Unit 2 - Meiotic Division - Mar 17 Flashcards
Ploidy, examples
refers to the # of each chromosome that an organism carries. One set is designated ānā
Haploid: 1n
Diploid: 2n
Triploid: 3n
Mitosis vs Meiosis production
Mitosis: 2 identical daughter cells
Meiosis: 4 daughter cells, with half the genetic content of parent cell (2n parent->1n haploid daughter)
Zygote
a fertilized egg - a diploid cell that gives rise to all the cells of an organism
Reductive Division
When cells go from diploid to haploid in Meiosis 1. Meiosis occurs in 2 divisions called Meiosis 1 and 2.
Crossing Over
homologous recombination, each chromosome is joined at the exact same spot to the paired homolog, mixes up maternal and paternal alleles during Meiosis 1
Steps of Meiosis I
Interphase
Early Prophase 1 - chromosomes pair, spindle activates
Late Prophase 1 - nuclear envelope gone, spindle reach more, crossing over
Metaphase 1-crossed over pairs line up in middle
Anaphase 1-pairs pulled towards spindle (poles)
Telophase 1 + Cytokinesis-cell divides as haploid
Bivalents
homologous pair of chromosomes which form during early prophase 1
Meiosis II Steps
Prophase II-2 haploid cells duplicate chromosomes to sister chromatids
Metaphase II-sister chromatids line up in middle
Anaphase II-pulled apart
Telophase II + Cytokinesis-4 haploid cells
Somatic Cells
cell that only do mitosis, vast majority of human body
The Key to remembering the difference between meiosis and mitosis
homologous chromosomes only pair in meiosis,
homologous chromosomes ignore each other in mitosis
Nondisjunction
chromosome segregation errors, either homologous chromosomes or sister chromatids can fail to separate
Aneuploid
a cell with abnormal chromosome number