meiosis Flashcards
what is the definition of heredity?
where traits are transmitted from one generation to the next
what is an example of asexual reproduction in multicellular organisms?
parthenogenesis in aphids
what are the advantages of asexual reproduction?
quick
works well in a non-changing environment
what are the disadvantages of asexual reproduction?
little to no variation
less ability to adapt to a changing environment
how many chromosomes do somatic human cells have>
46
what does meiosis do to the number of chromosomes in a cell?
reduces them from diploid to haploid
why is the reduction in the number of chromosomes in a cell during meiosis important?
without it chromosome sets would increase exponentially
what has to occur for homologous chromosomes to pair?
the chromosomes have to align
what do meiotic cells do?
they induce DNA breaks to find and hold homologous chromosomes together
what enzyme induces DNA breaks, in humans?
nuclease Spo11
how are DNA breaks repaired?
using a DNA repair mechanism that uses the matching information on the intact homologous chromosome - leading to a cross-over event
what causes a cross-over event?
repairs in the DNA breaks
what is a chaisma (chiasmata)?
what forms when DNA breaks are repaired and a crossing over event occurs
what do chiasmata ensure?
that homologous chromosomes stay together until mitotic division
what are homologous chromosomes?
chromosomes containing the same gene sequences - one is derived from each parent