Eukaryotic Meiosis Flashcards
Why do we need a unique process from mitosis to create gametes?
We need sex cells with the haploid number of chromosomes so when they fertilize the resultant offspring has the diploid number
What are the two stages of meiosis?
- Meiosis I
- Meiosis II
What are the phases of Meiosis I?
- Prophase I
- Metaphase I
- Anaphase I
- Telophase I and cytokinesis
What occurs during prophase I (meiosis)?
- homologous chromosomes align and synapse
- crossing over between non sister chromatids occurs at chiasmata
- crossing over results in chromatids now being a mix of pieces from maternal and paternal chromosome
What occurs during Metaphase I (meiosis)
- paired homologous chromosomes move to metaphase plate
- chiasmata ( not kinetochores) line up on metaphase plate
What occurs during anaphase I ( meiosis)
- recombined homologous chromosomes separate in a process called disjunction
- sister chromatids remain together
- chromosomes are randomly organized into different poles ( not based off maternal/ paternal)
What occurs during Telophase I and Cytokinesis (meiosis)?
- cell divides at cleavage furrow
- haploid cells with duplicated chromosomes (pairs of chromatids) form
- haploid because only half of genetic information is in each cell
What are the stages of Meiosis II?
- Prophase II
- Metaphase II
- Anaphase II
- Telophase II and cytokinesis
What occurs at Prophase II ( meiosis)?
- nuclear envelope fragments
- spindle begins to form
What happens during Metaphase II (meiosis)
- Sister chromatids line up at center of cell and microtubules attach to kinetochores and to centrioles and opposites poles of the cell
What happens during Anaphase II ( meiosis)
- sister chromatids disjoin and are pulled to opposite ends of cell
What happens during Telophase II and cytokinesis (meiosis)
- nuclear envelope reforms
- cell divides to form haploid daughter cells
What are the differences between mitosis and meiosis I? (4)
- chromosomes align at center of cell independently in mitosis but in meiosis the homologous chromosomes synapse and cross over
- in mitosis the centromeres line up on metaphase plate, in meiosis the chiasmata lines up on metaphase plate
- chromatids disjoin in mitosis, chromosomes disjoin in meiosis
- daughter cells are diploid vs haploid
What are 3 ways that sexual reproduction produces genetic diversity?
- independent assortment of chromosomes
- crossing over
- random fertilization of gametes
How is genetic diversity beneficial to a population?
Allows natural selection to create a stronger and more adaptable population
