Numerical Chromosomal Aberrations

Question 1

Trisomy 21

Answer 1

(47, XX/Y, +21)

Rare 1:600-800
Symptoms: newborns have hypotonia decreased muscle tone +mental retardation

Life expectancy limited bc suffer from
- Heart + Internal organ defects
- Immune system defects (result in cancer)
- Alzheimer’s disease (AD) due to most common ad gene on 21 chromosome therefore 3 copies increases changes of AD

Physical ways to diagnose:
- Macroglossia
- Flat occiput (shape of head), flat face and dysmorphic ears
- Unslanting palpebral fissures
- Epicantheal fold (prominent?)
- Palmar crease and short fingers

Question 2

Numerical chromosomal aberrations types

Answer 2

2 types:

1) Aneuploidy: changes in chromosome number of 1 or more

• Monosomy one less chromosome: total 45
• Trisomy one extra copy: total 47

2) Polyploidy: changes in chromosome number of multiples

• Triploidy 3n: total 69 chromosomes
• Tetraploidy 4n: total 92 chromosomes

Question 3

List of basic structural syndromes

Answer 3

Numerical abnormalities of Autosomes:

• Down syndrome (47, XX/Y, +21)
• Patau syndrome ((47, XX/Y, +13)
• Edwards syndrome (47, XX/Y, +18)

Of sex chromosomes:

• Turner syndrome (45, X)
• Klinefelter syndrome (47, XXY)
• XYY syndrome (47)
• triple X syndrome (47,XXX)

Question 4

Patau’s syndrome

Answer 4

(47, XX/Y, +13)
Rare 1: 15,000-20,000

Symptoms:
Severe retardation

congenital heart defects  

Urogenital defects  

CNS malformation 

Mostly die in first month  

physical ways to diagnose:

Microphthalmia one/both eye too small rarely cyclopia fusion of both eyes

Microcephaly small head

Malformed low set ears, cleft lip+palate

Polydactyly extra digits

Question 5

Edwards syndrome

Answer 5

(47, XX/Y, +18)

Rare: 1- 5,000-10,000
Symptoms:
Severe developmental retardation
Failure to thrive
Heart + Kidney defects

physical ways to diagnose:
Mycrocephaly
Micrognathia- lower jaw undersized
Digits overlapping, hypoplastic nails underdeveloped
Prominent occiput w malformed low set ears

Question 6

Turner syndrome

Answer 6

(45,XO)
Rare: 1: 2,000-2,500

Symptoms

• Short stature
• Gonadal dysgenesis
• Primary amenorrhea menstruation by 15
• Sterility infertile
• Average intelligence

physical ways to diagnose:
1) Webbed neck= pterlygium colli congenital skin fold

2) Hygroma colli cysticum (cystic hygroma colli)- related to lymphatic system

3) Fetal hydrops- generalized edema (swelling caused by fluid)

4) Palms+ feet oedemas in newborn

5) Shield chest

6) Underdeveloped breast widely spaced nipples

7) Hypertelorism wide space between eyes

Question 7

Klineffelter syndrome

Answer 7

47, XXY)
Rare: 1: 500-1,000
Symptoms:
- Hypoplastic testes
- Cryptorchism undescended testis
- Sterility- azoospermia no sperm
- Avg intelligence
- Tall stature

physical ways to diagnose:

1) Hyalinized seminiferous tubules

2) Female fat distribution, gynecomastia breast fat

3) Female hair pattern, poor beard growth

Question 8

triple X syndrome

Answer 8

(XXX)
Rare: 1:1000

Avg intelligence+ normal development

Decreased fertility (surprise abortions), w out risk of chromosomal aberrations in offspring

No increased incidents of congenital anomalies

Question 9

XYY syndrome

Answer 9

Robust growth (proportional), avg intelligence normal sexual develop

Normal fertility w out risk of chromosomal aberrations in offspring