All Things Genetics Flashcards
What is crossing over and when does it occur?
The exchange of genetic material between chromosomes during meiosis - occurs in prophase I.
What is independent assortment and when does it occur?
Random orientation of each pair as they line up along the metaphase plate - occurs in metaphase II.
What is spermiogenesis?
Process by which spermatic develop into mature spermatozoa as they pass through the rete testis and epididymis.
What is a spermatogenic cycle?
Time taken for reappearance of the same stage of spermatogenesis in a given section of tubule. (16 days in humans).
What is a spermatogenic wave?
The distance between sperm that are at the same stage of spermatogenesis.
What is sperm capacitation?
The final maturation of sperm that doesn’t occur until sperm are in the female genital tract and have bound to the zona pellucida and the acrosome reaction is initiated.
Describe the points where oogenesis halts.
Meiosis I starts in the embryo but arrests in prophase I as a primary oocyte surrounded by follicular cells - this is the primordial follicle.
Meiosis I completes when stimulated by LH surge to form a secondary oocyte.
Secondary oocyte starts meiosis II but arrests in metaphase II until a few hours before ovulation.
Meiosis II only completes if the oocyte is fertilised.
What happens to the corpus luteum if no fertilisation occurs?
Corpus luteum degenerates after 14 days and becomes the corpus albicans, progesterone production decreases, causing bleeding.
What happens to the corpus luteum if fertilisation occurs?
Degeneration of corpus luteum is prevented by hcg (secreted by embryo). Corpus luteum continues to grow and secrete oestrogen and progesterone, becomes the corpus luteum graviditatis.
