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IMS- Strand 1 > Chromosomal abnormalities > Flashcards

Chromosomal abnormalities Flashcards

1
Q

How do you analyse chromosomes?

A

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

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2
Q

What should each chromosome contain?

A

P arm, Q arm and centromere

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3
Q

How do scientists identify chromosomes?

A

1- Size
2- Banding pattern
3- Centromere position

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4
Q

What are acrocentric chromosomes?

A

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

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5
Q

What is a normal female karyotype?

A

22 pairs XX

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6
Q

What is a normal male karyotype?

A

22 pairs XY

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7
Q

What abnormalities can be picked up on a karyotype?

A
  • Abnormal chromosome number
  • Abnormal chromosome material location
  • Abnormal amounts of chromosome material (bits missing or extra)
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8
Q

What are the 3 main types of chromosomal abnormalities?

A

Aneuploidies
Microdeletions
Translocations

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9
Q

What is aneuploidy?

A

Abnormal number of copies of an individual chromosome

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10
Q

What is Monosomy?

A

1 chromosome missing, Total= 45

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11
Q

What is Trisomy?

A

1 chromosome extra, Total= 47

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12
Q

What is polyploidy?

A

Abnormal number of sets of chromosomes

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13
Q

What is Monoploid?

A

One set, Total= 23 pairs

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14
Q

What is Diploid?

A

Two sets, Total= 46 pairs

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15
Q

What is Triploid?

A

Three sets, Total= 69 pairs

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16
Q

What are deletions?

A

Loss of a segment of genetic material from a chromosome

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17
Q

What are duplications?

A

Gain of a segment of genetic material from a chromosome

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18
Q

What are microdeletions/ microduplications?

A

too small to be seen on a karyotype

19
Q

What is the consequence of deletions & duplications?

A

depends on which genes are in the deleted/ duplicated region

20
Q

What is a translocation?

A

Relocation of chromosome material to the wrong place

21
Q

What is a reciprocal translocation?

A

2 different chromosomes have exchanged segments with each other

22
Q

What is a Robertsonian translocation?

A

An entire acrocentric chromosome attaches to another at the centromere

23
Q

What is a balanced translocation?

A

All chromosome material present (just in the wrong place)

24
Q

What is an unbalanced translocation?

A

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

25
Q

What is down syndrome?

A

Trisomy 21 (3 copies of chromosome 21)

26
Q

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

A
  • Characteristic facial features
  • Mild= moderate intellectual disability
  • Short stature
  • Congenital heart disease
  • Endocrine problems
  • Increased risk of leukaemia and Alzheimer’s
27
Q

What are 10 phenotypic changes associated with Down’s syndrome?

A
  • Up-slanting palpebral fissues
  • Prominent epicanthic folds
  • Flat nasal bridge/ flat facial profile
  • Low set small ears
  • Furrowed tongue
  • Single transverse palmer crease
  • Clinodactyly
  • Brushfield spots
  • Sandal- toe deformity
  • Excess nuchal skin
28
Q

What is Edward’s Syndrome?

A

trisomy 18

29
Q

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

A
  • Intra-uterine growth restriction
  • Most die during pregnancy/ neonatal period
  • Overlapping fingers
  • Rocker-bottom feet
  • Congenital heart/kidney disease
  • Small head size (microcephaly)
30
Q

What is Patau’s syndrome?

A

Trisomy 13

31
Q

What are 6 clinical features of Patau’s syndrome?

A
  • Intra-uterine growth restriction
  • Most die during pregnancy/ neonatal period
  • Cleft lip/ palate
  • Extra fingers/ toes
  • Brain abnormalities
  • Congenital heart disease
32
Q

What is Antenatal combined screening?

A

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

33
Q

What is Klinefelter syndrome?

A

47 XXY

34
Q

What are 4 clinical features of Klinefelters syndrome?

A
  • Tall stature
  • Normal intellect
  • Infertile- often diagnosed in a fertility clinic
  • Little facial/ body hair
35
Q

What is Turner syndrome?

A

Monosomy X (45, XO)

36
Q

What are the 7 clinical features of Turner syndrome?

A
  • Infertility
  • Short stature
  • Lymphoedema (puffy hands and feet)
  • Webbed neck
  • Endocrine abnormalities
  • Congenital heart disease
  • Normal intellect
37
Q

What is Di George syndrome?

A

22q11.2 microdeletion

38
Q

What are 6 clinical features of Di George syndrome?

A
  • Congenital heart and Kidney disease
  • Nasal speech
  • Characteristic facial features
  • Hypocalcaemia
  • Intellectual disability (mild- severe)
  • Increased risk of psychiatric disorders
39
Q

What is Prader Willi syndrome?

A

15q11.2-q13 microdeletion most common mechanism

40
Q

What are 6 clinical features of Prader Willi syndrome?

A
  • Low tone at birth
  • Short stature
  • Characteristic facial features
  • Challenging behaviours + hyperphagia
  • Intellectual disability
  • Absent/ incomplete pubertal development
41
Q

How is Chronic myeloid leukaemia caused?

A
  • Reciprical translocation between chromosomes 9 and 22 resulting in the Philadelphia chromosome
    -BCR gene from chromosome 22 fuses with ABL gene from chr9 creating a fusion oncogene called BCR::ABL
42
Q

What does BCR::ABL do?

A
  • Directs production of mutant protein which drives conversion of normal bone marrow stem cells into leukaemic cells
43
Q

What are balanced reciprocal translocations associated with?

A

Recurrent miscarriage and multiple congenital anomalies

44
Q

What do robertsonian translocations involving chromosome 21 cause?

A

Recurrent miscarriage and recurrent down syndrome

IMS- Strand 1 (4 decks)

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