Unraveling the Mystery of Chromosomal Crossover: A Meiosis I Deep Dive

Biology Grades High School 12:15 Video
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Lesson Description

Explore the intricacies of chromosomal crossover during Meiosis I, a key process driving genetic diversity. Learn about homologous chromosomes, tetrads, and the significance of recombination in creating unique offspring.

Video Resource

Chromosomal crossover in Meiosis I

Khan Academy

Duration: 12:15
Watch on YouTube

Key Concepts

  • Meiosis I
  • Chromosomal Crossover (Homologous Recombination)
  • Homologous Chromosomes and Tetrads
  • Genetic Variation

Learning Objectives

  • Students will be able to define and differentiate between mitosis and meiosis and describe the role of germ cells.
  • Students will be able to describe the events of prophase I, including synapsis and crossing over.
  • Students will be able to explain how chromosomal crossover contributes to genetic diversity.
  • Students will be able to define homologous chromosomes, sister chromatids, and tetrads.

Educator Instructions

  • Introduction (5 mins)
    Begin by reviewing the basics of cell division, mitosis and meiosis, and the purpose of each. Briefly introduce the concept of genetic variation and its importance in evolution.
  • Video Viewing (15 mins)
    Play the Khan Academy video 'Chromosomal crossover in Meiosis I'. Encourage students to take notes on key terms and processes.
  • Guided Discussion (15 mins)
    Facilitate a class discussion to clarify any confusion and reinforce understanding of the video's content. Focus on the steps of prophase I and the mechanism of chromosomal crossover.
  • Activity: Modeling Crossover (15 mins)
    Have students use pipe cleaners or other manipulatives to model the process of chromosomal crossover. This hands-on activity will solidify their understanding of the exchange of genetic material.
  • Wrap-up and Assessment (10 mins)
    Review the key concepts of the lesson and administer a short quiz to assess student understanding.

Interactive Exercises

  • Chromosomal Crossover Modeling
    Students use different colored pipe cleaners to represent homologous chromosomes. They physically model the breaking and rejoining of segments to simulate chromosomal crossover. This will help to visualize the exchange of genetic information.

Discussion Questions

  • What is the difference between mitosis and meiosis, and why is meiosis necessary for sexual reproduction?
  • Describe the process of chromosomal crossover. What is its purpose, and why is it important?
  • What are homologous chromosomes, and how do they differ from sister chromatids?
  • How does chromosomal crossover contribute to genetic variation within a population?

Skills Developed

  • Critical Thinking
  • Visual Learning
  • Conceptual Understanding
  • Scientific Communication

Multiple Choice Questions

Question 1:

What is the main purpose of meiosis?

Correct Answer: Production of gametes

Question 2:

During which phase of meiosis does chromosomal crossover occur?

Correct Answer: Prophase I

Question 3:

What are homologous chromosomes?

Correct Answer: Chromosome pairs with genes for the same traits

Question 4:

What is a tetrad?

Correct Answer: A group of four chromatids

Question 5:

What is the result of chromosomal crossover?

Correct Answer: Increased genetic diversity

Question 6:

What is a germ cell?

Correct Answer: A cell that produces gametes

Question 7:

What is the diploid number of a cell?

Correct Answer: The full number of chromosomes

Question 8:

What structure holds sister chromatids together?

Correct Answer: Centromere

Question 9:

What is the term for the location where crossing over occurs?

Correct Answer: Chiasma

Question 10:

Why is genetic variation important?

Correct Answer: It helps species adapt to changing environments

Fill in the Blank Questions

Question 1:

A cell that can undergo meiosis to produce gametes is called a __________ cell.

Correct Answer: germ

Question 2:

The diploid number refers to the __________ number of chromosomes in a cell.

Correct Answer: full

Question 3:

During interphase, the DNA __________ before cell division.

Correct Answer: replicates

Question 4:

Meiosis I begins with a phase called __________, during which chromosomal crossover occurs.

Correct Answer: prophase I

Question 5:

Homologous chromosomes pair up to form a __________ during prophase I.

Correct Answer: tetrad

Question 6:

Chromosomal crossover is also known as homologous __________.

Correct Answer: recombination

Question 7:

__________ chromosomes contain genes for the same traits.

Correct Answer: homologous

Question 8:

Sister __________ are identical copies of a chromosome.

Correct Answer: chromatids

Question 9:

The site of crossing over is called the __________.

Correct Answer: chiasma

Question 10:

Chromosomal crossover leads to increased __________ __________ within a population.

Correct Answer: genetic variation

Educational Standards

B.LS3.1:Ask questions to clarify relationships about the role of DNA and chromosomes in coding the instructions for characteristic traits passed from parents to offspring. B.LS3.2:Make and defend a claim based on evidence that inheritable genetic variations may result from: (1) new genetic combinations through meiosis, (2) viable errors occurring during replication, and/or (3) mutations caused by environmental factors. B.LS4.2:Construct an explanation based on evidence that biological diversity is influenced by (1) the potential for a species to increase in number, (2) the heritable genetic variation of individuals in a species due to mutation and sexual reproduction, (3) competition for limited resources, and (4) the proliferation of those organisms that are better able to survive and reproduce in the environment.

Teaching Materials

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