Meiosis Flashcards
What is meiosis?
A form of nuclear division that results in the production of haploid cells from diploid cells
It produces gametes in plants and animals used in sexual reproduction.
How many divisions occur in meiosis?
Two divisions: meiosis I and meiosis II
What are the stages within each division of meiosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
What occurs during Prophase I of meiosis?
DNA condenses into visible chromosomes, homologous pairs form, crossing over may occur, and the nuclear envelope breaks down
What is crossing over?
The process by which nonsister chromatids exchange alleles during Prophase I
What is the significance of the chiasma?
It is the point at which crossing over occurs between homologous chromosomes
What happens during Metaphase I?
Homologous chromosomes line up along the equator of the spindle, with spindle fibers attached to the centromeres
What occurs during Anaphase I?
Homologous pairs of chromosomes are separated and pulled to opposite ends of the spindle
What is the end product of cytokinesis in meiosis I?
Two haploid cells
What is unique about meiosis II compared to meiosis I?
There is no interphase between meiosis I and meiosis II, so DNA is not replicated
What happens during Telophase II?
Nuclear membranes form around each group of chromosomes and cytokinesis occurs, resulting in four haploid cells
What is the difference between mitosis and meiosis?
- Mitosis: One division, two identical daughter cells, somatic cells
- Meiosis: Two divisions, four genetically different daughter cells, gametes
What are the similarities between mitosis and meiosis?
- Both start from a diploid cell
- Both consist of prophase, metaphase, anaphase, and telophase
- Chromosomes line up along the equator in metaphase
- Chromosomes separate to the poles in anaphase
- Both end with cytokinesis
What is independent assortment?
The random orientation of homologous pairs during metaphase I leading to different combinations of alleles in daughter cells
What is the formula to calculate the number of possible chromosomal combinations resulting from meiosis?
2^n, where n is the number of homologous chromosome pairs
How many different chromosomal combinations can occur in humans?
8,388,608 possible combinations (2^23)
What is the formula for random fertilization of two gametes?
(2n)²
How many combinations of chromosomes occur after fertilization in humans?
70,368,744,177,664 combinations
True or False: Meiosis produces genetically identical gametes.
False
What is the importance of meiosis in sexual reproduction?
It allows for the fusion of gametes and ensures genetic diversity among offspring
What is the role of mutations in genetic variation?
Mutations can lead to the production of new alleles and increased genetic variation
