36.2 - Oogenesis

Question 1

-Ovaries

-Cyclical (has a limited number of eggs / mental cycle)

-Lose stem cells (develop something else)

-One Egg

-Large Eggs nutrients for embryonic development

-Two meiotic divisions (but one makes junk / polar body)

-Several months

-400,000 primary oocytes at birth

-Pregnancy hard on mammals

-Positive Feedback ALLOWS HORMONE FLUCTUATION

-1 Egg per primary oocyte

-Females mammals generally produce fewer because risk and cost of pregnancy

Answer 1

Oogenesis
(Slide 3)

Question 2

Oogenesis starts

Answer 2

Before a female is born (400,000 primary oocytes)
The first steps occur in the fetal ovary

Question 3

Step 1 (In embryo) (2n)

Answer 3

Primordial germ cells divide, making the oogonia (stem cell)

Question 4

Step 2 (in embryo) (2n)

Answer 4

Oogonuim divides by mitosis to produce oogonium and primary oocyte (no more stem cells ovary)

Question 5

Step 3 (in embryo) (2n) Stays Until Puberty

Answer 5

Primary oocyte initiates Meosis 1 but arrests at prophase 1 until puberty

Question 6

Step 4 - triggered by what? (1n)

Answer 6

The primary oocyte is stimulated to resume meiosis and complete meiosis 1

Creates two daughter cells
-Secondary oocyte
-Polar body (used for genetic waste)

Question 7

Step 5 (1n) Rest for few days

Answer 7

Secondary oocyte arrest in metaphase 2 (few days) developing in the ovarian follicle accumulating protein / mRNA from other cells

Question 8

Step 6 (1n)

Answer 8

Ovulation releases the oocyte from the ovary to enter the oviduct, along with sperm (male)

Question 9

Step 7 (1n) END

Answer 9

Fertilization occurs in the oviduct (complete of meiosis 2)
-Secondary oocyte divides to create a fertilized egg and a polar body
-ONE EGG