Chromosomal Abberations and Open Questions (GEN)

Question 1

Down syndrome

Answer 1

Trisomy 21

47 (XX/XY) t21

Question 2

Edwards syndrome

Answer 2

Trisomy 18

47 (XX/XY) t18

Question 3

Patau syndrome

Answer 3

Trisomy 13

47 (XX/XY) t13

Question 4

Angelman syndrome

Answer 4

Maternal deletion of 15q 11-13

46 (XX/XY) 15q 11-13

Question 5

Prader-Willi syndrome

Answer 5

Paternal deletion of 15q 11-13

46 (XX/XY) 15q 11-13

Question 6

Turner syndrome

Answer 6

Monosomy X

45 XO

Question 7

Klinefelter syndrome

Answer 7

47 XXY

Question 8

Huntington disease

Answer 8

AD
Chromosome 4 CAG repeated in HTT gene > 36 times
Higher number of repeats -> earlier symptoms (anticipation)

Question 9

Myotonic dystrophy

Answer 9

AD
Type 1 -> 19q CTG repeated in DMPK gene
Type 2 -> 3q CCTG repeated in CNBP gene

Question 10

Fragile X syndrome

Answer 10

X-linked dominant

CGG repeated in FMR1 gene

Question 11

Friedrichs Ataxia

Answer 11

AR

Chromosome 9 GAA repeat in FXN gene

Question 12

Cri du Chat

Answer 12

Deletion of 5p

46 (XX/XY) 5p-

Question 13

Williams syndrome

Answer 13

Microdeletion of 7q 11.23

46 (XX/XY) 7q 11.23

Question 14

DiGeorge syndrome

Answer 14

10% AD
22q 11.2 deletion (catch 22)
46 (XX/XY) 22q 11.2

Question 15

Burkitt lymphoma

Answer 15

t(8;14) (q24;q32)

dysregulation of c-myc

Question 16

Classify the complex inherited traits and diseases, give examples for each group!

Answer 16

Complex traits: results of multiple genetic and enviromental factors, does not behave according to mendelian laws.

Congenital malformations: cleft lip, cleft palate, neural tube defects, congenital heart diseases
Chronic adult diseases: obesity, diabetes, hypertension, autoimmune

Question 17

Describe the process of X inactivation. Why, when, in whom, and how does it happen. How many X is inactivated? What is the consequence of it?

Answer 17

One copy of X chromosome is inactivated in female mammals.
Silenced and packed into heterochromatin.
Prevents females from having twice as many gene copies as males.
One X will be inactivated.
Visible as Barr body, periphery of nucleus.

Question 18

Define proteomics:

Answer 18

Proteomics: large scale study of proteins. (Proteome: entire set of proteins in an organism/system)

Question 19

What can be the genetic causes of Prader-Willi syndrome? Describe these genetic causes.

Answer 19

Paternal deletion of 15q 11-13
- deletion of Prader-Willi gene on chromosome 15

Maternal uniparental disomy
- both copies of cr. 15 from mother, both epigenetically methylated and silenced: with no paternal cr. 15 - no expression of PW gene

Wrong imprinting
- Mutation in imprinting center causes paternal PW to be silenced

Question 20

Define genome:

Answer 20

All nuclear and mitochondrial DNA

Question 21

Define pleiotropy:

Answer 21

The control of more than one trait by a single allele

- one gene influences two or more seemingly unrelated traits

Question 22

Define mosaicism and give cause

Answer 22

Mosaicism: the presence of two or more populations of cells with different genotypes from a single zygote
Cause: nondisjunction

Question 23

Define chimerism

Answer 23

Chimerism: presence of two or more cell lines of different origins (different zygote)
Cause: fusion of fraternal twins, double fertilization of egg, polar bodies

Question 24

Define functional mosaicism

Answer 24

Functional mosaicism: identical cells use different proteins to carry out the same function

Question 25

Define histone modification and list the different types; what is their significance?

Answer 25

Histone modification: Epigenetic processes 1. Acetylation 2. Methylation 3. Phosphorylation 4. Ubiquination 5. SUMOylation Activates/silences genes without altering nucleotide sequence

Question 26

Describe the meaning of the followings: Sex linked, sex limited and sex influenced inheritance. (Do not forget to give the location of gene responsible for the trait in these different inheritances). Give one example for each.

Answer 26

Sex linked - gene is located on chromosome on sex chromosome (X or Y) -> Duchenne m. Dystrophy, dystrophin, short arm of chr. X, deletion Sex limited - gene present in both sexes, but are expressed only in one sex - > on autosomes - > Prostate cancer/ovarian cancer Sex influenced - same gene shows different expression in each sex - > on autosomes - > body/facial hair - > presence/absence of hormones - > male pattern baldness