Gonad Development

Question 1

What factors promote the differentiation to testis?

Answer 1

• chromosome Y: sry gene ▶️ TDF ▶️ testis
• leydig cells ▶️ testosterone
• sertoli cells ▶️Müllerian inhibitory factor (MIF)▶️suppresses development of paramesonephric (Müllerian) ducts (female internal structures)
• DHT: external genitalia

Question 2

What is the difference between meiosis I and II, for what is that process?

Answer 2

• meiosis I: synapsis (pairing 46 homologous chromosomes), crossing over (exchange segments of DNA), disjunction (separation of chromosomes without centromere splitting)
• meiosis II: no synapsis, no crossing over, disjunction with splitting (reduction 2n to 1n)

Question 3

How many arrest occur in the oogenesis since fetal live until ovulation?

Answer 3

• First, primary oocyte in profase (dyplotene) MI in fetal life until puberty.
• Second, after puberty each month a secondary oocyte is produced by completing MI and initiate MII, and arrested at metaphase, in this stage is ovulated.

Question 4

Where come from the primordial germ cells to the gonad development? Where do they migrate at week 4?

Answer 4

• from the yolk sac

- indifferent gonad at Urogenital ridge (intermediate mesoderm)

Question 5

What is the correctly number of chromosomes and the complement of DNA of a secondary spermatocyte? Why?

Answer 5

• 23, 2n
• secondary spermatocyte is formed at the end of meiosis I and has a haploid number of chromosomes and a 2n complement of DNA