Meiosis Flashcards
what is meiosis?
a reductive division that converts a diploid cell into four haploid cells, each with one complete set of chromosomes
what is the need for meiosis in reproduction?
meiosis occurs during gamete formation , producing cells with half the normal number of chromosomes
gametes vs somatic cells
gametes are sex cells (egg & sperm) with two chromosomes each whereas somatic cells are all other non-productive cells with 4 chromosomes each
fertilization
the fusion of two haploid gametes results in a diploid zygote, which contains two sets of chromosomes
example of diploid and haploid
two sets of chromosomes are present in the somatic cells, making them diploid. one set of chromosomes is present in gametes, making them haploid.
sexual reproduction
reproduction that involves the alternation of meiosis and fertilization
germ-line cells
during zygote development, cells that are set aside from the somatic cells and that will eventually undergo meiosis to produce gametes.
the comparison of meiosis and mitosis
meiosis involves two nuclear divisions with no DNA replication between them. it produces four daughter cells with half the original amount of chromosomes. mitosis involves a single nuclear division after DNA replication. it produces two daughter cells, each containing the original number of chromosomes.
two distinct features of meiosis
- pairing of homologues and crossing over that joins maternal and paternal homologues.
- maintenance of sister chromatid cohesion at sister centromeres.
how does meiosis introduce genetic variation
independent assortment contributes new gene combinations to the next generation because the orientation of chromosomes on the metaphase plate is random. it is also increased by crossing over, or genetic recombination as this further shuffles the arrangements of genes on chromosomes.
