Chapter 11.5.1 (Exam 2) Meiosis Flashcards
Meiosis Leads to the Formation of Gametes
Describe meiosis.
Two nuclear divisions, but DNA is replicated only once
2n ⟶ n
Can occur only in diploid cells
Ensures each haploid product has a complete set of chromosomes
Generates genetic diversity among the products
What is meiosis I preceded by?
DNA replication in S phase
What happens in meiosis I?
Homologous chromosome pairs separate, but individual chromosomes (sister chromatids), stay together
Two haploid nuclei result, each with half of the original chromosomes (one member of each homologous pair)
What happens in prophase I?
Homologous chromosomes pair by adhering along their lengths (synapsis)
What are bivalents/tetrads in prophase I?
4 chromatids of a homologous chromosome pair form a bivalent/tetrad held together by chiasmata
What are chiasmata?
Regions of attachment that form between non-sister chromatids
What is crossing over?
Exchange of genetic material between non-sister chromatids at the chiasmata
What does crossing over result in?
Crossing over results in recombinant chromatids and increases genetic variability of the products
What are the two causes of genetic diversity in the products of meiosis I?
Crossing over and independent assortment
What is independent assortment?
Independent assortment also allows for chance combinations
It is a matter of chance how the homologous chromosomes line up in metaphase I and which ones go to which daughter cell
