Chromosomal Abnormalities, Block 3

Front 1

Presentation:
Pseudohypertrophy of the calves;
Progressive muscle weakness
Genetic disorder displaying Mosaicism

Back 1

Duchenne Muscular Dystrophy
X-linked recessive disorders
Dystrophin protein bound to muscle membrane helps maintain integrity of muscle fiber;
Anchors parts of internal cytoplasm to surface membrane

Front 2

Can Tortoiseshell cat be a male?

Back 2

Yes, XXY

Front 3

Non-disjunction in Meiosis I

Back 3

No normal gametes; 2 trisomy and two monosomy gametes

Front 4

Non-disjunction in Meiosis II

Back 4

two normal gametes, one monosomy and one trisomy

Front 5

Down syndrome is a consequence of?

Back 5

Trisomy 21; Robertsonian (94%) translocation (3.3%) and Mosaicism (2.4%)

Front 6

What is the heart defect found in down syndrome patients. How frequently is congenital heart disease encountered?

Back 6

Endocardial cushion defect = atrial and ventrical septal defect.

Front 7

Presentation: occipitant skull; low set malformed ears, hirsute forehead, clenched hands, and short sternum...

Back 7

Trisomy 18

Front 8

What heart defects are seen in Trisomy 18?

Back 8

VSD, ASD, PDA

Front 9

What is life expectancy for trisomy 18?

Back 9

90% die in the first year

Front 10

Trisomy 13: describe

Back 10

Trisomy (80%); Robertsonian translocation (15%) and Mosaicism (5%);

Cardiac abnormalities
Polydactaly
Malformed, low set ears; cleft lip and palate

Front 11

Presentation:
polydactaly, sloping forehead, malformed ears, cleft lip, and deep set eyes

Back 11

Trisomy 13

Front 12

Presentation:
Tall, long limbs and small gentialia
Reduced IQ and behavior problems

Back 12

Kleinfelders, XXY

Front 13

Kleinfelders occurs in Meiosis I or II of which parent

Back 13

50% defect in parental Meiosis I
50% defect in parental Meiosis I or II

Front 14

Turner Syndrome

Back 14

45X; meiotic nondisjunction or Mosaicism

Webbed neck, lymphedema, short stature, failure to menarche,

Front 15

Presentation:
Coarctation of the aorta, short stature and webbed neck

Back 15

Turners

Front 16

What does Meiotic nondisjunction lead to?

Back 16

Mosaicism

Front 17

Defective part of chromosome on people with Down's Syndrome

Back 17

21q22.1

Front 18

What are translocations?

Back 18

Rearrangement of parts between NON-HOMOLOGOUS Chromosomes.

Front 19

What is a balanced or unbalanced translocation?

Back 19

Balanced: even exchange of materials with no extra genetic info.

Unbalanced: unequal exchange of chromosomal material (Deletions or duplications)

Front 20

Adjacent I Segregation

Back 20

1 normal, 1 translocated
Gametes have duplications and deletions
Homologues go to opposite anaphase poles
DONT SURVIVE

Front 21

Adjacent II Segregation

Back 21

Gamest have 1 normal and 1 translocated
Homologues to same Anaphase Pole
Gametes have Duplications and Deletions
DONT SURVIVE

Front 22

Alternative Segregation

Back 22

Euploid gametes
Both translocated and both normal

Front 23

Robinson Translocation

Back 23

- Occurs when long q arm of acrocentric chromosomes fuses at centromere
- loss or partial loss of short (p) arms
- 45 chromosomes

Front 24

Most common chromosomes for translocation

Back 24

13, 14 - most common
15,21,22

Front 25

Are the carriers of Robinson translocations phenotypically normal?

Back 25

yes.

Front 26

Possible outcomes of Robertson translocation

Back 26

Normal
Balanced Carrier
Trisomy a
Trisomy b
Monosomy a
Monosomy b

Front 27

Can Robinson translocation happen de novo?

Back 27

yes!

Front 28

4 causes of deletions:

Back 28

crossover errors during mitosis
chromosomal translocations
crossover within a chromosomal inversion
breaking without rejoining

Front 29

Prognosis for deletions?

Back 29

usually fatal if large
less fatal if small.

Front 30

22q11.2 Deletion syndrome

Back 30

Tetrology of Fallot, asymmetric face, less plasma calcium

Front 31

What is segmental aneuploidy?
What are the mechanisms behind it?

Back 31

Duplication!
a) Unequal crossing over between homologous chromosomes
b) crossing over in the inversion loop during meiosis

Front 32

What is one example of chromosomal duplication?

Back 32

Charcot Marie Tooth Disease
Most common form of peripheral neuropathy

Front 33

What are the two types of inversions?

Back 33

Paracentric and Pericentric

Front 34

Paracentric inversion creates gametes with ____ chromosomes?
Are these viable?

Back 34

Dicentric and acentric chromosomes
These are not viable. So there are no abnormal birth outcomes.

Front 35

Pericentric inversion involves or does not involve the centromere?

Back 35

It involves the centromere

Front 36

Pericentric inversion produces gametes with ___? Are they viable?

Back 36

duplications and deletions; they are viable but abnormal