Reproduction Flashcards
Interphase
includes G1, S, and G2; cell spends 90% of time in this phase; cells that dont divide spend all of time in G0 phase
G1 stage-Presynthetic Gap
cells create organelles for energy and protein production, and increase in size; contains checkpoint in order to make sure cell has adequate resources for division
S stage
synthesis of DNA, cell replicates so each chromosome consists of 2 identical chromatids bound at the centromere
G2 stage: postsynthetic gap
cell passes through checkpoint to make sure dna was properly replicated
M stage: Mitosis
consists of division of chromatids and cytokinesis-splitting of cytoplasm into two daughter cells
mitosis occurs in somatic cells
p53
main protein in control of the G1/S checkpoint and the G2/M checkpoint; mutation of p53 often leads to cancer
Prophase
chromatin condenses to form chromosomes; centriole pairs separate and move towards opposite poles; centrioles begin to form spindle fibers; nuclear membrane dissolves, allowing spindle fibers to contact the chromosomes; kinetochores appear at centrosome (attachment points for spindle)
metaphase
centriole pairs now at opposite ends of cell; kinetochore fibers interact with fibers of spindle to align the chromosomes at the metaphase plate
anaphase
centromeres split so that each chromatid has its own centromere; sister chromatids are pulled towards opposite poles by shortening of kinetochore fibers
telophase
reverse of prophase; spindle disappears, nuclear membrane reforms around each set of chromosomes, nucleoi reappear
cytokinesis
separation of cytoplasm and organelles
asters
microtubules that anchor centrioles to cell membrane
Meiosis I
homologous chromosomes separated generating haploid daughter cells; reductional division
Meiosis II
equational division- separation of sister chromatids, like in mitosis
Prophase I
chromatin condenses into chromosomes, spindle forms, nuclear membrane disappears; chromosomes intertwine in synapsis; tetrad forms with 4 chromatids and crossing over occurs when chromatids break at point of contact (chiasma) and exchange equivalent regions of DNA
metaphase I
homologous pairs align at metaphase plate and each pair attaches to a separate spindle fiber by its kinetochore
anaphase I
homologous pairs separate and are pulled to opposite poles (disjunction)
telophase I
nuclear membrane forms around each new nucleus, cells are now haploid; cell divides into two daughter cells by cytokinesis
Leydig cells
production of testosterone and other androgens
seminiferous tubules
located in testes, produce sperm (spermatogenesis) which are nourished by sertoli cells
pathway of sperm through the male tract
SEVE(n) UP: seminiferous tubules–epididymis–vas deferens–ejaculatory duct–urethra–penis
spermatogenesis
four haploid sperm produced from a spermatogonium
after S stage, germ cells called primary spermatocytes; after meiosis I, secondary spermatocytes; after meiosis II, spermatids; after maturation, spermatozoa
structure of mature sperm
head contains genetic material, midpiece filled with mitochondria and generates energy to swim, and a flagellum for movement
Oogenesis
by birth, all of oogenia have already undergone dna replication and formed primary oocytes (2n), arrested in prophase I; one oocyte released per month during menses and completes meiosis I to produce secondary oocyte and a polar body due to unequal cytoplasm division; secondary oocyte arrested in metaphase II unless fertilization occurs, when sperm penetrates layers of oocyte; meiosis II divides into mature ovum and another polar body
FSH- males
stimulates Sertoli cells to produce mature sperm
LH-males
causes production of testosterone
estrogens
secreted in response to FSH; leads to development of female reproductive structures in an embryo and thickening of uterus lining in adults
progesterone
secreted by corpus luteum, the follicle that remains after ovulation in response to LH, involved in the maintenance of the endometrium
follicular phase of menstrual cycle
begins when menstrual flow begins, sheds uterine lining; GnRH secreted in response to decreased E2 and P, which then causes increase in FSH and LH, which cause follicles to develop that produce E2 (provide neg. feedback); E2 helps to regrow endometrial lining
ovulation
E2 reaches threshold that causes it to have positive feedback on GnRH, producing a LH and FSH spike triggering the release of the ovum from the ovary
luteal phase
after ovulation, LH causes ruptured follicle to form corpus luteum, which secretes P (maintains uterine lining for implantation); high P causes neg. feedback on GnRH, preventing further ovulation
menstruation
if implantation doesnt occur, uterine lining is sloughed off due to corpus luteum losing LH stimulation; loss of high levels of E and P remove neg. feedback on GnRH
pregnancy
after fertilization, zygote will develop into blastocyst that will secrete human chorionic gonadotropin (hCG), an analogue of LH which will maintain the uterine lining
menopause
occurs due to ovaries becoming less sensitive to FSH and LH
