"Mendel's Pea Hybrid Experiment (1)" PPT courseware on the discovery of genetic factors (verification of the explanation of segregation phenomena and the law of segregation in the second lesson)

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"Mendel's Pea Hybrid Experiment (1)" PPT courseware on the discovery of genetic factors (verification of the explanation of segregation phenomena and the law of segregation in the second lesson)

Part One: Course Standard Requirements

Elucidate that the separation and free combination of genes in sexual reproduction gives rise to multiple possibilities for genotypes and phenotypes in offspring, and can thus predict the genetic traits of offspring

Core competency docking

1. Concept of life - through the process of hypothesis-deduction analysis, the scientific concept that biological traits are controlled by genetic factors is formed.

2. Scientific inquiry - by analyzing the principle of test crossing, understand the role of test crossing, and be able to clarify the process of Mendel's use of test crossing experiments to verify his explanation of the separation phenomenon.

3. Scientific thinking - By analyzing the hybridization experiment of a pair of genetic factors, using the hypothesis-deduction method, analyze how to implement the basic steps of hypothesis-deduction in the hybridization experiment of a pair of genetic factors.

4. Social Responsibility - Able to use Mendel's law of segregation and determine the genetic factor composition of the offspring and the type and proportion of trait expressions of the offspring based on the known genetic factor composition of the parents; and be able to infer the genetic factor composition of the parents based on the trait expression and proportion of the offspring.

Mendel's pea hybridization experiment PPT, Part 2: Verification of the explanation of the segregation phenomenon

Autonomous sorting

think

(1) Why can test crossing be used to determine the types and proportions of gametes that an individual to be tested can produce?

Tip: Test cross refers to the cross between the individual to be tested and a recessive homozygote, and the recessive homozygote can only produce recessive gametes. Therefore, the type and proportion of trait expression in the offspring of the test cross depends on the obvious traits produced by the parent to be tested. Types and proportions of recessive gametes.

(2) How to determine the genetic factor composition of the parent to be tested based on the trait performance of the test cross offspring?

It is suggested that if the test cross offspring all show dominant traits, then the parent to be tested is dominant homozygous; if the test cross offspring all show recessive traits, the parent to be tested is recessive homozygous; if the test cross offspring show dominant Sexual trait: recessive trait = 1:1, then the parent to be tested is heterozygous.

[Typical Example 1] A pair of homozygous parents with opposite traits are crossed to obtain F1. Let F1 conduct a test cross with the recessive individual, and nothing can be learned through the test cross experiment ()

A.Chemical structure of F1-related genetic factors B.Types of gametes produced by F1

C.F1 genetic factor composition D.Proportion of gametes produced by F1

Analysis: The test cross experiment can verify the genetic factor composition of F1, the types and proportions of gametes produced by F1, but it cannot verify the chemical structure of F1-related genetic factors, A error.

Answer A

[Practice 1] The red flowers of a certain plant are dominant to the white flowers, and are controlled by a pair of genetic factors A and a. In order to determine the genetic factor composition of a certain red flower plant, it is crossed with another white flower plant to obtain enough hybrid offspring. Which of the following related statements is wrong ()

A. The hybridization method between the red flower plant and the white flower plant to be tested is a test cross.

B. If the offspring are all safflower, the genetic factor composition of the safflower plant to be tested is AA

C. If white flowers appear in the offspring, the genetic factor composition of the safflower plant to be tested is Aa

D. If white flowers appear in the offspring, the proportion of white flower plants in the offspring will be 1/4

Mendel's pea hybridization experiment PPT, the third part: the law of separation, hypothesis-deduction method

Autonomous sorting

1.The law of separation

In the somatic cells of organisms, the genetic factors that control _______________ exist in pairs and do not fuse; when gametes are formed, _______________ separates, and the separated _______________ enter into _______________ separately and are passed on to offspring along with the gametes. .

2. Hypothesis-deduction method

After raising a question on the basis of _______________, a hypothesis to explain the problem is put forward through _______________, _______________ based on the hypothesis, and then the conclusion is drawn through deductive reasoning through _______________.

Literacy improvement

1. Know the genetic factor composition of the parents, and find the genetic factor composition and proportion of the offspring.

Method 1: Directly use the separation ratio to derive

If it is known that both parents are heterozygous Dd, then it is heterozygous self-crossing, and the offspring DD:Dd:dd=1:2:1, dominant individual (D_):recessive individual (dd)=3:1. That is, DD accounts for 1/4 of the offspring, Dd accounts for 1/2, dd accounts for 1/4, dominant individuals account for 3/4, and recessive individuals account for 1/4.

Method 2: Calculate using the probability of gametes

If it is known that both parents are heterozygous Dd, what are the proportions of Dd individuals and dd individuals in the offspring? You can first calculate the types and proportions of female and male gametes produced by the female and male parents (female gametes: D: d = 1/2D: 1/2d; male gametes: D: d = 1/2D: 1/2d ), and then perform the following calculation:

The probability that the offspring is DD = probability of D female gametes × probability of D male gametes = 1/2 × 1/2 = 1/4;

The probability that the offspring is dd = the probability of d female gametes × the probability of d male gametes = 1/2 × 1/2 = 1/4;

The probability that the offspring is Dd = probability of D female gametes × probability of d male gametes + probability of d female gametes × probability of D male gametes = 1/2 × 1/2 + 1/2 × 1/2 = 1/2.

[Practice 2] People's double eyelids are dominant to single eyelids and are controlled by a pair of genetic factors D and d. A heterozygous couple with double eyelids have a boy and a girl. Theoretically, the probability that both the boy and the girl have single eyelids is ()

A.1 B.1/4 C.3/16 D.1/16

Analyzing Dd self-crossing, the probabilities of the offspring being DD, Dd and dd are 1/4, 1/2 and 1/4 respectively. DD and Dd both show double eyelids, while dd shows single eyelids, so the offspring show single eyelids. The probability is 1/4. The single and double eyelids of the two children are independent of each other and do not affect each other. Therefore, the probability that both children have single eyelids is equal to 1/4×1/4, or 1/16.

Answer D

2. Based on the genetic factor composition, trait expression and proportion of the offspring, the genetic factor composition type of the parents is estimated (indicated by the letters D and d)

Method 1: Separation ratio method

①If the segregation ratio of offspring traits is dominant:recessive=3:1, then the genetic factor composition of the parents is __________;

②If the segregation ratio of offspring traits is dominant:recessive=1:1, then the genetic factor composition of the parents is __________;

③If the offspring has only recessive traits, the genetic factor composition of the parents is __________;

④If the offspring has only dominant traits, the genetic factor composition of the parents is __________.

Method 2: Genetic factor filling method

First, write down the genetic factors that can be determined based on the performance of the parental traits. For example, the genetic factor composition of the dominant trait can be represented by D_, then the genetic factor composition of the recessive trait is only dd. According to the pair of genetic factors in the offspring, they come from Two parents can deduce unknown genetic factors in the parents.

Method Three: Implicit Homozygous Breakthrough Method

If there are recessive individuals in the offspring, it is often a breakthrough in the process of inverse deduction. Because the recessive individuals are homozygous (dd), there must be at least one recessive genetic factor d in the genetic factor composition of the parents, and then Further judgment is made based on the performance of parental traits.

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For more information about the PPT courseware "Mendel's discovery of genetic factors in pea hybridization experiments, verification of the explanation of segregation phenomena and the law of separation", please click Mendel's discovery of genetic factors in pea hybridization experiments, PPT verification of the explanation of segregation phenomena and the law of separation. PPT labels.

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