Chapter 10 Meiosis Flashcards
Gametes
The male or female reproductive cell that contains half the genetic material of the organism
Meiosis
- A specialized type of cell division which reduces the chromosome number by half
- Meiosis occurs in all sexually reproducing eukaryotes (both single-called and multicellular) including animals, plants, and fungal
Somatic cells
Any cell of a living organism other than the reproductive cells
-one of the cells that take part in the formation of the body, becoming differentiated into the various tissues, organs, etc
Diploid chromosome number (2n)
The number of chromosomes present on each somatic cell, which is constant for any one species of plant or animal
Haploid chromosome number (n)
The number of chromosomes in a sperm or egg cell
-half the diploid number
Meiosis I phases
- prophase I
- metaphase I
- anaphase I
- telophase I
Meiosis II phases
Prophase II
Metaphase II
Anaphase II
Telophase II
Crossing over (a form of genetic recombination)
- the exchange of genetic material between homologous chromosomes that results in recombinant chromosomes
- one of the final phases of genetic recombination, which occurs during prophase I of meiosis during a process called synapsis
Tetrad
A group of four chromatids formed from each pair of homologous chromosomes that split longitudinally during the prophase of meiosis
Independent assortment
The process of random segregation and assortment of chromosomes during anaphase 1 of meiosis resulting in the production of genetically unique gametes
Sex chromosomes
- either of a pair of chromosomes that determine whether an individual is male or female
- the sex chromosomes of human beings and other mammals are designated by scientist as X and Y
- XX = female; XY = male
Oogonia
Any of the cells that give rise through mitosis to the oocytes and are found in the ovaries of vertebrates
Spermatagonia
Any of the cells that give rise through mitosis to the spermatocytes and are found in the testes of vertebrates
Primary oocytes
An oocyte that has begun but not completed the first meiotic division
-it has derived from an oogonium by differentiation near the time of birth
Primary spermatocytes
A diploid cell that undergoes meiosis to form four spermatocytes
-a primary spermatocye divides into two secondary spermatocytes, which in turn divide to form the spermatids
Polar bodies
Either of two small cells produced during the first and second meiotic divisions in the development of an oocyte, containing little cytoplasm and eventually degenerating
Sexual reproduction
A biological process in eukaryotes that creates a new organism by combining the genetic material of two organisms in a process that starts with meiosis
Asexual reproduction
A mode of reproduction in prokaryotes by which offspring arise form a single organism, and inherit the genes of that parent only
Fundamentally, how does mitosis differ from meiosis?
- in mitosis (asexual), two genetically identical daughter cells each develop from a single parent cell
- in meiosis (preparing for sexual reproduction), the division of a germ cell involving two fissions of the nucleus and giving rise to four gametes, or sex cellsX each possessing half the number of chromosomes of the original cell
What is meant by the terms meiosis I and meiosis II?
- Meiosis I produces two identical daughter (diploid) cells
- During meiosis II, these cells divide and produce four haploid cells
Summarize the events of meiosis I
- prophase I: homologous chromosomes link as they condense, forming tetrads; crossing over May occur
- metaphase I: microtubules move homologous chromosomes to a metaphase plate; independent assortment may occur
- anaphase I: microtubules separate homologous chromosomes (sister chromatids stay together)
- telophase I: two haploid daughter cells result from cytokinesis
Summarize the events of meiosis II
- prophase II: brief period
- metaphase II: sister chromatids line up at new metaphase plate
- anaphase II: sister chromatids separate
- telophase II: four haploid cells result
Why is meiosis I also called “reduction division”?
Because meiosis I reduced the number of chromosomes by 50% (in humans from 46 to 23, resulting in a haploid cell)
What are three key way meiosis differs from mitosis?
1) meiosis results in haploid cells while mitosis results in diploid cells
2) in meiosis homologous chromosomes line up on opposite sides of the metaphase plate, in mitosis, one sister chromosome lines up on each side
3) meiosis results in 4 different cells, mitosis results in 2 identical cells
