Gametogenesis and Reproduction

Question 1

Precursors to germ cells and originate in the yolk sac endoderm. They migrate to the genital ridges by ameboid movement

Answer 1

Primordial Germ Cells (PGCs)

Question 2

Originate as genital ridges near the developing hindgut in early embryonic development

Answer 2

Gonads

Question 3

Used to identify the PGCs early in the fertilized egg

Answer 3

Germ Plasm

Question 4

Directs the development of testes in mammals

Answer 4

SRY gene

Question 5

Gene that drives Sertoli Cell formation

Answer 5

SOX9

Question 6

The hormones produced by testes which masculinizes the fetus

Answer 6

Testosterone and Dihydrotestosterone

Question 7

Enzymatically converted to in the brain from testosterone, it influences male typical behavior in many mammals and birds

Answer 7

Estrogen

Question 8

How a high temperature determines the sex of specific animals

Answer 8

• Many lizards and alligators: Higher percentage of males
• Leopard geckos, snapping turtles, crocodiles: Lower percentage of males
• Many turtles: Parabolic percentage of males

Question 9

Without SRY, the gonad becomes an ovary by default guided by these genes on the X chromosome

Answer 9

WNT4 and DAX1

Question 10

Likely reason why female brain development is protected from estrogen’s masculinizing effects

Answer 10

Low brain estrogen receptor levels in humans and primates

Question 11

Occurs in the seminiferous tubules, gives rise to mature sperm

Answer 11

Spermatogenesis

Question 12

Nourishes and supports spermatogenesis

Answer 12

Sertoli Cells

Question 13

Spermatozoa Structure

Answer 13

• Head: Contains the condensed nucleus and an acrosome, which releases enzymes like hyaluronidase to penetrate the egg
• Middle Piece: Packed with mitochondria for energy
• Tail

Question 14

First stage of spermatogenesis

Answer 14

Spermatogonia: Diploid germ cells at the periphery of the seminiferous tubules divide by mitosis

Question 15

Second stage of spermatogenesis

Answer 15

Primary Spermatocytes: Selected spermatogonia grow and move closer to the tubule lumen, undergoing the first meiotic division to form two haploid secondary spermatocytes

Question 16

Third stage of spermatogenesis

Answer 16

Secondary Spermatocytes: Undergo the second meiotic division to produce four haploid spermatids per primary spermatocyte

Question 17

Fourth step of spermatogenesis

Answer 17

Spermatid: Transform into spermatozoa (mature sperm) without further development

Question 18

Occurs in the ovary, gives rise to ovum

Answer 18

Oogenesis

Question 19

First stage of oogenesis

Answer 19

Oogonia: Diploid cells that divide by mitosis and grow into primary oocytes

Question 20

Second stage of oogenesis

Answer 20

Primary oocyte: Undergoes meiosis, which is arrested at prophase 1 until puberty in most vertebrates

Question 21

Third stage of oogenesis

Answer 21

Secondary oocyte and polar bodies: At ovulation, meiosis 1 is completed, producing a large secondary oocyte and a small nonfunctional first polar body

Question 22

Fourth stage of oogenesis

Answer 22

Ovum: If fertilized, the secondary oocyte completes meiosis II forming a haploid ovum and a second polar body

Question 23

Reproductive pattern where eggs are laid outside the body to develop. Fertilization can be either internal or external

Answer 23

Oviparity

Question 24

Reproductive pattern where fertilized eggs develop inside the oviduct or uterus nourished by yolk stored in the egg. Fertilization is internal

Answer 24

Ovoviviparity

Question 25

Reproductive pattern where the fertilized eggs develop inside the oviduct or uterus with nourishment directly from the mother. Fertilization is internal and the young are born at a more advanced developmental stage

Answer 25

Viviparity

Question 26

Sperm Pathway

Answer 26

- Seminiferous tubules - Vas efferens - Epididymis - Vas deferens - Ejaculatory duct - Urethra

Question 27

Function of secreted fluids of the male mammal accessory glands

Answer 27

- Nourish sperm - Lubricate the female reproductive tract - Neutralize vaginal acidity for prolonged sperm viability

