"Human Gender Inheritance" Biological Inheritance and Variation PPT Courseware 4

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"Human Gender Inheritance" Biological Inheritance and Variation PPT Courseware 4

Review the past and learn the new

Genes that control the inheritance of biological traits also exist in pairs on paired chromosomes. These paired genes are divided into recessive and dominant. That is to say, if a pair of genes are all dominant, the traits controlled by them will naturally be expressed, which is called dominant

Traits; if one of the paired genes is dominant and the other is recessive, the traits controlled by the pair of genes will only show dominant traits; only when the paired genes are recessive, the recessive traits will show up.

Evidence 1: Differences in male and female chromosomes

Review: Among the 23 pairs of chromosomes in male and female somatic cells, 22 pairs are autosomes, and the last pair is the sex chromosomes.

The scientist who discovered the sex chromosomes was American cytologist Michael Lang.

Differences in chromosomes between men and women

1. There are 23 pairs of chromosomes in the somatic cells of both men and women. One pair of chromosomes has obvious differences in shape and size (the shape and size of the other 22 pairs of chromosomes are basically the same). From this, it can be judged that the difference between men and women is related to this pair of chromosomes. Based on this This pair of chromosomes is called the sex chromosomes.

2. Among the pair of sex chromosomes in male somatic cells, the larger one is called the X chromosome and the smaller one is called the Y chromosome.

3. The pair of sex chromosomes in female somatic cells are basically the same size and shape, and are similar to the X chromosomes in male somatic cells. Through further research, scientists found that they are both X chromosomes.

Observe and think

1. The last pair of chromosomes are the sex chromosomes.

2. The left picture shows the chromosomes of male somatic cells, and the right picture shows the chromosomes of female somatic cells.

3. There are obvious differences in morphology between the Y chromosome and the X chromosome: the X chromosome is larger and the Y chromosome is smaller.

4. Both male sperm and female egg cells have only one sex chromosome. Men have two types of sperm, containing X and Y sex chromosomes respectively; women have only one type of egg cell, containing X sex chromosomes.

pass practice

In the germ cells produced by humans, the correct chromosome composition is ( )

A, 46+X B, 22+X or 22+Y

C, 44+Y D, 23+X or 22+Y

Sex chromosomes X and Y may exist at the same time ( )

A. In sex cells B. In sperm

C. In body cells D. In egg cells

Evidence 2: There are equal opportunities to give birth to a boy or a girl, and the decision is made by the man.

When men form sperm, the ratio of X chromosomes to Y chromosomes they form is 1:1, while women only produce eggs containing X chromosomes, so the male-to-female ratio of offspring is 1:1. And gender is determined by sperm.

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For more information about the PPT courseware "Inheritance of Biological Inheritance and Variation and Gender Inheritance in Humans", please click the Inheritance of Biology and Variation ppt Gender Inheritance in Humans ppt tag.

"Human Gender Inheritance" Biological Inheritance and Variation PPT Courseware 5:

"Human Gender Inheritance" Biological Inheritance and Variation PPT Courseware 5 Confused about giving birth to a boy or a girl Scene 1: In the hospital, after the doctor delivers a newborn, the first thing he says is to tell the mother whether the child is a boy or a girl; Scene 2: Listen When someone says they have a baby, people...

"Human Gender Inheritance" Biological Inheritance and Variation PPT Courseware 3:

"Human Gender Inheritance" Biological Inheritance and Variation PPT Courseware 3 1. Among the two pictures, which picture shows the male chromosomes? Which picture shows female chromosomes? What's the difference between them? The first picture shows the male chromosomes, the second...

"Human Gender Inheritance" Biological Inheritance and Variation PPT Courseware 2:

"Human Gender Inheritance" Biological Inheritance and Variation PPT Courseware 2 Review Questions: 1. Is human gender a trait? 2. What controls traits? 3. Where are genes located in cells? Question outline: (1) Which pair of chromosomes in males and females has...

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Update Time: 2024-07-29

This template belongs to biology courseware People's Education Edition Biology for Grade 8, Volume 2 industry PPT template

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