University:
University Of Illinois at Chicago
Course:
BIOS 220 | Genetics
Academic year:

2021
Views:

444

Pages:

9
Author:

Hallie Randolph

Reciprocal Translocation Adjacent-1 segregation: homologous centromeres separate at anaphase I; gametes contain duplications and deletions Translocation Quadrivalent in Meiosis Unbalanced Adjacent is defined by centromeres next to each other around the quadrivalent Adjacent-2 has homologous centromeres together Adjacent-2 Unbalanced Reciprocal Translocation Adjacent-2 segregation: homologous centromeres stay together at anaphase I; gametes have a segment duplication and deletion Translocation Quadrivalent in Meiosis Tertiary trisomy: 2 normal and 1 translocation Tertiary monosomy 3:1 combinations can have varying outcomes but frequently involve trisomies and monosomies It is also known as 3:1 nondisjunction Interchange trisomy: More RARE Interchange monosomy Translocation Quadrivalent in are actually 4, 3:1 Meiosis There options Interchange trisomy option 2 Interchange monosomy option 2 Tertiary trisomy option 2 Tertiary monosomy option 2 Translocation Quadrivalent in Meiosis: 4, 0 segregation 4:0 = all chromosomes to one cell Gametogenesis and Meiotic Outcomes Spermatogenesis ◦ Alternate (44%) and adjacent 1 (31%) are predominant forms ◦ Adjacent 2 (13%), 3:1 (11%), and 4:0 (rarely) Oogenesis ◦ Data is more problematic and variable ◦ Likely exhibits age-related effects complicating the analysis of meiotic outcomes Acrocentric chromosomes exhibit different patterns due to marked asymmetry of the quadrivalent ◦ Fewer alternate segregants and more 3:1 have been observed Viability Correlates with genes involved and severity of information lost/gained Severe forms undergo spontaneous pregnancy loss perhaps even prior to implantation (common?) Usually the sole survivable imbalance is a partial trisomy Viable offspring outcomes ◦ 71% derived from adjacent-1 ◦ 4% derived from adjacent-2 ◦ 22% tertiary trisomy/monosomy ◦ 2.5% interchange trisomy Check-in Questions Centromeric fusion of acrocentric chromosomes can referred to as a(n) __________. A. Robertsonian translocation B. Centromeric recombinant C. Reciprocal translocation D. Isochromosome formation This segregation pattern following formation of the quadrivalent has two homologous centromeres end up together in the same daughter cell without an increase in number of chromosomes. A. What is alternative segregation? B. What is adjacent-1 segregation? C. What is adjacent-2 segregation? D. What is 3-1 segregation? E. What is 4-0 segregation?