Chromosomal Abnormalities & Investigations

Question 1

What happens to centromere with age?

Answer 1

It becomes smaller

Question 2

What are chromosomes like in interphase?

Answer 2

Longest and thinnest

Question 3

What are chromosomes like in prophase?

Answer 3

Increase in thickness but decrease in length

Question 4

What are chromosomes like in anaphase?

Answer 4

The smallest

Question 4

What are chromosomes like in metaphase?

Answer 4

Very thick, quite short and well spread in the cell

Question 5

At which stage are chromosomes most easily observed?

Answer 5

Metaphase

Question 6

What are chromosomes composed of?

Answer 6

DNA, RNA and protein

Question 7

What are the three classes of chromosomes?

Answer 7

Metacentric, Submetacentric and Acrocentric

Question 8

What can chromosomal abnormalities cause variation in?

Answer 8

Number and structure

Question 9

What is aneuploidy?

Answer 9

Variation in the number of chromosome within a set.
Hyperploidy
Hypoploidy
Polyploidy

Question 10

What are structural changes of chromosomes?

Answer 10

Genetic information can be changed (more or less) or rearranged

Question 11

What are the two types of mutations?

Answer 11

Chromosome mutation and gene mutation

Question 12

Examples of chromosome mutation?

Answer 12

Deletion
Duplication
Inversion
Translocation

Question 13

Examples of gene mutation?

Answer 13

Point mutation: silent, missense, nonsense.
Frame shift: deletion, addition

Question 14

What are the types of transaction?

Answer 14

Reciprocal and Robertsonian

Question 15

What is reciprocal translation?

Answer 15

Segments from two different chromosomes are exchanged

Question 16

What is Robertsonian translocation?

Answer 16

Entire chromosome attaches to another

Question 17

How are genetic abnormalities detected?

Answer 17

Screening tests
Diagnostic tests

Question 18

Examples of screening tests?

Answer 18

Ultrasound
Maternal Serum Screening

Question 19

When is ultrasound performed?

Answer 19

10 to 14 weeks

Question 20

What are some signs that could portray Down syndrome through ultrasound?

Answer 20

Thickening of skin over the back of the fetal neck “nuchal translucency”

Question 21

When is maternal serum screening done?

Answer 21

14 to 20 weeks

Question 22

What does MSS screen for?

Answer 22

Down syndrome and spina bifida

Question 23

What does MSS measure?

Answer 23

HcG (high levels indicate DS)
α-fetoprotein (low levels indicate DS)
unconjugated estriol (low levels indicate DS)

Question 24

Examples of diagnostic testing?

Answer 24

Amniocentesis Chorionic Villus Sampling

Question 25

When is CVS performed?

Answer 25

10 to 13 weeks

Question 26

When is amniocentesis performed?

Answer 26

16 to 18 weeks

Question 27

What is karyotyping?

Answer 27

Study that determines the number and structure of chromosomes and also detects common abnormalities

Question 28

What allows for karyotyping?

Answer 28

Parents: - Mother > 35 years old - 3 or more miscarriages - Stillbirths with suspected chromosomal abnormality - Infertility Family history of: - chromosome rearrangement intellectual disability Patients with: - Characteristics of chromosomal syndromes - Delayed puberty - Congenital abnormalities - Ambiguous genitalia

Question 29

Where is the sample for karyotyping collected from?

Answer 29

Peripheral blood Amniotic fluid Skin fibroblast Bone marrow cells

Question 30

What is the process of karyotyping?

Answer 30

- Collect cell from individual - Induce the cell to divide - Stop cell division in metaphase using colchicine - Stain chromosomes to make them visible using Giemsa stain

Question 31

Which chromosomes are in Group A?

Answer 31

1 to 3, they are the largest and centromere is in the middle

Question 32

Which group are chromosomes 6 to 12 and X in?

Answer 32

Group C, mid-size, centromeres located either middle or subterminally

Question 33

Which chromosomes are in Group B?

Answer 33

4 and 5, large and centromere is at subterminal region.

Question 34

Which group are chromosomes 13 to 15 in?

Answer 34

Group D, mid-size, centromeres located terminally

Question 35

What is Group E?

Answer 35

Chromosomes 16 to 18, slightly smaller than D. 16 has centromere in middle, 17 and 18 at more distal regions

Question 36

Which chromosomes are in Group G?

Answer 36

21, 22 and Y, Y is longer than 21 and 22

Question 37

What is Group F?

Answer 37

19 to 20, short chromosomes, centromere in the middle

Question 38

What are the different kinds of Down syndrome?

Answer 38

Trisomy 21, Translocation trisomy 21, Mosaic Trisomy 21

Question 39

What are some clinical features of DS?

Answer 39

Upslanting eyes Epicanthic folds Flat nasal bridge Low-set small ears, Short neck, Abnormal teeth Short broad hands, Transverse palmar crease Space between the first and second toea

Question 40

What are some other issues that come along DS?

Answer 40

Intellectual disability Dementia Heart Disease GI Abnormalities Obesity Eye Problems Hearing Loss Endocrine Disorders Haematological Disorders

Question 41

What is Turner Syndrome?

Answer 41

45 XO

Question 42

Main features of Turner Syndrome?

Answer 42

Puffy hands and feet Webbing of neck Short stature Low hairline at the back of the neck Broad chest, widely spaced nipples Poorly formed or absent ovaries Infertility Learning disabilities

Question 43

What is 47, XXY?

Answer 43

Klinefelter syndrome

Question 44

Main features of Klinefelter syndrome?

Answer 44

Lower IQ Tall stature Poor muscle tone Reduced secondary sex characteristics Gynaecomastia Small testes/infertility Sparse body hair

Question 45

What happens if there is triploidy, 69 chromosomes?

Answer 45

Lethal condition

Question 46

What is Cri-du-Chat?

Answer 46

46, XX, del(5)

Question 47

Main features of Cri-du-Chat?

Answer 47

High-pitched cry, Widely set eyes Low-set ears, Small jaw, Downward slanting fissures Microcephaly, Intellectual disability

Question 48

What is Edward's?

Answer 48

Trisomy 18

Question 49

What is Patau's?

Answer 49

Trisomy 13

Question 50

What is a chromosomal abnormality caused by duplication?

Answer 50

Pallister Killian

Question 51

What causes acute myelogenous syndrome?

Answer 51

Translocation, part of 22 moves to 9