Lecture 6 Flashcards
define Autosome
Chromosomes common to both sexes; one from each parent in each parent in each diploid nucleus
What is a cohesin complex?
the structure that holds sister chromatids together
what occurs in the S phase of the cell cycle?
DNA replication (S for synthesis of new DNA)
Define homolog
copies of the same gene (you should end up with one from each parent)
sister chromatids are identical copies of homologs
compare and contrast the cells at the end of meiosis I and Mitosis
Meiosis I cell’s homologs are separated which creates a haploid cell
Mitosis cells have sister chromatids separated which creates diploid, genetically identical cells
Compare and contrast cells at the end of meiosis II to mitotic cells
4 haploid daughter cells are created by the end of meiosis II
Mitotic cells create diploid daughter cells that are genetically identical
What are the 5 phases of prophase I?
Leptotene
Zygotene
Pachytene
Diplotene
Diakinesis
Define the Lepotene phase of Prophase I
Homologs begin to condense/pair
Define the Zygotene phase of Prophase I
Homologs pair and synaptonemal complexes form in order to keep the homologs tightly paired
Define the Pachytene phase of Prophase I
Synapsis is complete and crossing over begins to occur
Define the Diplotene phase of Prophase I
Synaptonemal complex begins to break down so that the homologs can eventually be pulled apart
○ Homologs are still tethered together by the Chiasmata (the “X” formed by crossing over)
Define the Diakinesis phase of Prophase I
the chromatids reach maximum condensation (to protect DNA from damage) and the homologs are pulled apart
○ This begins the transition into metaphase
Where do primary oocytes arrest during embryonic development?
Meiosis I
In order to generate enough gamete egg cells for an entire lifetime, what type of cell division occurs in females?
mitotic division prior to meiotic division
until fertilization occurs, at what stage to secondary oocytes arrest?
Metaphase II
Describe oocytes compared to sperm. how did they get this way?
they are much larger and complex; polar bodies formed during oogenesis allow this increased cytoplasm
at what stages of oogenesis do polar bodies form?
the completion of meiosis I and the completion of Meiosis II
where do primordial germ cells (PGC’s) migrate in males? what type of cell division occurs there?
the testis ; mitotic division
where does crossing over during the formation of sperm cells occur?
prophase I
at one point in spermatogenesis do sperm cells have just one sex cell?
the completion of Meiosis I
how many spermatids are present at the end of Meiosis II? are they haploid or diploid?
4 ; haploid
describe the path ,along anatomical chambers, of spermatids during their development.
testis ; lumen of seminiferous tubules ; epididymis (where they fully mature)
What do Sertoli cells do?
they maintain close contact with sperm cells throughout their maturation process.
