Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ESA 1 - MCBG > Chromosomal Abnormalities > Flashcards

Chromosomal Abnormalities Flashcards

1
Q

What are the 2 major types of numerical cytogenic abnormalities?

A
  • Aneuploidy

- Polyploidy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is aneuploidy?

A

Abnormal number of chromosomes in a cell due to loss/gain of whole chromosomes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the 2 types of aneuploidy? Give clinical examples of each.

A

Trisomies

  • Down syndrome (21)
  • Edwards syndrome (18)
  • Patau syndrome (13)

Monosomies
- Turner syndrome (45,X) - only full monosomy syndrome to be viable.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the effects of meiotic non-disjunction for zygotes?

A

Non-disjunction in meiosis I (100% screwed)

  • 2 trisomic zygotes
  • 2 monosomic zygotes

Non-disjunction in meiosis II (50% screwed)

  • 2 OK zygotes
  • 1 trisomic zygote
  • 1 monosomic zygote
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Suggest a cause for meiotic non-disjunction.

A
  • Anaphase lag = chromosome can be “left-behind” at cell division because of defects in spindle function or attachment to chromosomes.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the result of mitotic non-disjunction during cell division in the zygote?

A

Mosaicism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is polyploidy, and what is its most common cause?

A
  • Gain of a whole haploid set of chromosomes, i.e. Triploidy 3n (69,XXX).
  • Polyspermy.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Name 4 examples of cytogenic structural abnormalities.

A
  1. Translocations
  2. Deletions
  3. Duplications
  4. Inversions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the cause of chromosomal deletions and duplications?

A

Arise through uneven pairing and recombination.

  • 2 gametes OK
  • 1 gamete with duplication
  • 1 gamete with deletion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the difference between balanced and unbalanced chromosomal rearrangements?

A
  • Balanced = no loss of genetic information (e.g. In many inversions)
  • Unbalanced = loss of genetic information
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the 2 types of translocation?

A
  1. Reciprocal translocation

2. Robertsonian translocation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the causes for reciprocal and robertsonian translocations?

A

Reciprocal
- 2 break rearrangement (involving 2 chromosome ends breaking and switching)

Robertsonian

  • q arms of 2 acrocentric chromosomes fuse together (loss of p arms)
  • can involve homologous or heterologous fusion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What structure do reciprocal translocations form at meiosis 1 metaphase?

A

Quadrivalent (instead of bivalent)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe the types of segregation occurring in meiosis 1 of reciprocally translocated chromosomes.

A
  1. Alternate
    - 1 normal balanced gamete
    - 1 translocated balanced gamete
  2. Adjacent 1 (non-homologous centromeres)
    - 2 unbalanced gametes
  3. Adjacent 2 (homologous centromeres)
    - 2 unbalanced gametes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Is adjacent 1 or 2 segregation more likely to occur in reciprocal translocations?

A
  • Adjacent 1.

- Adjacent 2 is very rare - causes large degree of imbalance.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What kind of structure is formed in metaphase of meiosis 1 in robertsonian translocations?

A

Trivalent (instead of divalent)

17
Q

What kind of gametes are formed from a homologous fusion resulting in Robertsonian translocation?

A

Always results in trisomies as:

  • 1 gamete gets the 2 fused homologs
  • 1 gamete gets nothing - non-viable
18
Q

What kind of gametes are formed from a heterologous fusion resulting in Robertsonian translocation?

A

Gametes will either contain

  • 2 normal chromosomes: balanced
  • fused chromosomes: balanced
  • fused chromosome + 1 normal: unbalanced
  • just normal chromosome: non-viable
19
Q

What are uniparental disomies?

A

Presence of chromosomes from 1 parent only.

20
Q

What are the different types of UPDs?

A
  1. Isodisomy: 2 identical chromosomes from 1 parent (error in meiosis II)
  2. Heterodisomy: 2 homologous chromosomes from 1 parent (error in meiosis I)
  3. Segmental UPD: only part of chromosome involved
  4. Acquired UPD: solid tumours and leukaemias
21
Q

Why does UPD matter?

A
  • Because of genomic imprinting: in some genes, only 1 allele is active depending on parent of origin (determined via epigenetics/methylation).
  • Most genes aren’t imprinted so most UPDs have no effect. But a person with UPD may lack any active copy of a gene undergoing genomic imprinting - loss of gene function.
  • Can lead to delayed development, intellectual disability, etc.
22
Q

Give 3 examples of UPD syndromes.

A
  1. Prader-Willi syndrome
    - uncontrolled eating and obesity
    - UPD on chromosome 15 (loss of paternal chromo)
  2. Angelman syndrome
    - intellectual disability and impaired speech
    - UPD on chromosome 15 (loss of maternal chromo)
  3. Beckwith-Widemann syndrome
    - accelerated growth and increased risk of cancerous tumours
    - UPD on chromosome 11
23
Q

Which 4 main mechanisms can generate UPD? Which is the most common?

A
  1. Trisomic rescue (most common)
  2. Gamete complementation
  3. Monosomic rescue (+ endoduplication)
  4. Postfertilisation error (+ endoduplication)
24
Q

How likely is trisomic rescue to lead to UPD?

A

1/3

25
Q

Why are UPDs rare?

A

Each mechanism generating a UPD requires 2 separate abnormal events.

ESA 1 - MCBG (23 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions