MBG: BLOCK 2: TOPIC 4: CHROMOSOME STRUCTURAL ABNORMALITIES

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Questions and Answers

What are the potential outcomes of deletions and duplications in paired mosaicism if the rearrangement occurs during the initial division?

All cells will exhibit either deletions or duplications that are complementary. (correct)

All cell lines will be normal.

Mosaicism will be less dynamic.

Only some cell lines will exhibit deletions.

In individuals with deletions and duplications, what happens during subsequent meiosis?

Rearrangements prevent any meiotic activity.

Loops form to maximize alignment. (correct)

Normal cell lines completely dominate the outcome.

Only deletions are retained.

Which syndrome is specifically associated with a microdeletion of approximately 1.5 Mb in chromosome 7?

Down Syndrome

Williams Syndrome (correct)

Prader-Willi Syndrome

Angelman Syndrome

What is a common effect of duplications relative to their corresponding deletions?

They can lead to the opposite phenotype of deletions. Signup and view all the answers

What is a possible consequence of dynamic mosaicism arising from deletions and duplications?

Stronger cell lines will completely replace less viable lines. Signup and view all the answers

What is the term for acquiring a telomere from another chromosome?

Telomere capture Signup and view all the answers

What is a potential result of gonadal mosaicism in a parent?

Increased likelihood of a genetic disorder Signup and view all the answers

Which type of deletion involves a loss at both the terminal ends of a chromosome?

Terminal deletion Signup and view all the answers

What kind of duplication has the same orientation as the original genomic segment?

Tandem duplication Signup and view all the answers

In paired deletions and duplications, which statement is true about their phenotypes?

Phenotypes of duplications are less severe than those of deletions. Signup and view all the answers

What can be a consequence of balanced familial structural rearrangements?

High incidence of infertility Signup and view all the answers

Which best describes pseudodominance?

Appearance of a recessive phenotype when the dominant allele is absent Signup and view all the answers

What is a characteristic of deletions in chromosomal rearrangements?

Haploinsufficiency can occur due to the loss of one gene copy Signup and view all the answers

How are deletions and duplications related in genomic alterations?

Dels and dups can be paired rearrangements within the same individual Signup and view all the answers

What is the significance of deletion size in relation to phenotypes?

The size of the deletion correlates with the presence and severity of the phenotype Signup and view all the answers

Which of the following syndromes is associated with specific deletion syndromes?

Prader-Willi Syndrome Signup and view all the answers

What impact do meiotic consequences of deletions and duplications have?

They can result in gametes with abnormal chromosomal structures Signup and view all the answers

Which type of deletion occurs within the chromosome, resulting in a segment being lost?

Interstitial deletion Signup and view all the answers

Study Notes

Deletions & Duplications

Deletions & duplications are the most common class of clinical chromosomal rearrangements
Postzygotic mitoses can produce paired deletions and duplications
Paired deletions and duplications can be complementary if rearrangement occurs in the initial division
If the rearrangement occurs later in the divisions, there is potential for normal cell lines to be present
Cell lines of lesser viability may be lost
Duplications have the potential to have the opposite phenotype of their deletion counterparts
Duplications are an extra copy of a genomic segment, resulting in partial trisomy
Duplications can be pure or combined with other rearrangements
Tandem duplications are contiguous doublings of a segment
Tandem duplications can be direct or inverted
Direct tandem duplications are the most common form of detectable tandem duplications in humans
Phenotypes of duplications are less severe than deletions
Meiosis in individuals with deletions and duplications results in loop formation to maximize alignment
Williams syndrome is caused by a ~1.5 Mb deletion on the long arm of chromosome 7
Williams syndrome impacts ~30 known and predicted genes, including ELN and LIMK1
Williams syndrome is associated with strengths in spoken language, music, and rote memorization, but difficulties with visual-spatial acuity
Microdeletions are associated with Williams syndrome, Prader-Willi and Angelman Syndromes

Classic Deletions

Terminal deletions have no discernable material beyond the site of breakage
Terminal deletions may retain a telomere through acquisition from other chromosomes or telomerase
Interstitial deletions have a proximal breakpoint and a more distal breakpoint after the missing material
Interstitial deletions have a continuation of the normal chromosome banding pattern

Familial Rearrangements

Balanced familial structural rearrangements can go generations without detection
Balanced familial rearrangements are typically associated with high incidence of infertility and multiple spontaneous pregnancy losses
Familial rearrangements are often unique/family-specific
Risk for abnormal phenotype is higher for an individual with de novo rearrangements than for an individual who has inherited a similar rearrangement from a parent

Consequences of Rearrangements

Rearrangements can result in loss or gain of gene activity, transcription, function, or protein-level activity
Pseudodominance is the appearance of a recessive trait due to loss of the dominant allele
Haploinsufficiency is the loss of one copy of a gene, with the remaining copy not enough to maintain full function

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Description

Test your knowledge on the mechanisms of genomic deletions and duplications. This quiz covers key concepts such as chromosomal rearrangements, paired deletions, and tandem duplications. Understand how these alterations affect phenotypes and cellular viability.