Exam #3: Genetic Disorders III Flashcards Preview

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Flashcards in Exam #3: Genetic Disorders III Deck (41):
1

What are the trinucleotide repeat disorders?

Abnormal copies of a tri-nucleotide repeat

2

What is the repeat seen in Fragile X Sydrome? How many repeats are needed for symptoms?

CGG
> 230

****Seen in the UTR just after the promoter

3

What is the repeat seen in Huntington Disease? How many repeats are needed for symptoms?

CAG
>36

*****In the exon

4

What is genetic anticipation?

Worsening of the disease & earlier expression of the disease as it is passed down from generation b/c of amplification of the trinucleotide repeats

5

What is the inheritance pattern for Huntington Disease?

Autosomal Dominant

6

What is the inheritance pattern for Fragile X- Syndrome?

X-linked Dominant

****With a reduced penetrance

7

What is Fragile X Syndrome?

This is the leading cause of INHERITED mental impairment & the leading known cause of autism/autism spectrum disorder

8

Which sex is Fragile X Syndrome worse in?

Males

9

What is the difference between Down's Syndrome & Fragile X?

Down's Syndrome is NOT inherited i.e. why Fragile X Syndrome is the most common INHERITED cause of mental impairment

10

How is Fragile X-Syndrome diagnosed?

Southern Blot

11

Describe how Fragile X-Syndrome is associated with the number of repeats?

****Increased repeats= increased severity of symptoms*****

12

What are the symptoms of Fragile X-Syndrome in males?

Mental impairment w/
1) Big ears
2) Big upper jaw
3) Big testicles (macroorchidism)

13

What are the symptoms of Fragile X-Syndrome in females?

Milder symptoms including mental impairment
- Fewer physical findings

14

What is Huntington's Disease?

This is a severe neurodegenerative disorder caused by a TRE that is inherited in an autosomal dominant fashion

15

What is the mean age of onset for Huntington's Disease?

35-44 years

16

Describe the progression of symptoms in Huntington's Disease.

Early
Intermediate
Late

17

What region of the CNS is affected by Huntington's Disease?

Caudate nucleus has neuronal dropout/ atrophy leading to gliosis

18

What number of trinucelotide repeats is associated with Juvenile Huntington's Disease?

>60

19

What is a Robertsonian Translocation?

Unequal translocation where large arms come together

20

What is Edward's Syndrome?

Trisomy 18 due to chromosomal nondisjuction during meiosis

21

What is the presentation of Edward's Syndrome?

Low survival rate due to:
1) Heart abnormalities
- VSD
2) Kidney malformations
- Horseshoe kidney
3) Internal organ disorders
4) Prominent occiput
5) Rocker bottom feet
6) Small jaw

Severe mental retardation

22

What is Patau Syndrome?

Trisomy 13 due to a Robertsonian translocation--most die within the first year of life

23

Describe the presentation of Patau Syndrome.

Generally, there are midline developmental defects including:

1) Microcephaly & mental retardation
2) Microphthalmia
3) Polydactyly
4) Clef lip & palate
5) Cardiac Defects
6) Renal defects
7) Rocker-bottom feet

24

Outline the incidence of the trisomies.

Down's
Edward
Patau

25

What is Turner's Syndrome?

45, X
- Female

****The problem is the male sperm that is lacking an X chromosome

26

What is Klinefelter's Syndrome?

47, XXY

27

What are the prenatal & post-natal features of Turner's Syndrome?

- Common cause of miscarriage
- Cystic hygroma
- Webbed neck
- Puffy hands
- Puffy feet

28

What are the cardiac anomalies that are seen with Turner's Syndrome?

- Bicuspid aortic valve
- Coarctation of the aorta

29

What is a cystic hygroma?

Not a neoplasm; rather, a failure of lymphatics to drain properly-->leads to the webbed neck

30

What are the features of Turner's Syndrome that are typically manifested at puberty?

- Short stature
- Absence of ovaries

31

What is a streaked ovary?

Stroma of the ovary without follicles

32

What are the features of Turner's Syndrome that are typically manifested at puberty?

- Short stature
- Absence of ovaries

*****Failure of feminisization in puberty is the typical presentation (common cause of primary amenorrhea)

33

What causes the extra-X chromosome in Klinefelters Syndrome?

Mother or father passes on an extra X chromosome

34

Describe the phenotype of Klinefelter's Syndrome.

- Taller stature
- Feminized physique

35

What is the risk of breast cancer in Klinerfelters Syndrome?

20% increased b/c

- Gynecomastia
- Hyperestrogenism

36

When is Klinefelter's Syndrome typically diagnosed?

Puberty

37

What is Prader WIll- Angleman Syndrome?

Generally, these are two congenital disorders caused by errors in genetic imprinting

38

What is genetic imprinting?

Turning off a gene with methylation

39

Which Syndrome, Prader-Willi or Angelman is associated with the mother? Father?

Methylated & shut off

Maternal= Angleman
Paternal= Prader Willi

40

What are the symptoms of Prader Willi Syndrome?

- Truncal obesity
- Hypogonadium
- Small hands
- "Dull"
- Outbursts of extreme violence

41

What are the symptoms of Angleman Syndrome?

- Wide stance
- Arm position
- Spasticity
- "Happy puppets"