"DNA Replication" The Nature of Genes PPT

Description

"DNA Replication" The Nature of Genes PPT

Part One: Curriculum Standard Requirements

1. Understand the early speculations of Watson and Crick on the mode of DNA replication and the experimental evidence of semi-conservative replication of DNA.

2. Elucidate the conditions, processes and characteristics of DNA replication.

Literacy requirements

1. Concept of life: Accurately understand the characteristics of DNA replication and understand the laws of life activities.

2. Scientific thinking: Summarize the ideas and rules of scientific research.

DNA Replication PPT, Part 2: Text Analysis

1. Speculation on DNA replication and experimental evidence of DNA semi-conservative replication

Basic review · Consolidate the foundation of teaching materials

1. Speculations on DNA replication

(1) Proposed by: _____________.

(2)Hypothesis

① Unwinding: During DNA replication, the DNA double helix unwinds and the ________ between complementary bases breaks.

② Replication: The unraveled ________ serves as the template for replication, and the free deoxynucleotide binds to the single strand serving as the template by forming _________ according to the principle of _________.

(3) Characteristics: Each newly synthesized DNA molecule retains one strand of the original DNA molecule. This replication method is called ______________.

2. Experimental evidence for semi-conservative replication of DNA

(1) Experimental methods: isotope labeling technology and centrifugation technology.

(2) Experimental principle

① If both strands of DNA are labeled with 15N, then the density of such DNA molecules is the highest and should be at the ______ part of the test tube during centrifugation.

② Neither strand of DNA is labeled with 15N, so the density of such DNA molecules is the smallest and should be at the ______ part of the test tube during centrifugation.

③Only one single strand of the two DNA strands is labeled with 15N, so such DNA molecules should be in the ______ part of the test tube when centrifuged.

(3) Experimental process

(4)Experimental results

① Take it out immediately, extract DNA → centrifuge → ____________.

② Take it out after one generation of reproduction, extract DNA → centrifuge → ______ medium band.

③ Take it out after two generations of breeding, extract DNA → centrifuge → light band and medium band.

(5) The experimental results are consistent with expectations, indicating that DNA replication proceeds in a ____________ manner.

Judgment of right and wrong · Correction is easy to be confused and easy to make mistakes

(1) Watson and Crick proved that the replication method of DNA molecules is semi-conservative replication ()

(2) Experiments proving semi-conservative replication of DNA used isotope labeling technology and centrifugation technology ()

Deepen exploration and solve problems

The DNA molecules of E. coli grown on media with nitrogen sources of 14N and 15N are 14N-DNA (relative molecular mass a) and 15N-DNA (relative molecular mass b) respectively. Transfer the parent E. coli to a medium containing 14N, then multiply it for two consecutive generations (Ⅰ and Ⅱ), and use a certain centrifugation method to separate the results as shown in the figure below.

1. What is the structure of the DNA molecule of Generation I bacteria?

Tip: Only one strand in the first-generation bacterial DNA molecule is labeled with 15N.

2. What is the average relative molecular mass of III-generation bacterial DNA molecules?

Tip: The average relative molecular mass of III-generation bacterial DNA molecules is 7a+b/8.

2. The process of DNA replication

Basic review · Consolidate the foundation of teaching materials

1.The concept of DNA replication

The process of synthesizing ____________ using ____________ as a template.

2. Period of occurrence

In eukaryotes, this process is completed with the replication of chromosomes during the ____ stage before cell division.

3. Process

4.Results

Two ____________ DNA molecules are formed.

5.Features

(1)__________________ .

(2)______copy.

6. Meaning: ____________ is passed from parent cells to daughter cells, thus maintaining the continuity of ______.

Judgment of right and wrong · Correction is easy to be confused and easy to make mistakes

(1) Each deoxynucleotide strand after DNA unwinding can be used as a template for DNA replication ()

(2) After the DNA double helix is ​​completely unwound, DNA replication begins ()

(3) During DNA replication, helicase destroys hydrogen bonds and cannot break down DNA into deoxynucleotides ()

Deepen exploration and solve problems

1. Does DNA replication only occur during mitosis and meiosis? Does it only occur in the nucleus?

Tip: No, DNA replication also occurs during amitosis. There is also DNA in mitochondria and chloroplasts, and DNA replication is also carried out.

2. During DNA replication, where does helicase act on the DNA?

Hint: Helicases act on hydrogen bonds connecting base pairs.

DNA Replication PPT, Part 3: In-class Practice Knowledge Implementation

1. After Watson and Crick published their paper on the double helix structure of DNA, they proposed the hypothesis of DNA self-replication. Which of the following statements about the content of this hypothesis is incorrect?

A. During DNA replication, the double helix unwinds and the hydrogen bonds between complementary bases are broken.

B. Using the two unraveled single strands as templates and free deoxynucleotides as raw materials, based on the principle of complementary base pairing,

Binds to a single strand as a template via hydrogen bonding

C. The formed DNA molecule includes a template single strand and a new strand

D. The two DNA molecules formed are composed of two parent strands and two daughter strands combined respectively.

2. (2019·Fujian Xiamen First Intermediate School) Which of the following statements about DNA replication is incorrect?

A. When DNA replicates, only one strand of DNA is used as a template.

B. During DNA replication, four kinds of free deoxynucleotides are used as raw materials.

C. The DNA replication process requires energy

D. The replication method of DNA molecules is semi-conservative replication

3. The following correct sequence for the DNA replication process is

① The hydrogen bonds between complementary base pairs are broken ② The hydrogen bonds are formed between complementary base pairs ③ The DNA molecules are unwound under the action of helicase ④ The unwinding parent strand is used as a template for complementary base pairing ⑤ The daughter strand is The parent chain coils into a double helix structure

A.①③④②⑤ B.①④②⑤③

C.①③⑤④② D.③①④②⑤

4. (2019·Chengdu High-tech Experimental Middle School High School Entrance Examination in February) Using one strand of DNA "—A—T—C—" as a template, the daughter strand produced after replication is

A.—G—A—T— B.—U—A—G—

C.—T—A—G— D.—T—U—G—

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Update Time: 2024-06-29

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