Chromosomal abnormalities

Question 1

How do you analyse chromosomes?

Answer 1

Using a metaphase spread= fix chromosomes on slide & stain them
Karyotype picture produced and can identify chromosome banding

Question 2

What should each chromosome contain?

Answer 2

P arm, Q arm and centromere

Question 3

How do scientists identify chromosomes?

Answer 3

1- Size
2- Banding pattern
3- Centromere position

Question 4

What are acrocentric chromosomes?

Answer 4

Centromere is located very near the top of the chromosome so only the q arm (very little/ no p arm)

Question 5

What is a normal female karyotype?

Answer 5

22 pairs XX

Question 6

What is a normal male karyotype?

Answer 6

22 pairs XY

Question 7

What abnormalities can be picked up on a karyotype?

Answer 7

• Abnormal chromosome number
• Abnormal chromosome material location
• Abnormal amounts of chromosome material (bits missing or extra)

Question 8

What are the 3 main types of chromosomal abnormalities?

Answer 8

Aneuploidies
Microdeletions
Translocations

Question 9

What is aneuploidy?

Answer 9

Abnormal number of copies of an individual chromosome

Question 10

What is Monosomy?

Answer 10

1 chromosome missing, Total= 45

Question 11

What is Trisomy?

Answer 11

1 chromosome extra, Total= 47

Question 12

What is polyploidy?

Answer 12

Abnormal number of sets of chromosomes

Question 13

What is Monoploid?

Answer 13

One set, Total= 23 pairs

Question 14

What is Diploid?

Answer 14

Two sets, Total= 46 pairs

Question 15

What is Triploid?

Answer 15

Three sets, Total= 69 pairs

Question 16

What are deletions?

Answer 16

Loss of a segment of genetic material from a chromosome

Question 17

What are duplications?

Answer 17

Gain of a segment of genetic material from a chromosome

Question 18

What are microdeletions/ microduplications?

Answer 18

too small to be seen on a karyotype

Question 19

What is the consequence of deletions & duplications?

Answer 19

depends on which genes are in the deleted/ duplicated region

Question 20

What is a translocation?

Answer 20

Relocation of chromosome material to the wrong place

Question 21

What is a reciprocal translocation?

Answer 21

2 different chromosomes have exchanged segments with each other

Question 22

What is a Robertsonian translocation?

Answer 22

An entire acrocentric chromosome attaches to another at the centromere

Question 23

What is a balanced translocation?

Answer 23

All chromosome material present (just in the wrong place)

Question 24

What is an unbalanced translocation?

Answer 24

Relocation has resulted in loss and/ or gain of chromosome material

Question 25

What is down syndrome?

Answer 25

Trisomy 21 (3 copies of chromosome 21)

Question 26

What are the 6 clinical features of Down’s syndrome?

Answer 26

• Characteristic facial features
• Mild= moderate intellectual disability
• Short stature
• Congenital heart disease
• Endocrine problems
• Increased risk of leukaemia and Alzheimer’s

Question 27

What is Edward’s Syndrome?

Answer 27

trisomy 18

Question 28

What are the 6 clinical features of Edward’s syndrome?

Answer 28

• Intra-uterine growth restriction
• Most die during pregnancy/ neonatal period
• Overlapping fingers
• Rocker-bottom feet
• Congenital heart/kidney disease
• Small head size (microcephaly)

Question 29

What is Patau’s syndrome?

Answer 29

Trisomy 13

Question 30

What are 6 clinical features of Patau’s syndrome?

Answer 30

• Intra-uterine growth restriction
• Most die during pregnancy/ neonatal period
• Cleft lip/ palate
• Extra fingers/ toes
• Brain abnormalities
• Congenital heart disease

Question 31

What is Antenatal combined screening?

Answer 31

Combined scan for down’s syndrome, edwards syndrome and pataus syndrome, done via blood test & ultrasound scan

Question 32

What is Klinefelter syndrome?

Answer 32

47 XXY

Question 33

What are 4 clinical features of Klinefelters syndrome?

Answer 33

• Tall stature
• Normal intellect
• Infertile- often diagnosed in a fertility clinic
• Little facial/ body hair

Question 34

What is Turner syndrome?

Answer 34

Monosomy X (45, XO)