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MCBG > MCBG S12 Chromosome Mutations > Flashcards

MCBG S12 Chromosome Mutations Flashcards

1
Q

What is cytogenetics?

A

The study of the genetic constitution of cells through the visualisation and analysis of chromosomes.

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2
Q

Why do we do cytogenetic analysis?

A
  • Provide diagnosis and prognosis of clinical problems
  • Better clinical management
  • Assess reproductive risks.
  • Prenatal diagnosis
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3
Q

What are the 2 main reasons for referral to cytogenetics department?

A

People with abnormalities since birth

People with acquired abnormalities as part of the disease proves

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4
Q

What are 2 methods of prenatal diagnosis?

A

Chorionic villus sampling

Amniocentesis

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5
Q

What is the risk of prenatal diagnosis?

A

Miscarriage risk.

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6
Q

What is involved in prenatal diagnosis?

A

Needed guided under US - invasive methods.

Biochemical markers tested for.

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7
Q

What are some birth defect types?

A 
Dysmorphism 
Mental retardation 
Congenital malformations
Developmental delay
Specific syndromes.
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8
Q

What testing method is mainly used in cytogenetic analysis?

A

Karyotyping

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9
Q

What is the karyotyping nomenclature?

A

Number of chromosomes, sex Complement and structure changes seperated by commas

NO SPACES

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10
Q

What is mosaicism?

A

2 cell lineages/populations in an individual

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11
Q

What causes anueploidy?

A

Non-disjunction in Meiosis.

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12
Q

What is polyploidy?

A

Gain of haploid set of chromosomes.

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13
Q

What is the most common cause of polyploidy?

A

Polyspermy

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14
Q

What extra chromosomes confer viability of life, in terms of anueploidy?

A

13
18
21

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15
Q

What missing chromosomes still allow for viability of life and why?

A

X chromosomes

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16
Q

What are the symptoms of trisomy 21, Down syndrome?

A

Hypertonic
Characteristic facial features
Intellectual disability
Heart defects

17
Q

What are the symptoms of trisomy 18 Edward syndrome?

A 
Smaller lower jaw
Prominent occiput 
Lower set ears
Rocker bottom feet
Over-lapping fingers

SPLRO

18
Q

What are the symptoms of trisomy 13, Patau syndrome?

A

Polydactyl
Holoproscencephaly - multiple cleft palates
Die in neonatal period

19
Q

What are symptoms of Turner syndrome?

A 
Puffy feet
Redundant skin and back of neck
Short stature
Heart defects
Mild learning difficulties 
Neck webbing
Infertility
20
Q

Trisomic concept is may be rescued from trisomy 21 if _______ ____ occurs during division getting rid of the extra chromosome 21.

A

Anaphase lag

21
Q

Name some types of cytogenetic structural abnormalities.

A 
Translocations 
Inversions
Duplications
Deletion
Insertions
Rings
Isochromosomes
22
Q

What is a balanced translocation?

A

Translocation in which no chromosome material has been lost or gained.

23
Q

When can a balanced translocation cause a problem?

A

When they come to have children. Offspring can inherit an unbalanced form of the translocation.

24
Q

What is an unbalanced translocation?

A

When there has been loss or gain of genetic material as a result of a translocation

25
Q

What are the types of segregation in Meiosis I?

A

Alternate
Adjacent 1
Adjacent 2
3:1 non disjunction

26
Q

Describe alternate segregation at meiosis I.

A

Alternate centromere segregate together - normal/ balanced gametes form.

27
Q

Describe adjacent-1 segregation.

A

Non-homologous centromeres divide

Imbalanced gametes

28
Q

Describe adjacent 2 segregation?

A

Homologous centromeres segregates

Unbalanced gametes

29
Q

What is the most likely segregation to cause imbalance?

A

Adjacent 1

30
Q

What is a robertsonian translocation?

What chromosomes is it most common in?

A

2 acrocentric chromosomes fuse together and P arms are lost.

13,14,15,21 and 22 - Acrocentric

31
Q

Robertsonian translocations form ________ at meiosis I.

A

Trivalent

32
Q

What syndromes can occur as a result of unbalanced robertsonian translocation?

A

Patau syndrome - trisomy 15

Down syndrome - trisomy 21

33
Q

Name 4 types of FISH probe.

A

Locus/ gene specific probes
Telomere probes
Centromere probes
Whole chromosome paints.

34
Q

Why are centromere probes useful?

A

Used to identify the chromosome of origin, if there is a difference in the banding pattern.

35
Q

Why are locus/ gene specific probed useful?

A

Detect microdeletions and duplications.

36
Q

What are some advantages of aCGH?

A

High resolution genome examination
Target against specific genetic conditions
Info of deletions and duplications can be seen.

37
Q

What are disadvantages of aCGH?

A

More expensive than karyotyping
Not detect balanced rearrangements
Challenging to interpret whether change is pathogenic or due to variation.
Mosaicism can not be detected.

MCBG (9 decks)

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