Week 8 Masculinized Reproductive System

Germ cells known as Gamates

• Sperm in male, oocytes in women

• gonads produce gametes and secrete sex hormones

Offspring

Two haploid gamates fuse to form a diploid zygote.

Male gamete has motility, contains Y chromosome

Female gamete contains nutrients for developing zygote, contains X chromosome

Primary sex organs

• Organs that produce the gametes (testes or ovaries)

Secondary sex organs (essential for reproduction)

• Male is ducts, glands, and the penis that deliver the sperm cells

• Female is uterine tubes, uterus, vagina, that receive the sperm and nourish fetus

Secondary sex characteristics

• Public, axillary and facial hair, scent glands, body morphology, and low-pitches voice in males

Sex Chromosomes (Gametes) Role

• Our sperm or egg cells are haploid; they contain 23 individual chromosomes

  • 22 autosomes

  • 1 pair of sex chromosomes (XY males; XX females)

  • all eggs carry the X chromosome

• Sex of the child is determined by the type of sperm that fertilizes the mother’s egg

Sex differentiation

• Gonads begin to develop at 6 weeks as gonadal ridges

• 2 sets of ducts at that time

• SRY gene (sex determining region of Y gene)

  • in males, codes for a protein that causes development of the testes

• female development occurs in absence of male or female hormones

Androgen insensitivity syndrome

• genetically male

• testosterone is secreted

• target cells lack receptors for the hormone

• no masculinizing effects occur

Somatic cells (diploid cells)

• 23 pairs of chromosomes for a total of 46

  • each pair is homologous since contain similar genes in same order

  • one member of each pair is from each parent

• 22 autosomes and 1 pair of sex chromosomes

  • sex chromosomes are either X or Y

  • females have two X chromosomes

  • males have an X and a smaller Y chromosome

• produced by mitosis

Gametes (haploid cells)

• single set of chromosomes for a total of 23

• produces by special type of division called meiosis

Meiosis I — Prophase I

• chromosomes become visibile, mitotic spindle appears, nuclear membrane and nucleoli disappear

• events not seen in prophase or metaphase of meiosis II

  • synapsis: all copies of homologous chromosomes pair off forming a tetrad

  • crossing over: portions of chromatids are exchanged between any members of the tetrad and parts of maternal chromosomes may be exchanged with paternal ones

• genetic recombination produces gametes unlike either parent

  

Meiosis I — Metaphase I, Anaphase I, and Telophase I

In metaphase I, homologous pairs of chromosomes line up along metaphase plate with attached microtubules

In anaphase I, each set of homologous chromatids held together by a centromere are pulled to opposite ends of the dividing cell

Telophase I and cytokinesis are similar to mitotic division

Result is 2 cells with haploid number of chromosomes