"Meiosis and Fertilization" PPT courseware on the relationship between genes and chromosomes (Lesson 1 Meiosis)

Description

"Meiosis and Fertilization" PPT courseware on the relationship between genes and chromosomes (Lesson 1 Meiosis)

Part One: Curriculum Standard Requirements

Demonstrates that meiosis produces sperm and egg cells with half the number of chromosomes

Core competency docking

1. Concept of life - From the molecular and cellular levels, use the structural and functional perspectives to understand the behavior and quantitative changes of homologous chromosomes during meiosis.

2. Scientific thinking - Based on the concept of homologous chromosomes, be able to identify homologous chromosomes, non-homologous chromosomes and identical chromosomes in cell division images.

3. Scientific thinking - understand the characteristics of meiosis by comparing the similarities and differences between the sperm formation process and the egg cell formation process.

Meiosis and fertilization PPT, part 2: sperm formation process

Autonomous sorting

1. Form a place

______________.

2. Chromosome changes at various stages during sperm formation

(1) Interval

(2)Meiosis I

Result: 1 _______ cell divides into 2 ______ cells, the number of chromosomes is ______.

(3) Meiosis II

Result: After meiosis II, 2 ____________________ cells divide into 4 ____________.

(4) Deformation: 4 sperm cells undergo deformation to form 4 ____________.

3. Result: 1 spermatogonia → ____________ primary spermatocytes → ____________ secondary spermatocytes → ____________ sperm cells → ____________ sperm.

4. Several important concepts

(1) Homologous chromosomes

(2) Synapsis: The phenomenon of homologous chromosomes pairing ____________ during meiosis.

(3) Tetrad: Each pair of homologous chromosomes after synapsis contains 4 chromatids and is called a tetrad.

(4)Exchange

think

(1) During meiosis, does the halving of chromosome number occur in meiosis I or meiosis II? Why?

Tip: Meiosis I. Because the number of chromosomes in each secondary meiocyte produced after meiosis I is half that of the primordial germ cell, the number of chromosomes in each cell before and after meiosis II is equal.

(2) If interchange is not considered, will the number and type of chromosomes in the two sperm cells formed by one secondary spermatocyte after meiosis II be exactly the same? Why?

Tip: Exactly the same. Because meiosis II is equivalent to one mitosis, it just does not have homologous chromosomes. Therefore, according to the characteristics of mitosis, if exchange is not considered, one secondary spermatocyte will form two sperm cells after meiosis II. , the number and type of chromosomes are exactly the same.

[Typical Example 1] The following statement about homologous chromosomes is incorrect ()

A. One chromosome from the father and one from the mother

B. Two chromosomes copied from one chromosome

C. Two chromosomes that synapse during meiosis

D. Two chromosomes that are generally the same shape and size

Answer B

[Practice 1] During meiosis, homologous chromosomes separate and non-homologous chromosomes freely combine ()

A. Occurs simultaneously in the late stages of meiosis I

B. Occurs simultaneously in the late stages of meiosis II

C. Occurs at the end of meiosis II at the same time

D. Segregation occurs in meiosis I, and free association occurs in meiosis II.

Answer A

Meiosis and fertilization PPT, Part 3: The formation process of egg cells

Autonomous sorting

Comparison of sperm and egg cell formation processes

Same point

The behavior of chromosomes changes in the same way: that is, in interphase, chromosomes replicate first, and in meiosis I, homologous chromosomes ______, forming a tetrad, and non-sister chromatids can interchange; homologous chromosomes ______, non-homologous chromosomes Chromosomes assemble freely, and the number of chromosomes after meiosis I is ______; during meiosis II, sister chromatids separate.

think

Regardless of the difference between chromosomes and chromatin, which of the following cells contain homologous chromosomes?

① Somatic cells ② Cells during mitosis ③ Cells during meiosis I ④ Cells during meiosis II ⑤ Primordial germ cells ⑥ Mature germ cells

Tips ①②③⑤

[Typical Example 2] (2019 Xiangya Middle School Midterm) Which of the following is not the difference between the formation process of sperm and egg cells ()

A. The period when the number of chromosomes is reduced by half B. The number of secondary meroblasts

C. Distribution of cytoplasm D. Number of mature germ cells

Answer A

Meiosis and fertilization PPT, Part 4: The concept of meiosis

Autonomous sorting

Expansion: The reproductive method in which sperm and egg cells combine to form a fertilized egg, which then develops into a new individual, is called sexual reproduction, such as humans, cattle, peas, wheat, etc.; new individuals develop directly from somatic cells without fertilized eggs. Individual reproduction methods are called asexual reproduction, such as grafting, cuttings, etc.

[Typical Example 3] (2019·Yangzhou Academic Examination Simulation) The following statement about meiosis is incorrect ()

A. Meiosis occurs during the formation of sperm or egg cells

B. The number of chromosomes in the egg cell is only half that of the oogonia.

C. The chromosomes replicate once and the cell divides twice in succession.

D. Spermatogonia in the testis can only undergo meiosis.

Analysis: Spermatogonia in the testicles can produce new spermatogonia through mitosis and sperm cells through meiosis.

Answer D

[Practice 3] Which of the following statements about meiosis is correct ()

A. When organisms undergo sexual reproduction, they undergo meiosis.

B. The number of chromosomes in mature germ cells is halved because chromosomes do not replicate during meiosis.

C. Chromosomes and spindles do not appear during meiosis.

D. Cells can divide multiple times continuously during meiosis.

Analysis: Sexual reproduction includes two main processes: meiosis and fertilization. A is correct; the number of chromosomes in mature germ cells is halved because chromosomes are only copied once during meiosis and cells divide twice continuously. B is incorrect; Meiuosis Division is a special type of mitosis. Chromosomes and spindles appear during division. Error C. During meiosis, cells can only divide twice in a row. Error D.

Answer A

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For more information about "The Relationship between Genes and Chromosomes, Meiosis and Fertilization, Meiosis" PPT courseware, please click on the Relationship between Genes and Chromosomes, PPT Meiosis and Fertilization, PPT Meiosis PPT tag.

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Update Time: 2024-09-30

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