Chromosome Variation and Structure Flashcards
Down’s Syndrome
Trisomy 21
Cause of aneuploidy
Nondisjunction in mitosis, meiosis I, or meiosis II
Nullisomy
Loss of both members of a homologous pair of chromosomes 2n - 2
Monosomy
Loss of a single chromosome 2n - 1
Trisomy
Gain of a single chromosome 2n + 1
Tetrasomy
Gain of two homologous chromosomes 2n + 2
Trisomy 18
Edward Syndrome 1/8,000 live births
Trisomy 13
Patau Syndrome 1/15,000 live births
Trisomy 8
1/25,000 - 1/50,000 live births
Robertsonian translocation
The short arm of one acrocentric chromosome is exchanged with the long arm of another.
Positive supercoiling
DNA is overrotated and the helix twists in on itself
Negative supercoiling
DNA is underrotated and the helix twists in on itself in the opposite direction
Nucleosome
DNA packaged around a histone
Telomere
Prevent nucleases from chewing the ends of chromosomes
Transposable element
DNA sequence that can move around in the genome, causing duplications, deletions and other rearrangements.