Human Biology (Production of Gametes)

Question 1

What is gamateogenesis?

Answer 1

Gamete development, from meiosis to mature gametes.

Question 2

What are the 2 types of gamaetogenesis?

Answer 2

Formation of spermatozoa in the testis is called spermatogenesis and formation of ova in the ovary is called oogenesis.

Question 3

Where does spermatogenesis occur? And around how long?

Answer 3

In the seminiferous tubules of each testis. around 72 days and occurs
continuously after puberty.

Question 4

Describe the process of Spermatogenesis

Answer 4

1. The lining of the seminiferous tubules, are filled with immature cells called spermatogonia which contain diploid numbers of chromosomes.
2. At puberty these cells begin dividing by mitosis and produce new cells for the production of sperm.
3. Some cells move into the centre of the tubules where they undergo a period of growth.
4. The enlarged cells are now termed primary spermatocytes.
5. These still diploid cells, divide complete the 1st stage of meiosis to form haploid secondary spermatocytes.
6. The secondary spermatocytes complete the 2nd meiotic division and produce 2 spermatids.
7. These spermatids then mature to form spermatozoa.
   Therefore in spermatogenesis, 4 spermatozoa are produced from a single spermatogonium.

Question 5

Describe the process of Oogenesis

Answer 5

1. The diploid oogonia in the female develop first into ovaries.
2. The oogonia by the time of birth have undergone growth to become primary oocytes.
3. The primary oocyte then begins prophase, but stops, so at birth they are still in prophase.
4. At puberty, the follicle maturation begins, and the primary oocyte begins to complete the stage of the first division of meiosis, producing two haploid cells.
5. The two cells are the secondary oocyte, which receives half the chromosomes but majority of the cytoplasm, and the other is a polar body which recieves the other half of chromosomes but less cytoplasm.
6. The secondary oocyte begins the second divison of meiosis but stops at metaphase.
7. Then ovulation occurs, with the follicle rupturing and the secondary oocyte and polar body being expelled into the uterine tube.
8. If penetrated by a spermatozoon then meiosis is completed, producing a second polar body, and an ovum which develops into an egg.
   Therefore, oogenesis produces a single ovum from each primary occyte.

Question 6

When are oogonia formed?

Answer 6

Before a female is born, millions of oogonia are formed.

Question 7

What is around the primary oocyte during the beginning of prophase?

Answer 7

The primary oocytes are surrounded by a single layer of cells, forming a primary follicle.