Chromosomal Abnormalities

Question 1

• Key differences between meiosis and mitosis? (2) Centromeres divide when for each?
• How can crossover effect nondisjunction? (2)
• Trisomies of often related to nondisjunction when?

Answer 1

• Homologues link and crossing over occurs; Mitosis = A1; Meiosis = A2
• 1.) Occurs too close or far away leading which may create
  2. ) too many or little crossovers make it hard to disjunction
• Meiosis 1 non disjunction

Question 2

Trisomy examples: (3)

Answer 2

1. ) 21 = Downs - hypotonia, congenital heart issues
2. ) 18 = Edwards - hand positioning, intrauterine hernias
3. ) 13 = Patau - Renal issues, facial cleft, holoprosencephaly

Question 3

• Pseudoautosomal regions?
• M1 splitting? M2 Splitting?
• Nondisjunction in M1 leads to? M2?
• Acrocentric chromosome made up of? (2)

Answer 3

• X and Y line up
• 2 gametes = n+1; 2 = n-1
  2 gametes = n; 1=n+1 and 1=n-1
• stalk of rRNA and a satelite of repeats

Question 4

• Polypleudy examples? (2)
• Anueplouidy can occur because?
• 3 examples of aneupluedy?
• Mosiaicism: definition? occurs because? severity depends on?

Answer 4

• 3n = 2 sperm; 4n = DNA duplication without division
• xxy = klinefelters; tall, hypogonaism, infertile
• xyy = xyy syndrome = typically indistinguishable
• xo = tuerners - webbed neck, sterile, broad chest
• 2 cell lines with different chormosome #’s, non disjunction in early mitotic division, timing of non d

Question 5

• Rearrangements are common with?
• 2 types? Def?
• B: 1? 2 types? Crossing over creates 4 types of gametes for the 2 types?
  2.? Def? Type of allignment? Types of disjunction?
  3? Def? Can lead to what disease? 6 possibilities with disjunction?

Answer 5

• DS breaks and crossing over
  1. ) Balanced = normal but rearranged
  2. ) Unbalanced = non normal

1. ) Inversion: Paracentric (exclude centromere) = 4 gametes –> normal, inverted, dup, del or pericentric (include centromere) = normal, inverted, dicentric (2 centromeres), accentric
2. ) Reciprocal translocation = recombination of 2 non homologous chromosomes; quadravalence allignment; alternative (1 normal, 1 balanced), adjacent 1 or 2 (2 unbalanced)
3. ) Robertsonian translocation: fusion of 2 long arms of acocentric chromosomes; downs; (normal, balanced, downs, 3 lethal variations)

Question 6

• Unbalanced:
  1. ) Deletion: 2 types? def?
  2. ) Duplication: Lethality?
  3. ) Isochromosomes: Def? where does it often occur? chance of abnormal progeny? why?
  4. ) Marker (ring) chromosomes: occur why?

Answer 6

1.) Terminal = deleted fragment makes chromosome non transmissible (no centromere)
Interstitial = contains centromere and makes ring

2. ) Generally less
3. ) One arm is missing and is mirrored; 21 or x; 100% b/c they either have 3 copies or none
4. ) Interstitial deletion

Question 7

• Contiguous gene syndromes: Def? Ex? (2)
• Example of duplication disorder? Symptoms?
• Example of deletion disorder?

Answer 7

• Disorder due to over expression or deletion of multiple loci adjacent to each other; velocardial facial and Digeorge
• Carcot-Marie Tooth = Dup of 17; hammer toes/foot weakness; neurological disorder
• HNPP (Heriditary neuropathy with Pressure Palsies = Deletion of part of 17