18 (Edwards) 1-2 in 6000
+13 (Patau) 1-2 in 10,000 (biggest chromosome/lots of genes hard to live with)

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5
Q

Symptoms of Trisomy 21

A 
Flat facial profile
upslanted palpebral fissures
abnormal ears
nuchal skin fold
single palmar crease
clinodactyly
intellectual disability
congenital heart disease
leukemia, thyroid abnormalities
hypotonia (decreased muscle)
hyperflexibility
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6
Q

Symptoms of Trisomy 13

A

Patau syndrome: most rare.

scalp defects, 
small head
cleft lip/palate
multiple fingers
renal abnormalities
only 5% survive 6 months
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7
Q

Klinefelter Syndrome

A
  • tall stature,
  • learning differences
  • small testicles
  • infertility
  • man boobs (gynecomastia)
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8
Q

Turner Syndrome

A
  • lymphedema in infancy
  • heart problems
  • short
  • 45X
  • infertility
  • low hairline, short neck
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9
Q

47XXX

A

1/1000
-speech delay, IQ 10-15 below siblings
-increased risk for infertility
Most offspring are chromosomally normal

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10
Q

47 XYY

A

1/1000

  • lower IQ
  • may be at risk for behavioral problems, impulsivity
  • most offspring are chromosomally normal
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11
Q

When does heterodisomy occur?

A

In M1 block (H comes before I)

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12
Q

When does isodisomy occur?

A

If Meiosis II was blocked

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13
Q

Trisomic Rescue

A

When there are 3 chromosomes and one disappears

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14
Q

What percent of SAB’s have a normal karyotype?

A

60%

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15
Q

What is the most frequent trisomy seen in abortions?

A

Trisomy 16

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16
Q

What percent of X genes escape X inactivation?

A

About 15%

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17
Q

steps involved in x-inactivation

A
  1. counting
  2. choice
    - abnormal X inactivated if it has XIST
    - translocation between X and autosome, normal X inactivated
  3. cis inactivation
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18
Q

Example of microdeletion

A

williams syndrome (deletion on chromosome 7 on elastin gene)

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19
Q

example of insertion

A

chrones disease

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20
Q

example of duplications

A

duplication of PMP22 on chromosome 17; Charcot-Marie-Tooth disease (neuropathy)

21
Q

examples of frameshift mutatioons

A
  1. neurofibromatosis type 1
  2. breast and colon cancer
  3. hemophilia
22
Q

Promotor mutation example

A

dyskeratosis congenita: premature aging and bone marrow disease

23
Q

Classical recessive inheritance

A

ex: PKU. when 2 abnormal copies of gene are necessary to see disease

24
Q

Haploinsufficiency

A

AD. When 1 copy is mild, 2 copies is severe. Also called incomplete dominance. Ex: familial hypercholesterolemia

25
Q

Dominant Negative

A

AD. when the mutant copy interferes with the other normal copy. Example: OI

26
Q

How are SNPs inherited?

A

in sets called haplotypes

27
Q

What percent of human genome varies from person to person

A

12%

28
Q

How was kabuki syndrome discovered?

A

Whole exome sequencing.

29
Q

What percent of cancers are germline?

A

5-10%

30
Q

What are indications of hereditary cancer?

A

young age <50, bilateral tumors, rare tumors

31
Q

What are examples of hereditary cancers?

A

retinablastoma in both eyes, whilms tumor

32
Q

How many gene copies in an oncogene need to be mutated to get cancer?

A

1

33
Q

What are examples of oncogene mutation cancers

A

RET (multiple endocrine neoplasia, BCR (leukemia) and HRAS=costello

34
Q

What are examples of tumor suppressor genes?

A

Rb, NF1, p53, APC

35
Q

What is an example of a mismatch repair cancer?

A

lynch syndrome/HNPCC (need 2 copies mutated)

36
Q

What combinations of cancers in a family history are indicative of hereditary cancer?

A

Breast, pancreatic, ovarian (BRCA)

Breast, sarcomas, leukemia, brain (p53)

37
Q

red flags for BRCA

A

early onset, male breast cancer, ovarian cancer, bilateral, ashkenazi jewish descent (1/40 carrier rate)

38
Q

What things ameliorate BRCA risk?

A
  1. breast feeding >12 months
  2. oral contraceptive use
  3. Masectomy reduced cancer by 95%
  4. Oophorectomy reduced risk by age 40

More children increased risk for BRCA 1 but not 2

39
Q

What is an example for a variable penetrance inherited cancer?

A

Colorectal cancer.

Familial adenomatous polyposis coli

40
Q

Which diagnostic test can be performed 1st semester?

A

CVS; amniocentesis is second semester

41
Q

When can a nuchal translucency test be performed and what is the measurment that indicates risk for aneuploidy?

A

11-13 weeks, >3 mm

42
Q

What percent of aneuploidy does nuchal translucency detect?

A

60%

43
Q

What is an echogenic intracardiac foci?

A

a soft marker that has an increased risk of T21 seen on an ultrasound

44
Q

What gets tested in a maternal serum marker?

A

11-13 weeks: free B-HcG, PAPPA

2nd tri: quad screen, AFP, uE3, HcG, inhibin A

45
Q

When is NIPT not useful?

A

not valid in twins, not enough data

46
Q

When is CVS used?

A

10-13 weeks. 1-300 chance of miscarriage

1% chance of confined mosaicism

47
Q

What is pre implantation genetic screening?

A

use a microarray to test for aneuploidy; not diagnostic due to mosaicism

48
Q

What is a pre implantation genetic diagnosis?

A

looks for 1 family gene mutation; not actually diagnostic

Genetics (2 decks)

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