Brainscape's Knowledge GenomeTM

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


See full index

Clinical Genetics > Chromosomal abnormalities 2 > Flashcards

Chromosomal abnormalities 2 Flashcards

You may prefer our related Brainscape-certified flashcards:
Biology 101 flashcards
1
Q

Examples of structural abnormalities of chromosomes

A

-Translocations
-Reciprocal
-Robertsonian
-Inversion
-Deletion
-Duplication
Rings
Isochromosomes
-Microdeletions/
Microduplications

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

Steps involved in structural abnormalities arising in chromosomes

A
  • Double strand DNA breaks
  • Occur throughout cell cycle
  • Generally repaired through DNA repair pathways
  • Mis-repair leads to structural abnormalities
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is reciprocal translocation?

A

Exchange of two segments between non-homologous chromosomes

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

What is non homologous end joining(NHEJ) and how does it arise?

A

If there is a double stranded break, sometimes instead of being stuck back together appropriately, it finds another free end and sticks there

  - Stuck to the wrong chromosome 
  - Physical exchange between two non-homologous chromosomes  
 - Happens if they are physically close to one another
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is translocation?

A

Translocation is where we happen to have two double strands breaks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are translocation due to inappropriate NHEJ also known as?

A

Also known as balanced translocations

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

What is the key characteristic of balanced translocations?

A

The key characteristic is that there is no net gain or loss of genetic material – it’s all there, just in a different place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What chromosome is balanced translocation an example of?

A

Philadelphia chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the Philadelphia chromosome involved in?

A

Involved in causing chronic myeloid leukaemia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Formation of balanced translocation in philadelphia chromosome

A
  • Chr 9 has ABL proto-oncogene and Chr22 has BCR
  • BCR has tendency for double stranded breaks
  • Double stranded break causing exchange of material between 9 and 22
  • Causes a fusion gene and results in ABL going from being proto-oncogenic to oncogenic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is unbalanced translocation?

A

too much or too little of a particular chromosome

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

What are reciprocal translocations?

A

Exchange of two segments between non-homologous chromosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

When is there deleterious phenotypes in reciprocal translocations?

A

deleterious phenotype if breakpoint affects regulation of a gene

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

What are carriers of balanced translocations at risk of?

A

Carrier of balanced translocation at risk of producing unbalanced offspring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are individuals with unbalanced translocations at significant risk of?

A

Unbalanced individuals at significant risk of chromosomal disorder

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

How do you go from a balanced carrier to an unbalanced zygote?

A

Problems arise when gamete has one intact chromosome and one derivative chromosome

  • Zygote will then have an extra copy of one part of the intact chromosome
    - Becomes partially trisomic and partially monosomic
17
Q

What is reciprocal translocations?

A

no loss or gain of material and so there’s often little consequence to the cell of carrying a reciprocal translocation

18
Q

Steps involved in reciprocal translocation

A

SEE NOTES AND DIAGRAM

19
Q

What is the clinical results of unbalanced reciprocal translocation?

A
  • Many lead to miscarriage (hence why a woman with a high number of unexplained miscarriages should be screened for a balanced translocation)
  • Learning difficulties, physical disabilities
20
Q

What chromosomes do Robertsonian translocations involve?

A

Involve acrocentric chromosomes

-13, 14, 15, 21, 22

21
Q

What is a robertsonian translocation

?

A

Two acrocentric chromosomes break at or near their centromeres
-The fragments are joined together again it’s possible for just the two sets of long arms to be brought together and there’s loss of the satellites

22
Q

What is the most common robertsonian translocation?

A

Most common Robertsonian translocation involves chromosomes 13 and 14

23
Q

What does the robertsonian translocation of chromosomes 13 and 14 result in and what does the resultant chromosome contain?

A

Results in loss of two short arms and fusion of the two long arms, with either one or two centromeres
-The resultant chromosome usually contains the long arms of different chromosomes

24
Q

How many chromosomes does an individual who’s a balanced carrier involving a robertsonian translocation?

A

Balanced carrier has 45 chromosomes

25
Q

What does it mean if an individual has 46 chromosomes including robertsonian translocation?

A

If 46 chromosomes present including Robertsonian then must be unbalanced

26
Q

What do p arms encode?

A

p arms endoe rRNA

27
Q

What does a 21;21 robertsonian translocation lead to?

A

leads to 100% risk of Down syndrome in fetus

28
Q

What is the centromere?

A

Part of the chromosome which attaches to the spindle during cell division

29
Q

What is the only way a chromosome can be made stable if the end of the chromosome is lost?

A

If the end of the chromosome is lost then the only way the chromosome can be made stable is if a new telomere is added
-Without the telomere the cell will die

30
Q

What do interstitial deletions in chromosomes result in?

A
  • Prader-Willi
  • DiGeorge syndrome
  • Cri du chat
31
Q

What are inversions?

A

Where there are two breakpoints within the same chromosome and when these are repaired the middle section is “upside down”

32
Q

What is a ring chromosome?

A

Where you get two breaks in the same chromosome and that non-homologous end joining mechanism joins the two ends of the large chunk together, resulting in a ring

33
Q

What do deletions cause a region of?

A

Causes a region of monosomy

34
Q

What can gross deletions be seen on?

A

Gross deletions seen on metaphase spread on G-banded karyotype

35
Q

What can show micro deletions that traditional approaches can’t?

A

High resolution banding, FISH and now CGH showed ‘micro’ deletions

36
Q

What is contiguous gene syndrome?

A

Only a few genes may be lost or gained

37
Q

What can unequal crossing over lead to?

A

Unequal crossing over can lead to these microdeletions and microduplications

38
Q

What does array-CGH look at?

A

Looks at dosage

39
Q

What are the steps involved in array-CGH?

A
  1. Take healthy individual and affected individual DNA 2.These anneal to probes on glass array
    - Should be equal hybridisation
    - If both patient and control have two copies of a region (disomic) – 5 probes will have patient DNA and 5 will have healthy DNA = DOSAGE WILL BE EQUAL
    - If there is a microdeletion/microduplication in patient DNA i..e two copies in healthy DNA and one in patient DNA :
    - Dosage will be different
    - Hybridisation will be unequal

Clinical Genetics (4 decks)

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