Chromosomal Abnormalities

Question 1

What is cytogenetics?

Answer 1

The study of the structure and function of chromosomes

Question 2

What is cytogenetics used for?

Answer 2

Used for the screening and diagnosis of inherited chromosomal disorders

Question 3

What is a karyotype?

Answer 3

A preparation of chromosomes arranged in size order eg. male human karyotype 2n=46

Question 4

What are the three ways to identify a chromosome?

Answer 4

Length
Banding pattern
Placement of centromere

Question 5

What is metacentric?

Answer 5

Centromere in the centre

Question 6

What is sub-metacentric?

Answer 6

Centromere off centre

Question 7

What is acrocentric?

Answer 7

Centromere very close to the end

Question 8

What is karyotyping used for?

Answer 8

To detect changes in chromosome number

To detect changes in chromosome structure

Question 9

What is polyploidy?

Answer 9

Extra whole sets of chromosomes

Question 10

What is aneuploidy?

Answer 10

Some additional or missing chromosome

Question 11

What is monosomy?

Answer 11

One chromosome missing

Question 12

What is trisomy?

Answer 12

one extra chromosome

Question 13

What is polyploidy common in?

Answer 13

Plants

Question 14

What is the cause of aneuploidy?

Answer 14

Non-disjunction during meiosis

Question 15

What is aneuploidy common in?

Answer 15

Human contraception

Question 16

What does aneuploidy lead to?

Answer 16

Embryonic death or spontaneous abortion

Question 17

What is the only autosomal aneuploidy that permits survival into adulthood?

Answer 17

Down’s Syndrome (Trisomy 21)

Question 18

What are characteristics of Down’s syndrome?

Answer 18

Short stature
Sterile
Mental retardation
Heart defects

Question 19

What types of screening can you have for chromosomal abnormalities?

Answer 19

Amniocentesis and karyotyping
Blood tests to detect specific proteins associated with Downs foetus
Ultrasound scans

Question 20

What is the only viable human monosomy?

Answer 20

Turner’s syndrome (45,XO)

Question 21

What are the characteristics of Turner’s Syndrome?

Answer 21

Phenotypically female
Sterile due to lack of sex organs
Normal intelligence

Question 22

What is Klinefelters sysdrome?

Answer 22

(47,XXY)

Question 23

What are characteristics of Klinefelters?

Answer 23

Male with some female characteristics
Tall stature
Sub normal intelligence

Question 24

What chromosome determines if a human is male?

Answer 24

Y eg. XXXY is still male

Question 25

What is chi-du-chat syndrome?

Answer 25

Deletion of part of the short arm of chromosome 5

Question 26

What are characteristics of cri-du-chat syndrome?

Answer 26

Cat like cry
Defects in glottis and larynx
Retardation
Wide face and saddle nose

Question 27

What is Prader-Willi syndrome?

Answer 27

Deletion in long arm of chr 15

Question 28

What are features of Prader-Willi syndrome?

Answer 28

Obesity
Diabetes
Uncontrolled eating

Question 29

When does Angelmans syndrome arise?

Answer 29

If the same segment is missing from the maternally derived chromosome 15

Question 30

What are characteristics of angelmans syndrome?

Answer 30

Happy demeanor
Outbursts of laughter 
Mental retardation
Speech problems
Stiff limbs

Question 31

When does Prader Willis syndrome occur?

Answer 31

When the affected chromosome is inherited from the father

Question 32

What is familial Down’s syndrome?

Answer 32

Translocation carrier t(14;21): one of the chr 21’s is attached to one of the chr 14s

Question 33

What are the two syndrome that arise from translocation of chromosomes?

Answer 33

Familial Downs syndrome

Chronic myelotic leukaemia

Question 34

How does chronic myelocytic leukaemia cause leaukameia?

Answer 34

Translocation creates the BCR-ABL fusion gene - an

oncogene that stimulates over-production of white blood cells