Meiosis and sexual life cycles
1) Asexual reproduction is where a single parent is
the sole parent that passes copies of its genetic information on to the next
generation. Sexual reproduction is where two individuals of the same species
contribute genes to their offspring. This results in greater genetic variation
then asexual reproduction.
Links:
For a complete list of simmilarities and differences between asexual and sexual reproduction click here
For examples of each type of reproduction click here
For a complete list of simmilarities and differences between asexual and sexual reproduction click here
For examples of each type of reproduction click here
2) Meiosis is the type of cell division that reduces the number of sets of chromosomes from two to one. In doing this, each gamete cell has half the genetic information it needs to survive and when it meets a gamete from the other parent in fertilization the newly formed organism is genetically different then its parents.
Links:
For some interesting facts about meiosis click here
For more specifics on meiosis and fertilization click here
For some interesting facts about meiosis click here
For more specifics on meiosis and fertilization click here
3) Homologous chromosomes are important to meiosis because they both carry a gene that controls the same inherited characteristics. This is important because during crossing over, the genes are located in the same place so therefore they can cross over evenly without much room for error.
Links:
For an animation depicting homologous chromosomes during crossing over click here
For an article about chromosomes and the specifics of crossing over click here
For an animation depicting homologous chromosomes during crossing over click here
For an article about chromosomes and the specifics of crossing over click here
4) The chromosome number is reduced from diploid to haploid in meiosis by in meiosis I, the homologous chromosomes are joined together along their length and then crossing over occurs which transfers parts of DNA from one homologous chromosome to the other. After this, the newly varied genetic information prepares to divide into two cells and in doing this, the homologous chromosomes move to opposite poles of the cell and then cytokinesis occurs. In each daughter cell, there are a haploid number of chromosomes. In meiosis II, the sister chromatids are then separated into four different daughter cells.
Links:
To learn more about the specifics of meiosis and how the chromosome numbers are depleted click here
For a complete description of the stages of meiosis I click here
To learn more about the specifics of meiosis and how the chromosome numbers are depleted click here
For a complete description of the stages of meiosis I click here
5) There are three important events that occur in meiosis but not in mitosis. Synapsis and crossing over only occur in meiosis and not mitosis. At metaphase I, paired homologous chromosomes are positioned on the metaphase plate, rather than individual replicated chromosomes as in mitosis. And third, at anaphase I duplicated chromosomes of each homologous pair separate but the sister chromatids of each duplicated chromosomes stay attached. In mitosis however, the chromatids separate.
Links:
For a complete list of similarities and differences between meiosis and mitosis click here
For an animation comparing meiosis and mitosis click here
For a complete list of similarities and differences between meiosis and mitosis click here
For an animation comparing meiosis and mitosis click here
6) Crossing over, independent assortment, and random fertilization all result in genetic diversity. In crossing over, genetic material on homologous chromosomes between non-sister chromatids occurs. In doing so, there is genetic variation on all chromosomes that wasn’t there before. In independent assortment of chromosomes, the chromosomes can line up on the metaphase plate in any combination, with any homologous pair facing either pole. This means that there is a 50% chance that are particular daughter cell will get a maternal or paternal chromosomes for that pair. In random fertilization, each egg and sperm are different, as a result of independent assortment and crossing over, making each egg and sperm unique.