NATS 1675 LNs 14

What is chromosomal sex determination?

• The genetic/biological sex of the body is determined by DNA

• The XY chromosome sex-determination system identifies the genetic/biological sex of the body

Gametes

All cells except gametes have a total of 46 chromosomes (22 pairs of autosomes & 1 pair of sex chromosomes).

Gametes are sperm and egg cells.

When does sexual differentiation begin?

During fetal development at weeks 5-6.

Embryonic males and females are genetically different but they are morphologically identical

The early fetus is sexually undifferentiated and contains two sets of ducts which later will become either male or female reproductive organs. What is each of these duct systems called and which sex will each develop into?

The mesonephric ducts (wolffian ducts) develop into the male reproductive system. The paramesonephric ducts (müllerian ducts) develop into the female reproductive system.

Where is the SRY region found and approximately when does it become active?

The SRY is found in the short arm of the Y chromosome. The SRY gene becomes active around the end of week 6.

What organ and which hormone are ultimately produced after the SRY region becomes active?

After the SRY gene becomes active it ultimately produces the gonads (to be testes). The testes produce and secrete testosterone and müllerian-inhibiting factor.