Chromosome number

Question 1

Karyotype Nomenclature

Answer 1

number of chromosomes, sex chromosomes, numerical aberrations, structural aberrations

46,XY: normal male
47,XX,+21: female with Down syndrome
46,XY,del(4)(p14): male with deletion from short arm of chromosome 4 from band p14

Question 2

Aneuploidy

Answer 2

one homologous pair affected (trisomy)

caused by nondisjunction, deletion of centromere, robertsonian translocation (philadelphia chromosome)

Question 3

Polyploidy

Answer 3

all chromosome pairs have an extra

caused by dispermy or meiotic failure

Question 4

Down syndrome (21)

Answer 4

intellectural, flat facies, prominent epicanthal folds, single palmar crease

familial DS: long arm of chromosome 21 attached to 15, carriers phenotypically unaffected bc no loss of genes

Question 5

Edward’s sundrome (18)

Answer 5

prominent occiput, rocker bottom feet, intellectual disability, nondisjunction, overlapping fingers

Question 6

Patau syndrome (13)

Answer 6

intellectual disability, rocker ottom feet, microcephaly, cleft palate, cutis aplasia

Question 7

Turner syndrome (XO)

Answer 7

loss of X chromosome bc nondisjunction

short, ovarian dysgenesis, shield chest

Question 8

Klinefelter syndrome

Answer 8

multiple X chromosomes and a Y

testicular atrophy, tall, long extremities, female hair distribution

Question 9

trisomy X

Answer 9

tall, learning difficulties, decreased muscle

body inactivates extra x chromosomes but not perfectly

Question 10

Jacobs syndrome

Answer 10

extra Y chromosome

tall, fertile, severe acne, learning disability, ASDs