meiosis phases 1 and 2 Flashcards
Why is meiosis important?
It ensures the chromosome number stays constant across generations and creates genetic variation
Where does meiosis occur in animals and plants?
In animals, it happens in the ovaries and testes. In plants, it occurs in the anther and ovule.
How many chromosomes do humans have?
46 chromosomes (23 pairs).
What does PMAT stand for in meiosis?
Prophase – Chromosomes Pair up (crossing over).
Metaphase – Chromosomes move to the Middle.
Anaphase – Chromosomes move Apart.
Telophase – Terminal phase where cells split.
What is crossing over, and why is it important?
It is the exchange of genetic material between homologous chromosomes, leading to genetic variation.
Differences Between Meiosis I and II
Meiosis I vs Meiosis II
1. Homologous chromosomes separate 2. Chromatids separate
1. Crossing over occurs 2. No crossing over
1. Produces 2 haploid cells 2. Produces 4 haploid cells
What happens during Prophase I of meiosis?
The nuclear membrane and nucleolus disappear.
Chromosomes condense and pair up to form homologous pairs (bivalents).
Crossing over occurs at the chiasma, exchanging genetic material.
Spindle fibers begin to form.
What happens during Metaphase I?
Homologous chromosome pairs align along the equator of the cell.
Chromosomes attach to spindle fibers.
Random arrangement occurs, increasing genetic variation.
What happens during Anaphase I?
Spindle fibers pull homologous chromosomes apart to opposite poles.
Each pole gets one complete set of chromosomes.
Chromatids remain attached at the centromere.
What happens during Telophase I and Cytokinesis?
A new nuclear membrane forms around chromosomes at each pole.
Cytoplasm divides (cytokinesis), forming two haploid daughter cells.
Each daughter cell has half the number of chromosomes.
What is the final result of meiosis?
Four genetically unique haploid cells are produced.
Each cell has half the number of chromosomes.
These cells are either gametes (sperm/egg) in animals or spores in plants.
