Meiosis

Question 1

Nuclear division that occurs in gonads

Answer 1

Oogenesis –> ovaries

Spermatogenesis –> testes

Question 2

formation of _____ is required for reproduction

Answer 2

zygote

Question 3

how many chromosomes do human cells have?

Answer 3

46 (23 pairs)

-one maternal and one paternal set

Question 4

oogenesis steps

Answer 4

• primary oocytes (primordial and primary follicles) are stuck in prophase I
• They’re stimulated by LH to complete meiosis I just before ovulation
• After Meiosis I, there’s ONE secondary oocyte and ONE polar body
• the secondary oocyte is trapped in Metaphae II and the polar body degenerates
• At fertilization, Meiosis II is completed –> One ovum and One polar body
• The polar body degenerates

Question 5

Number of primary oocytes throughout life

Answer 5

Fetal oocytes = 7 million

At birth = 2 million

At puberty = 400,000

Question 6

about how many secondary oocytes get ovulated?

Answer 6

500

Question 7

error rates of meiosis in females

Answer 7

20% have the wrong # of chromosomes

Question 8

Spermatogenesis

Answer 8

Spermatogonium
-stem cell for more spermatogonium is diploid and mitotic –> go into meiosis at puberty

Primary spermatocytes (2n)
-meiosis I: 2 secondary spermatocytes (1n)

Secondary spermatocytes
-meiosis II: 4 spermatids (1n)

Question 9

spermatozoa anatomy

Answer 9

Head

• acrosome
• nucleus

Midpiece
-mitochondria

Tail
-flagellum

Question 10

How many sperm/how often?
How’s it regulated?
What’s the error rate?

Answer 10

puberty to life
over a trillion sperm in lifetime
-90 million sperm per day
-regulated by testosterone
-error rate of 5%

Question 11

spermatogenesis vs spermiogenesis

Answer 11

formation of sperm cells vs maturation of spermatids into sperm cells