6.3 - Meoisis Flashcards
What is meiosis? How many divisions does it involve? What do the gametes contain?
Meiosis is a type of cell division that produces four genetically diverse haploid cells (gametes), each containing half the chromosome number of the parent cell.
What are the two divisions involved in meiosis?
Meiosis I: The reduction division, where homologous chromosomes are separated into two haploid cells.
Meiosis II: The second division, similar to mitosis, where chromatids are separated, resulting in four haploid cells.
What are homologous chromosomes?
Homologous chromosomes are pairs of chromosomes, one inherited from each parent, that have the same genes in the same loci but may carry different alleles for those genes. They are found in diploid cells.
What are alleles?
Alleles are different versions of a gene that can exist at the same locus on homologous chromosomes. For example, a gene for eye color may have the alleles for blue eyes or brown eyes.
What happens during prophase I of meiosis?
HINT: Crazy New Hares Cross Borders
Crazy = Chromosomes condense and become visible.
New = Nuclear envelope dissolves, and spindle fibers form.
Hares = Homologous chromosomes pair up, forming bivalents.
Cross = Crossing over occurs.
Borders = Bivalents exchange DNA, leading to genetic variation.
What occurs during metaphase I of meiosis? What is this known as and what does it contribute to?
During metaphase I, homologous chromosome pairs align randomly along the metaphase plate. This random orientation is called independent assortment, contributing to genetic variation.
What happens during anaphase I of meiosis?
During anaphase I, homologous chromosomes are pulled to opposite poles, while the chromatids remain joined at the centromere. Crossing over may result in the exchange of genetic material between chromatids at points called chiasmata.
What may crossing over, during Anaphase 1, result in?
Crossing over may result in the exchange of genetic material between chromatids at points called chiasmata.
What happens during telophase I of meiosis?
During telophase I, the chromosomes gather at opposite poles, the nuclear envelope reforms, and the cell undergoes cytokinesis, resulting in two haploid daughter cells.
What happens during prophase II of meiosis?
During prophase II, the chromosomes condense again, the nuclear envelope dissolves, and spindle fibers form. The chromosomes, which still consist of two chromatids, become visible.
What occurs during metaphase II of meiosis?
In metaphase II, individual chromosomes align along the metaphase plate. Since chromatids are no longer identical due to crossing over, independent assortment occurs again, contributing to genetic diversity.
What happens during anaphase II of meiosis?
During anaphase II, the centromeres divide, and the chromatids of the individual chromosomes are pulled toward opposite poles, just like in mitosis.
What happens during telophase II of meiosis?
During telophase II, the chromatids gather at opposite poles, the nuclear envelope reforms, and cytokinesis occurs. This results in four haploid daughter cells, each genetically different from one another and the parent cell.
How does crossing over contribute to genetic variation?
During prophase I of meiosis, homologous chromosomes exchange genetic material at points called chiasmata, forming recombinant chromatids. This process creates new combinations of alleles, increasing genetic variation.
How does independent assortment lead to genetic variation?
Independent assortment occurs during metaphase I, where the orientation of homologous chromosome pairs is random. This results in different combinations of chromosomes in the daughter cells, further increasing genetic variation.