Question 28

Specialized lining in the uterus

Answer 28

Endometrium

Question 29

Cycle of endocrine events that orchestrate reproduction in vertebrates

Answer 29

- Hypothalamus (Gonadotropin-releasing Hormone)) - Pituitary (Luteinizing Hormone for male, Follicle-Stimulating Hormone) for female) - Testis for male (Testosterone)/Ovary for female (Estrogen and Progesterone)

Question 30

Reproductive cycle found in most mammals where females are only receptive to males during specific periods of heat

Answer 30

Estrous Cycle

Question 31

Reproductive cycle where females may be receptive to males throughout the cycle, with increased receptivity around ovulation

Answer 31

Menstrual Cycle

Question 32

End of the menstrual cycle

Answer 32

Menstruation (Shedding of endometrium)

Question 33

Functions of Estrogen

Answer 33

- Development of female sex structures (Oviduct, uterus, vagina) - Stimulating reproductive activity - Controlling secondary sex characteristics (Skin color, bone development, body size, mammary glands in mammals)

Question 34

Functions of Testosterone

Answer 34

- Development of male sex structures (Penis, sperm ducts, glands) - Secondary male sex characteristics (Bone and muscle growth, voice quality, male coloration) - Male sexual behavior

Question 35

Secreted by both ovaries and testes, it is a peptide hormone that regulates FSH secretion through negative feedback

Answer 35

Inhibin

Question 36

Phase of the menstrual cycle where the endometrium degenerates and sheds, resulting in blood and tissue discharge

Answer 36

Menstrual Phase

Question 37

Phase in the menstrual cycle that begins with the rising levels of FSH and LH, causing ovarian follicles to grow and secrete estrogen. Estrogen thickens the uterine lining and enlarges the uterine glands (Proliferative phase)

Answer 37

Follicular Phase

Question 38

The dominant follicle that isn't degenerated by Day 10

Answer 38

Graafian Follicle

Question 39

Secreted by the Graafian Follicle to decrease FSH levels

Answer 39

Estrogen and Inhibin

Question 40

Phase in the menstrual cycle that has high levels of estrogen which trigger positive feedback on the hypothalamus, leading to a surge in GnRH and LH. The LH surge causes the rupture of the Graafian Follicle and releases an oocyte, viable for 12 hours

Answer 40

Ovulation

Question 41

Phase in the menstrual cycle where the ruptured follicle transforms into the corpus luteum, which secretes progesterone in response to LH. Progesterone prepares the uterus for gestation (Secretory phase)

Answer 41

Luteal Phase

Question 42

Cause and result of the degeneration of the corpus luteum

Answer 42

No fertilization causes degeneration, leading to a decrease in progesterone and estrogen

Question 43

Three tissue layers formed by developing embryo

Answer 43

- Amnion - Chorion - Embryo Proper

Question 44

Secreted by the chorion which stimulates to corpus luteum to release estrogen and progesterone

Answer 44

Human Chorionic Gonadotropin (hCG)

Question 45

Hormones that prepare the mammary glands for milk secretion

Answer 45

Prolactin (PRL) and Human Placental Lactogen (hPL)

Question 46

Hormone secreted by the placenta that increases the flexibility of the pubic symphysis and dilates the cervix in preparation for delivery

Answer 46

Relaxin

Question 47

Three stages of birth

Answer 47

- Dilation (Cervix enlarges) - Expulsion (Fetus is delivered) - Placental Delivery (Expulsion of the placenta)

Question 48

Hormones that stimulate uterine contractions

Answer 48

Prostaglandins and Oxytocin

Question 49

Hormones released triggered by infant sucking on mammary glands

Answer 49

Oxytocin and Prolactin

Question 50

Type of human twins that come from one zygote and are genetically identical, always of the same sex

Answer 50

Identical (Monozygotic) Twins

Question 51

Type of human twins that come from two separate zygotes and are genetically no more alike than other siblings

Answer 51

Fraternal (Dizygotic) Twins