16 Questions
What is the term for the loss of a segment of a chromosome?
Deletion
At what week of development do the primordial gonadal cells migrate to the genital ridges?
4 weeks
What is the gene responsible for the differentiation of the undifferentiated sex cords into the primitive testis?
SRY gene
What is the term for the process by which immature oocytes are distributed throughout the ovary in follicles?
Folliculogenesis
How many follicles are present in each human ovary?
200,000 to 400,000
What is the term for the production of sperm?
Spermatogenesis
Where are the primordial follicles most prevalent in the ovary?
Stroma
What is required for the differentiation of primordial germ cells into an unfertilized egg?
Proliferation and growth in size
What is the process by which germ cells are converted into male and female gametes?
Gametogenesis
What is the end result of meiosis?
Two haploid daughter cells
What is the term for the union of male and female gametes?
Zygote
How many chromosomes are present in each gamete?
23 chromosomes
What is the term for the process where a part of a chromosome breaks off and is attached to another?
Translocation
What occurs during meiosis I?
Reduction in chromosomal number
What is the result of non-disjunction during meiosis?
One gamete with 24 chromosomes and one with 22 chromosomes
What is the term for the process of cell division that gives rise to two genetically identical daughter cells?
Mitosis
Study Notes
Gametogenesis
- Gametogenesis is the conversion of germ cells into male and female gametes
- Male gamete: sperm
- Female gamete: oocyte
- Zygote: union of male and female gametes
Somatic Cell and Gametes
- Somatic cells have 46 chromosomes (23 pairs), including 22 pairs of autosomes and 1 pair of sex chromosomes
- Each gamete (maternal and paternal) contains a haploid number of 23 chromosomes
Phases of Gametogenesis
- Four phases: origin and migration of germ cells, increase in number of germ cells by mitosis, reduction in chromosomal number by meiosis, and structural and functional maturation of eggs and sperm
Mitosis and Meiosis
- Mitosis: process where a cell divides to produce two genetically identical daughter cells
- Meiosis: process that takes place in germ cells to produce gametes, requiring two cell divisions (Meiosis I and Meiosis II)
Chromosomal Abnormalities
- Numerical abnormalities: non-disjunction leads to formation of daughter cells with unequal chromosome numbers (trisomy or monosomy)
- Structural abnormalities: do not affect total chromosome number, but have serious consequences, including translocation and deletion
Early Development of Gametes
- In human embryos: undifferentiated primordial gonadal cells (PGC) are seen in the epithelium of the yolk sac at 3 weeks, and migrate to the genital ridges at 4 weeks
- PGC induce the genital ridge to differentiate into a primitive germinal epithelium, forming primary sex cords
- At 8 weeks, ovary and testis are histologically distinct
Oogenesis
- Oogenesis produces ova
- Oogonium differentiates into ovum
- Immature oocytes are distributed throughout the ovary in follicles, with a total of 200,000 to 400,000 follicles present in each human ovary
- Only a few oogonia reach maturity, with fewer than 400 oocytes maturing and being released by ovulation in humans
- Location of oocyte depends on its maturity, with primordial follicles most prevalent in the stroma and oocytes becoming more centrally located as they mature
Understand the process of gametogenesis, including the formation of male and female gametes, and the differences between somatic cells and gametes. Learn about the phases of gametogenesis and the union of gametes to form a zygote.
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