15.1 Flashcards
sexual reproduction transmits genetic information through cycles of meiosis and fertilzation
- germ-line cells carry out meiosis to produce haploid gametes
- haploid gametes fuse to produce diploid zygote
- zygote inherits genetic material from 2 parents
- mitosis
meisos is similar to mitosis
both use microtubule based spindle machine
both segregate condensed DNA molcuels to 2 daughter cells
both include prophase, metaphase, anapase, and telophase
meiosis has ket feautres that disitnguish if from mitosis
2 rounds of division (meiosis 1 and 2)
only 1 round of DNA replication
synapsis
crossing over
synapsis
association between homologus chromosome pairs in meiosis 1
-occurs during early prophase 1
-homologous chromosomes become closely associated
-involves formation of synaptonemal complex
also called a tetrad or bivalent
crossing over
homologues exchange DNA segments
-allows the homologues to exchange chromosomal material
-genetic recombination between nonsister chromatids
-alleles of genes that were formerly on separate homologues can now be found on the homologue
-sites of crossing over are termed chiasmate
-contact maintained until anaphase 1
meiosis 2
meiosis 2 occurs after an interval of variable length
-DNA replication is suppressed between meiosis 1 and meiosis 2
-resembled a mitotic division=> separation of sister chromatids