"Dominant and Recessive Genes" Biological Inheritance and Variation PPT Courseware 4

Description

"Dominant and Recessive Genes" Biological Inheritance and Variation PPT Courseware 4

learning target:

1. Give examples of the relationship between relative traits and genes, and describe the transmission characteristics of a pair of genes that control relative traits.

2. Explain the dangers of marriage between close relatives.

3. Strengthen the scientific attitude of seeking truth from facts and use scientific methods to explain relevant issues in life sciences.

The three genotypes (combinations) only express two relative traits, namely AA. Aa expresses ______; while aa expresses ______.

Mendel (G.J.Mendel,1822-1884), Austrian. Born in a poor peasant family, he loved working, natural science and mathematics since he was a child. During the seven years from 1858 to 1865, he conducted hybrid experiments on various plants and made significant contributions to genetics.

summary:

1. Relative traits are divided into dominant and recessive traits. The traits of the parents that are expressed in the offspring are dominant traits, and the traits that are not expressed are recessive traits.

2. Dominant traits are controlled by dominant genes and are generally represented by English capital letters (such as A). Recessive traits are controlled by recessive genes and are generally expressed by the same English lowercase letters (such as a).

3. Those whose genetic composition is AA or Aa are dominant traits, and those whose genetic makeup is aa are recessive traits.

4. When a dominant gene and a recessive gene exist at the same time, only the traits controlled by the dominant gene will be expressed.

2. Why is it forbidden to marry close relatives?

my country’s Marriage Law stipulates that marriage is prohibited between direct blood relatives and collateral blood relatives within three generations.

The same family is more likely to carry the same recessive disease-causing gene. If the offspring get married, the chance of combining the recessive disease-causing genes will be greater, and the chance of developing genetic diseases will be greatly increased.

Cases: 1. In January 1839, 30-year-old Darwin married his cousin Emma. Three of their six children died in infancy, and the other three were infertile.

2. In February 1840, the 21-year-old Queen Victoria married her cousin (uncle's second son) Albert. Unexpectedly, this marriage would bring great misfortune to their lives. They gave birth to nine children in total, four of them. There are five boys and five girls. Three of the four boys are suffering from the genetic disease - hemophilia. Girls also carry the gene of this disease. Hemophilia was called the "royal disease" at that time.

3. Geneticist Morgan also had a marriage that should not have happened. The two daughters he had after marrying his cousin Mary both had "inexplicable dementia" and died prematurely. The only boy also had obvious intellectual disabilities. .

Current status of genetic disease in my country:

1. The proportion of patients with genetic diseases in my country’s total population: 20%-25%

2. About 1.3% of newborns have congenital genetic defects

3. About 50% of spontaneous abortions are caused by chromosomal abnormalities!

4. There are more than 1 million people suffering from Trisomy 21 in the Chinese population.

5. Chromosome variation alone causes 520,000 spontaneous abortions every year.

Dangers of genetic diseases

It endangers human health and reduces the quality of the population; it brings serious economic and mental burdens to the patients, their families and society; some mental patients bring harm to social security.

Environmental pollution is the main reason for the increasing incidence of genetic diseases.

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For more information about the PPT courseware "Inheritance of Biology and Dominant and Recessive Gene Variation", please click the Dominant and Recessive ppt tab of Biological Inheritance and Variation ppt Genes.

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Update Time: 2024-11-23

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

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