Meiosis, Gamete Formation Flashcards
How many stages of Meiosis are there? What are they?
- Meiosis I and Meiosis II
What happens before Meiosis I?
All chromosomes duplicate
What happens to the nuclear membrane during Prophase I?
It breaks down
What happens w/ the spindle fibers during Prophase I?
They start to form
What happens in Prophase I with the replicated chromosomes?
Each replicated chromosome joins with its pair to form a group of four sister chromatids
What is the group of chromosomes formed in Prophase I called?
A tetrad
What is the pairing process that forms tetrads in Prophase I called?
Synapsis
What may happen to the homologous chromosomes while the chromosomes are in tetrad formation?
Twist around each other and exchange segments of chromosomes
What is the segment exchange between chromosomes during synapsis called?
crossing over
What happens to the chromosomes during Metaphase I?
They line up in the center of the cell in tetrad formation
What happens to the spindle fibers during Metaphase I? Where?
They attach to the tetrads at their centromeres
What is disjunction?
When the homologous pairs separate and move to opposite sides of the cell.
When does disjunction happen?
Anaphase I
The two cells that result from Meiosis I are diploid or haploid?
Haploid
Why does the cell need to divide again after Meiosis I?
Because the chromosomes are each still double stranded.
What happens during Telophase I and Cytokinesis?
The cell divides into two new, haploid cells
How many chromosomes do the two cells that resulted from Meiosis I have?
Half the number of chromosomes as the original
What happens during Prophase II?
Each daughter cell forms spindle fibers and the chromosomes move toward the middle of the cell
What happens during Metaphase II?
The chromosomes line up in the center, one by one, of both daughter cells and the spindle fibers attach to their centromeres
What happens during Anaphase II?
The two chromatids separate, each becoming a single stranded chromosome and they move to opposite sides of the cell
What happens to the nuclear membrane during Telophase II/Cytokinesis?
It reforms