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

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

Doubts about having a boy or girl

Scene 1: In the hospital, after the doctor delivers a newborn, the first thing he says is to tell the mother whether the baby is a boy or a girl;

Scene 2: I heard that someone had a baby, and people couldn’t help but ask, “Is it a boy or a girl?”

Why do some individuals who develop from fertilized eggs develop into females and some into males?

1. Differences in chromosomes between men and women

After research, scientists believe that the reason for the difference between men and women is the difference in their chromosomes

What is gender determined by?

In 1902, American cytologist McCrone discovered during his observation that a pair of chromosomes in male somatic cells had a different shape from other chromosomes. He called this pair of chromosomes sex chromosomes;

In 1905, American cytologist Wilson further named the distinctive pair of chromosomes in male somatic cells the X chromosome and the Y chromosome, while the same pair of chromosomes in female somatic cells were the same, both X chromosomes.

Discussion(p38)

1. Among the 23 pairs of chromosomes in males and females, which pair is called the sex chromosomes?

Answer: The 23rd pair, related to gender, is called sex chromosomes

2. Among the two pictures above, which one shows the male chromosomes? Which picture shows female chromosomes?

Answer: The chromosomes on the left are male and the chromosomes on the right are female (male on the left and female on the right)

3. Which chromosome in the picture is the Y chromosome? What are its main morphological differences from the X chromosome?

Answer: The smaller one, the X chromosome is larger and the Y chromosome is smaller.

Sex ratio imbalance:

1. According to the fifth national census, the sex ratio of male to female babies born in Hainan Province is 135.64 to 100, ranking the highest in the country.

2. Guangdong has the second highest gender ratio in the country, 130.30 to 100, which is seriously high.

3. The sex ratio at birth between boys and girls in our country continues to rise. Population experts predict that there will be 30 million bachelors in our country by 2020.

What are the consequences of an imbalanced sex ratio in the population?

The imbalanced sex ratio of babies at birth seriously hinders the harmonious, sustainable and healthy development of our country's population, and will greatly lead to illegal and criminal activities such as marriage-buying and trafficking in women, as well as various complex social problems.

Class exercises

1. Theoretically, the possibility of having a boy or girl is ( )

A. 1:1 B. 2:1

C. 3:1 D. 4:1

2. If a couple gives birth to a girl in their first child, then the probability of a boy in their second child is ()

A. 50% B. 100%

C. 75% D. 25%

3. If a trait is always passed from father to son, and from son to grandson. Then you can speculate that the gene controlling this trait is in ( )

A. On the autosomes B. On the X chromosome

C. On the Y chromosome D. On the sex chromosome

4. A couple gave birth to a beautiful little girl. The sex-determining factor in the little girl’s cells is ( )

A cell membrane B cytoplasm

C Y chromosome D sex chromosome

5. The composition of chromosomes in human sperm can be expressed as: ( )

A 22+X B 22+Y

C 22 bars+X or 22 bars+Y D 22 pairs+XY

True or False

1. The responsibility of giving birth to a boy or a girl lies entirely with women. ( )

2. There are only genes that determine gender on the sex chromosomes. ( )

3. Each pair of chromosomes in biological cells comes from the father and the mother, so biological offspring have the genetic material of both parents. ( )

4. The gender of the newborn mainly depends on the sperm and egg cells. ( )

5. There are 23 pairs of chromosomes in the somatic cells of both men and women, and there are 23 pairs of chromosomes in the reproductive cells. Therefore, the chromosomes of men and women are exactly the same. ( )

6. The 23rd pair of human chromosomes is called the sex chromosomes. ( )

7. Men can produce two types of sperm containing X chromosomes and two types of sperm containing Y chromosomes at the same time; women only produce one type of egg cells containing X chromosomes. ( )

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