Biology 9 Lesson 11: Gametogenesis and fertilization
1. Theoretical Summary
Male gamete (sperm)
– 1 primordial male sex cell undergoes successive mitosis to produce spermatozoa.
– The spermatozoa to a certain period will move the germ cell layer close to the spermatogenesis tubule wall and grow to form primary spermatozoa.
Each primary spermatocyte undergoes meiosis 1 for 2 secondary spermatocytes.
- Each secondary spermatocyte undergoes meiosis 2 for 2 sperm.
Female gamete (eggs)
– A primitive female sex cell undergoes successive mitosis to produce oocysts.
– The oocyte develops into a primary oocyte.
+ Each primary oocyte undergoes meiosis 1 to give 1 secondary oocyte and 1 polar body.
- Each secondary oocyte through 2nd meiosis will give 1 egg and 1 second polar body.
- Each 1st polar body through meiosis 2 gives 2 2nd polar bodies.
- The polar bodies will disappear.
Fertilization is the random fusion of 1 male and 1 female gamete.
– The essence of fertilization is the union of two haploid sets (n chromosomes) to create a diploid nucleus (2n chromosomes) in the zygote.
1.3. Meaning of meiosis and fertilization
– Meiosis produces gametes containing a haploid set of chromosomes.
– Insemination restores diploid chromosome sets. The combination of the processes of mitosis, meiosis and fertilization ensures the stable maintenance of the chromosomes characteristic of sexually reproducing species.
– Meiosis produces many types of gametes with different origins, the random combination of different gametes, leading to the appearance of many combinatorial variations in sexually reproducing species, creating raw materials for breeding and evolution.
2. Illustrated exercise
– What are the similarities and differences between male and female gametogenesis?
- Germ cells (oocytes, spermatocytes) all carry out successive mitosis many times.
- Primary oocytes and primary spermatocytes both undergo meiosis to produce gametes.
3.1. Essay exercises
Question 1: What is fertilization? What does fertilization mean?
Verse 2: A fruit fly primordial cell (2n = 8) mitosis 4 times in a row. The resulting daughter cells participate in meiosis and spermatogenesis.
a) Determine the number of sperm produced?
b) How many chromosomes are present in sperm?
Question 3: Two chicken sex cells (2n = 78) mitosis in succession to produce cells with 39624 completely new chromosomes. The daughter cells produced in the last generation all reduce meiosis. Knowing the fertilization efficiency of gametes is 1.5625% and 32 zygotes are produced.
a. Determine the number of mitotic episodes of the above-mentioned sex cells.
b. Determine the sex of the above individual.
3.2. Multiple choice exercises
Question 1: During gametogenesis in animals, the activities of the germ cells are:
D. Mitosis and meiosis
Verse 2: From a primary oocyte undergoing meiosis, it produces:
A. 1 egg and 3 polar bodies
B. 4 eggs
C. 3 eggs and 1 polar body
D. 4 polar bodies
Question 3: Which of the following is incorrect?
A. Each sperm fuses with an egg to create a zygote.
B. Fertilization is the process of combining the haploid chromosome set of the male gamete with the female gamete to restore the diploid chromosome set for the zygote.
C. Insemination is the process of combining the genetic factors of the father and the mother to the child.
D. Sperm produced through meiosis are fertilized with an egg to form a zygote.
Question 4: There is a primitive sex cell that mitosis 6 times. All daughter cells become oocytes. The eggs produced are all involved in fertilization. Knowing the fertilization efficiency of the egg is 18.75% and that of the sperm is 6.25%. The number of zygotes formed and the number of male gametocytes involved in fertilization are:
A. 10 and 192.
B. 8 and 128.
C. 4 and 64.
D. 12 and 192.
Question 5: A species has a set of 2n=36 chromosomes. A mature sex cell of the double-infected mutant undergoes meiosis. If the pairs of chromosomes segregate normally, how many chromosomes are in the cell after meiosis I?
After completing this lesson, you should:
- Understand the mechanism of gametogenesis and fertilization.
- State the meaning of meiosis and fertilization.
- State the similarities and differences between male and female gametogenesis.
- Analyze the significance of the processes of meiosis and fertilization in terms of heredity and variation.