Window Help , 53%,0 Mon 12:43 AM Jocelyn Pabalst HW3.$18.355 (1).pdf (page 3 of

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Window Help , 53%,0 Mon 12:43 AM Jocelyn Pabalst HW3.$18.355 (1).pdf (page 3 of 4) Q Search 9. You are studying a salamander whose sex determination has been studied and determined to be the following. As in most vertebrates, males have high expression of sox9 and fgf9, while females have high expression of wnt4. 'Heat' means that the hotter it gets, the more DMRT1 is repressed. You are experimenting on embryos, trying to determine the effects of particular treatments on whether the embryos develop as males females. Do you expect primarily male or female development if you Rear the embros at a very high temperature? Inject the embryos with DMRTI protein? Inject the embryos with SOX9 protein? Inject the embryos with a chemical that blocks the activity of FGF9 protein? Inject the embros with WNT4 protein? Heat WNT4 10. In the lab, you subject salamanders to mutations and identify mutations that have is on... Sex Determin gene on an Missing (XO/2O) Extra (XXY, zzW) X chromosome 4 5 6

Explanation / Answer

Answer:

9. a. Higher temperatures induces the formation of females.

Explanation:

Genotypically, female larvae of the salamander Hynobius retardatus reared at a high temperature (28°C) during the thermosensitive period (15–30 days after hatching) develop into female adults. Thus, a nongenetic factor, such as the temperature during the thermosensitive period, overrides the chromosomal sex determination.

Generally, low temperatures induce the production of males and higher temperatures females, regardless of the genetic sex.

b. DMRT1 protein induces male formation.

Explanation:

The function of Dmrt1 in sex determination has been analyzed in species in which sex determination is influenced by environmental factors such as temperature changes.

There is a very good correlation between the temperature-dependent sex determination of turtles, alligators and salamander, and increased Dmrt1 expression at temperatures that promote male development.

c. SOX9 injection induces male formation.

Explanation:

If Sry does not intervene during a critical window in development, the cells will default to the ovarian pathway. Once Sry expression begins, other genes start to choose sides: Sox9 and Fgf9 become active only in male gonads, while Wnt4 becomes active only in female gonads.

d. Blocking Fgf9 activity would induce the formation of a female.

Explanation:

Fgf9 can induce Sox9 expression and Wnt4 and Fgf9 play a sexual tug of war. If Wnt4 wins, the gonad differentiates into an ovary. If Fgf9 wins, it turns into a testis.

So, inhibiting Fgf9 induces formation of a female via the Wnt4 pathway.

e. Injecting with Wnt4 induces the formation of a female.

Explanation:

Same as (d).

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