Reproduction

Question 1

Interphase

Answer 1

includes G1, S, and G2; cell spends 90% of time in this phase; cells that dont divide spend all of time in G0 phase

Question 2

G1 stage-Presynthetic Gap

Answer 2

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

Question 3

S stage

Answer 3

synthesis of DNA, cell replicates so each chromosome consists of 2 identical chromatids bound at the centromere

Question 4

G2 stage: postsynthetic gap

Answer 4

cell passes through checkpoint to make sure dna was properly replicated

Question 5

M stage: Mitosis

Answer 5

consists of division of chromatids and cytokinesis-splitting of cytoplasm into two daughter cells
mitosis occurs in somatic cells

Question 6

p53

Answer 6

main protein in control of the G1/S checkpoint and the G2/M checkpoint; mutation of p53 often leads to cancer

Question 7

Prophase

Answer 7

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)

Question 8

metaphase

Answer 8

centriole pairs now at opposite ends of cell; kinetochore fibers interact with fibers of spindle to align the chromosomes at the metaphase plate

Question 9

anaphase

Answer 9

centromeres split so that each chromatid has its own centromere; sister chromatids are pulled towards opposite poles by shortening of kinetochore fibers

Question 10

telophase

Answer 10

reverse of prophase; spindle disappears, nuclear membrane reforms around each set of chromosomes, nucleoi reappear

Question 11

cytokinesis

Answer 11

separation of cytoplasm and organelles

Question 12

asters

Answer 12

microtubules that anchor centrioles to cell membrane

Question 13

Meiosis I

Answer 13

homologous chromosomes separated generating haploid daughter cells; reductional division

Question 14

Meiosis II

Answer 14

equational division- separation of sister chromatids, like in mitosis

Question 15

Prophase I

Answer 15

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

Question 16

metaphase I

Answer 16

homologous pairs align at metaphase plate and each pair attaches to a separate spindle fiber by its kinetochore

Question 17

anaphase I

Answer 17

homologous pairs separate and are pulled to opposite poles (disjunction)

Question 18

telophase I

Answer 18

nuclear membrane forms around each new nucleus, cells are now haploid; cell divides into two daughter cells by cytokinesis

Question 19

Leydig cells

Answer 19

production of testosterone and other androgens

Question 20

seminiferous tubules

Answer 20

located in testes, produce sperm (spermatogenesis) which are nourished by sertoli cells

Question 21

pathway of sperm through the male tract

Answer 21

SEVE(n) UP: seminiferous tubules–epididymis–vas deferens–ejaculatory duct–urethra–penis

Question 22

spermatogenesis

Answer 22

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

Question 23

structure of mature sperm

Answer 23

head contains genetic material, midpiece filled with mitochondria and generates energy to swim, and a flagellum for movement

Question 24

Oogenesis

Answer 24

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

Question 25

FSH- males

Answer 25

stimulates Sertoli cells to produce mature sperm

Question 26

LH-males

Answer 26

causes production of testosterone

Question 27

estrogens

Answer 27

secreted in response to FSH; leads to development of female reproductive structures in an embryo and thickening of uterus lining in adults

Question 28

progesterone

Answer 28

secreted by corpus luteum, the follicle that remains after ovulation in response to LH, involved in the maintenance of the endometrium

Question 29

follicular phase of menstrual cycle

Answer 29

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

Question 30

ovulation

Answer 30

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

Question 31

luteal phase

Answer 31

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

Question 32

menstruation

Answer 32

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

Question 33

pregnancy

Answer 33

after fertilization, zygote will develop into blastocyst that will secrete human chorionic gonadotropin (hCG), an analogue of LH which will maintain the uterine lining

Question 34

menopause

Answer 34

occurs due to ovaries becoming less sensitive to FSH and LH