Flashcards in Meosis Deck (6):
differences in Meiosis and Mitosis
Meiosis is sexual reproduction, mitosis is asexual reproduction. Meiosis involves crossing over and 4 distinct haploid daughter cells. Mitosis creates 2 genetically identical diploid daughter cells
what is nondisjunction and where can it occur?
Nondisjunction is when the chromosomes fail to separate properly during anaphase. This could be during meiosis I or II, or mitosis—although the scenario most commonly discussed is usually nondisjunction during meiosis I.
What are the ramifications of nondisjunction occurring?
Nondisjunction will result in an uneven number of chromosomes—either monosomy (missing chromosome) or trisomy (extra chromosome). Many such failures are fatal and only a few cases for specific chromosomes are survivable. Turner’s Syndrome is monosomy of the X chromosome. There are a few chromosomes for which trisomy is survivable, the most common one being trisomy 21—Down’s Syndrome.
when does crossing over occur and why is it important?
Crossing over occurs during prophase of meiosis I. The tetrads pair up with one another and exchange segments of DNA. In fact, crossing over happens to such an extent that two genes must be very close to one another on the chromosome to not assort independently (i.e., linkage). If crossing over did not occur we would say that all of the genes on one chromosome always demonstrated linkage.
What does meiosis yield?
Four genetically distinct haploid daughter cells