Lecture 15: Errors in meiosis & X-activation Flashcards
nondisjunction is failure of chromosomes to
seperate properly during meiosis
Nondisjunction in the first stage of cell division results in what combination of gametes?
n+1, n+1, n-1, n-1
Nondisjunction in the second stage of cell division results in what combination of gametes?
n+1, n-1, n, n
People with Klinefelter syndrome possess what sex chromosomes?
XXY
What are the characteristics of Klinefelter syndrome?
Phenotypically male but possess many female characteristics
People with Turner syndrome possess what sex chromosomes?
XO
What is Turners syndrome?
The absence of a second X chromosome
What does aneuploid mean?
+/- 1 chromosome
What is deletion?
The removal of a chromosomal segment from DNA
What is inversion?
The inverting of a chromosomal segment, meaning it is reversed in the chain e.g. BCD turning to DCB
What is duplication?
The replication of a Chromosomal segment
What is translocation?
Moving a segment from one chromosome to a non homologous chromosome
What are Barr bodies?
They are an inactive X chromosome in a cell with more than 1 X chromosome
What can Barr bodies lead to?
They can lead to random inactivation through out the body of X chromosomes which possibly results in mosaic patterning
What causes familial Down syndrome?
Translocation of chromosome 21 segment with chromosome 14 segment
