Unit 2-Lesson 2 Flashcards
What is meiosis?
2 cell divisions that produce 4 haploid cells
What happens in Meiosis I and Meiosis II?
- Meiosis I: reproduction division
- Meiosis II: separation of chromatids get haploid cells
How many chromosomes does a human cell have?
Human cells contains 46 chromosomes: diploid (2n)
How many chromosomes does a Gamete cell have?
Gametes have 23 chromosomes: haploid (n)
What happens when you combine a male gamete (sperm) with a female gamete (egg)?
23 chromosomes male gamete (sperm) + 23 chromosome female gamete (egg) = 46 chromosome zygote
Why is Meiosis important?
- It allows for sexual reproduction, which is important because…
- It allows for greater range of characteristics
- It ensures the recombination of genes
What happens in the Prophase I stage?
- Nuclear membrane dissolves
- Centrioles move to opposite poles
- Homologous chromosomes form a tetrad (group of 4)
- Homologous chromosomes align (matching chromosome) - synapsis
- Chromatids exchange segments - crossing over
What happens in the Metaphase I stage?
- Spindle fibre forms
- Homologous pairs attach to spindle
- Line up at the equatorial plate (middle of cell)
What happens in the Anaphase I stage?
- Homologous chromosomes move to opposite poles
- Each side gets 23 chromosomes - they are now (46 chromatids a singular chromsome)
What happens in the Telophase I stage?
- Cytoplasm divides forming 2 cells
- Each new cell is now haploid (23 chromosomes - and 46 chromatids)
- Nuclear membrane reappears
What happens in the Prophase II stage?
- Nuclear membrane dissolves
- Spindle fibres begin to form
What happens in the Metaphase II stage?
Chromosomes line up along the equatorial plate (the middle of the cell)
What happens in the Telophase II stage?
- Cytoplasm divides and nuclear membrane appears
- Meiotic division is complete with four daughter cells with 23 chromosomes
What happens in the Anaphase II stage?
Chromatids move to opposite poles (23 chromatids)
