BMS 430 Exam 3 Questions and
Answers
What is different about birds genetic sex?
✓ ~~~XX is male
✓ XY is female
What is different about the genetic sex of fish?
✓ ~~~Can be either (XX or XY) depending on species
✓ Sometimes determined by temperature
✓ Some have the ability to switch
What gene does the Y chromosome carry which is important in sex differentiation?
✓ ~~~SRY gene
Testosterone---->DHT by
✓ ~~~enzyme 5 alpha reductase
Testosterone---->estradiol by
✓ ~~~aromatase enzyme
PDG
✓ ~~~are stem cells in the gonads
What is the SRY gene?
✓ ~~~Sex Reversal Y gene
AKA as TDF (testis determining factor)
,How does the SRY gene differentiate gonads?
✓ ~~~Turns on Sox 9, a box set of genes which influences sertoli and leydig cells to
differentiate the gonads into testis
What do the Sertoli cells produce under the influence of the SRY gene?
✓ ~~~MIF - mullarian-inhibiting factor
Causes the mullerian duct regression
What do the Leydig cells produce under the influence of the SRY gene?
✓ ~~~Testosterone
- development of Wolffian ducts
(Vas deferens, seminal vesicles, epidymis)
- DHT >> penis and scrotum development
What duct is preprogrammed to develop?
✓ ~~~Mullerian
What hormone masculinizes the brain?
✓ ~~~estradiol
What protein in females prevents estradiol from crossing the BBB and masculinizing
the brain?
✓ ~~~alpha fetoprotein produced by the liver binds and degrades estradiol
, Why can male brains be masculinized?
✓ ~~~Testosterone isn't bound by alpha fetoprotein so it crosses the BBB, attaches to
receptors and is converted into estradiol
Once masculinized, the male brain converts into what three parts?
✓ ~~~Pulse generator
Aggression center
Libido center
Describe the pulse generator
✓ ~~~- releases GnRH in pulses 90 min
- negative feedback from:
progesterone
estradiol
testosterone
DHT
Describe the aggression center
✓ ~~~estradiol causes the production of testosterone receptors
testosterone can trigger aggression
Libido center
✓ ~~~Maintained with estradiol receptors
T--->Estradiol induces male libido effects
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