Physiology Reproduction A

Front 1

1. What is the evidence that the y chromosome is involved in testes formation?

Back 1

a. XO humans with ____Turner’s____are females and __without___ testes.

b. Despite having two X chromosomes, XXy humans with ___Klinefelter’s___are males with __testes____.

c. Absence of portion of y chromosome sometimes results in __female_____ phenotype in humans. Humans with a portion of y chromosome missing develop a vestigial (poorly developed) ____streak gonad______ similar to XO humans with Turner's Syndrome.

d. Many XX human males with testes contain a piece of the _Y__ chromosome.

Front 2

2. What is the evidence that the X chromosome is necessary for sexual development?

Back 2

X chromosome is necessary for development of ovary, testes, oogenesis and spermatogenesis. The X chromosome has much more genetic information than the y, however one of two X chromosomes in the female is completely or partially inactivated in autosomal cells during embryonic development.

Front 3

3. T or F: germ cells are necessary for testes formation and function?

Back 3

False: but oocytes (primordial follicles) are required for survival and endocrine function of follicles

Front 4

4. If a male or female fetus is castrated, the internal genitalia of a male or female develops.

Back 4

Female genitalia will develop (mullerian ducts)

If a male fetus is castrated then added testosterone , the internal genitalia is?

Both wolffian and mullerian ducts

If a male fetus is castrated then added testosterone anagonist , the internal genitalia is?

Both wolffian and mullerian ducts are blocked

Front 5

5. The genital folds elongate and fuse to form the ovary, seminiferous tubules, or the shaft of the penis and labia minora.

Back 5

the shaft of the penis and labia minora

Front 6

6. Discuss the evidence that the male produces two hormones involved in development of male genitalia?

Back 6

a. If a male embryo is castrated, _____Mullerian Ducts____ develop.

b. The addition of_Testosterone___ into a castrated male embryo results in development of both Wolffian and Mullerian ducts.

c. The addition of a testosterone __Antagonist___ into an intact male embryo blocks development of both Wolffian and Mullerian ducts.

The aforementioned experiments indicate that development of the Wolffian duct system is dependent on production of _ ___tesosterone___ by the testes and that the testes also produce a factor that ___androgens__ Mullerian duct development. The factor that blocks Mullerian duct formation is called the Mullerian Inhibiting Factor or Anti-Mullerian Hormone.

Front 7

7. What are the two hormones produced by the male that promote development of the male reproductive system?

Back 7

The aforementioned experiments indicate that development of the Wolffian duct system is dependent on production of _testosterone_ by the testes and that the testes also produce a factor that __androgens_ Mullerian duct development.

The factor that blocks Mullerian duct formation is called the Mullerian Inhibiting Factor or Anti-Mullerian Hormone.

Front 8

8. Give examples of how steroid enzymes may be involved in sexual development?

Back 8

On day 17, testosterone synthesis begins (Fig 5, top panel) and 3β-hydroxysteroid dehydrogenase (3BHSD; converts androstenediol to testosterone and is rate-limiting enzyme for synthesis of testosterone, see Fig 5, lower panel) activity is detectable in males. In contrast, testosterone production is low in females, although estrogen production is high [11].

3. Two differences exist in the steroid enzymes between the ovary and testis in neonatal rabbits:
a. 50 times more 3BHSD in the fetal rabbit testis compared with the ovary (Fig 5, lower panel, [11]).
b. Fetal ovary has much larger amounts of an enzyme called aromatase than fetal testes. Aromatase converts testosterone (T) into estradiol

Front 9

9. What is the evidence that the brain or the central nervous system (brain) may be altered during sexual development by hormones? Which hormones may be involved in alteration of the central nervous system during sexual development?

Back 9

Unknown **find answer**

Front 10

10. What are the implications and importance of the aromatization and protection hypotheses relative to sexual development?

Back 10

The ___aromatase__Hypothesis: during embryo development conversion of testosterone to estradiol by the ____Aromatase__ enzyme located in the brain of embryos has an important role in stimulating male behavior in adults. Thus, estradiol rather than testosterone may be important for “triggering” male behavior during embryonic development.
Evidence supporting the aromatization hypothesis was generated by injecting pregnant rats with estradiol, estradiol antagonists, testosterone, or DHT and examining effects of these factors on brain development and reproductive behavior of the female offspring. The results of these studies follow:
A) Female embryos exposed to either __testosterone__ or ___estradiol___ during gestation had similar brain anatomies after birth.
B) Female embryos exposed to estradiol or
testosterone during gestation did not ___Ovutalate___ or have normal estrous cycles as adults. Thus, exposure of female embryos to estradiol or testosterone results in development of “masculine” behavior after birth.