Meiosis from Rich Notes Flashcards
How many pairs of autosomes do humans have? How many pairs of sex chromosomes do humans have? What types of sex chromosomes do females have? Males? (Normally)
22; 1; XX; XY
What are two ways in which meiosis creates genetic diversity?
random assortment of chromosomes and recombination
What letter is used to designate the number of haploid sets of chromosomes in a cell? What letter is used to designate the content of DNA in a cell?
N; C
How much DNA content do each of the following have? A diploid somatic cell in G1 A diploid somatic cell in G2 A gamete in prophase of meiosis Gametes after Meiosis I? II?
2C 4C (finished DNA replication in S phase) 4C 2C 1C
How many sets of haploid chromosomes do each of the following have?
gamete after Meiosis I
gamete after Meiosis II
1N
1N
What is the term for when a cell has an abnormal number of chromosomes that are not complete haploid sets? What is it called when an extra copy of a single chromosome is present? What is it called when there is a loss of one copy of a single chromosome?
aneuploid; trisomy; monosomy
Where do close pairing and recombination take place?
synaptonemal comlex
What is the process that takes place in the synaptonemal complex? (Something binds, then something binds, etc.)
proteins deposited on long axis of chromosome forming axial elements, DNA extends in loops, other proteins deposited in between axial ele., axial ele. now become lateral ele., lateral ele. connected by transverse filaments, these overlap to form central element
What is located at intervals along the synaptonemal complex? They contain enzymes that mediate the recombination between non-sister chromatids of homologous chromosomes.
recombination nodules
What are the steps of recombination?
Spo11 makes ds break in 1 chromatidof 1 of the paired homologs, end of DNA digested in 5’ to 3’ direction by nuclease, tail invades adjacent chromatid of other paired homolog, break in DNA repaired by new DNA synthesis using homologous chromatid as template- forms crossover, resolvase releases the crossover, few crossovers remain as chiasmata until separation; ready to separate at anaphase
What are the stages of Meiotic Prophase I?
Leptotene, Zygotene, Pachytene, Diplotene, and Diakenesis
Leprous Zebras Pack Diplomatic Diaries.
Dumb, but it works.
During which stage of prophase Ido the chromosomes condense, homologous chromosomes begin to pair, and axial elements of the synaptonemal complex form?
leptotene
During what stage of Prophase I do the synapsis of chromosomes begins and the central and lateral elements of the synaptonemal complex begin to form?
zygotene
During which stage of Prophase I is synapsis and recombination both complete?
pachytene
During what stage of Prophase I does the synaptonemal complex disassemble and oocytes become arrested until stimulated by ovulation? (fun stuff)
diplotene
During which stage of Prophase I are the chromosomes fully condensed and ready for metaphase? This stage is homologous to prometaphase in mitosis.
diakenesis
What aligns on the metaphase plate in Metaphase I?
homologous chromosomes
What are attached to the same spindle pole in Metaphase I?
both sister chromatids of the same chromosome
During metaphase I, what holds the homologs together, and what holds the sister chromatids on a chromosome together?
chiasmata; cohesin at the centromere
What separates in anaphase I? What else happens?
homologous chromosomes; remaining cohesin along arms is removed, chiasmata disassembled
What does NOT occur in telophase I and cytokinesis of meiosis, which is different than what occurs in telophase of mitosis? Why?
the nuclear envelope does not reform and the chromosomes do not decondense; MPF activity remains high
What phases are basically skipped between end of Meiosis I and start of Meiosis II?
interphase and prophase II
Do the daughter gametes from Meiosis I undergo DNA replication before they enter Meiosis II?
No.
What attaches to opposite poles of the spindle during metaphase II?
kinetochores of sister chromatids
