3.Genetics

 

Essential Idea:

  1. Every living organism inherits a blueprint for life from its parents in the form of genes carried on chromosomes.
  2. Chromosomes carry genes in a linear sequence that is shared by members of a species.
  3. The inheritance of genes follows predictable patterns governed by the laws of inheritance discovered by Gregor Mendel.
  4. Meiosis leads to the independent assortment of chromosomes and the unique composition of alleles in daughter cells, creating genetic variation.
  5. Genetic variation is essential for species to adapt and evolve in response to changing environmental conditions.

 

Statement of Inquiry:The inheritance of genes follows predictable patterns that can be analyzed through the study of genetic crosses, pedigree analysis, and an understanding of the molecular mechanisms underlying the transmission of genetic information from parents to offspring.

 

Assessment : 

3. Genetics

3.1 Genes

3.2 Chromosomes

3.3 Meiosis

3.4 Inheritance

3.5 Genetic Modification and Biotechnology

3.1 Genes
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3.2 Chromosomes
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3.3 Meiosis

3.4 Inheritance

3.5 Genetic Modification and Biotechnology

Unit Lesson Plan

Here is a more detailed lesson plan and content overview for an IB Diploma Programme (DP) Standard Level (SL) genetics unit:

Genetics and Inheritance (IB DP Biology SL)

Unit Duration

  • Approximately 10-12 hours of instructional time

Unit Objectives

By the end of this unit, students will be able to:

  • Explain the role of genes, chromosomes, and genetic variation in inheritance
  • Describe the process of meiosis and its importance in creating genetic diversity
  • Analyze patterns of inheritance, including Mendelian genetics and sex-linked traits
  • Apply principles of genetics to solve problems and interpret genetic data

Lesson 1: Introduction to Genetics

  • Genes and the human genome project
  • Genetic mutations and disorders (e.g. sickle cell anemia)
  • Teacher notes:
    • Emphasize the importance of the human genome project in advancing our understanding of genetics
    • Discuss how genetic mutations can lead to genetic disorders, using sickle cell anemia as an example

Lesson 2: Chromosomes and Genetic Sequencing

  • Structure and function of chromosomes
  • Karyotypes and genome size
  • Teacher notes:
    • Explain the role of chromosomes in carrying genetic information
    • Introduce karyotype analysis as a tool to identify chromosomal abnormalities

Lesson 3: Meiosis and Genetic Variation

  • Meiosis and the creation of genetic diversity
  • Review of the meiosis process
  • Teacher notes:
    • Emphasize how meiosis leads to the independent assortment of chromosomes and the unique composition of alleles in daughter cells
    • Provide opportunities for students to review and apply their understanding of the meiosis process

Lesson 4: Patterns of Inheritance

  • Mendelian inheritance (dominant, recessive, codominance, incomplete dominance)
  • Sex-linked traits
  • Teacher notes:
    • Introduce Mendelian genetics and the concepts of dominant, recessive, codominance, and incomplete dominance
    • Explain the inheritance of sex-linked traits, such as color blindness and hemophilia

Lesson 5: Extensions of Genetics

  • Dihybrid inheritance and the Punnett square
  • Polygenic inheritance and quantitative traits
  • Chi-squared analysis for genetic data
  • Linked genes and genetic recombination
  • Teacher notes:
    • Explore more complex patterns of inheritance, such as dihybrid crosses and polygenic traits
    • Introduce chi-squared analysis as a tool to evaluate the statistical significance of genetic data
    • Discuss the concept of linked genes and how genetic recombination can affect inheritance

Practical Work

  • Karyotype analysis
  • Genetic crosses and pedigree analysis
  • Population genetics and Hardy-Weinberg equilibrium
  • Teacher notes:
    • Provide opportunities for students to apply their knowledge through hands-on practical activities
    • Emphasize the importance of data collection, analysis, and interpretation in the context of genetics

Assessment

  • Formative assessments (e.g. worksheets, quizzes, discussions)
  • Summative assessment (e.g. end-of-unit test covering core topics and skills)
  • Teacher notes:
    • Use a variety of formative assessments to monitor student understanding throughout the unit
    • Design the summative assessment to evaluate students' mastery of the unit's learning objectives

Unit Objectives

By the end of this unit, students will be able to:

  • Explain the role of genes, chromosomes, and genetic variation in inheritance
  • Describe the process of meiosis and its importance in creating genetic diversity
  • Analyze patterns of inheritance, including Mendelian genetics and sex-linked traits
  • Apply principles of genetics to solve problems and interpret genetic data

Essential Ideas
  • Every living organism inherits a blueprint for life from its parents.
  • Chromosomes carry genes in a linear sequence that is shared by members of a species.
  • The inheritance of genes follows patterns.
  • Meiosis leads to independent assortment of chromosomes and unique composition of alleles in daughter cells.

Genes and the Human Genome Project
  • The Human Genome Project was an international scientific research project that aimed to determine the base pairs that make up human DNA and identify all the genes in the human genome.
  • The project was launched in 1990 and completed in 2003, successfully sequencing the approximately 3 billion base pairs that make up the human genome.
  • Using data from the Human Genome Project, scientists have estimated that the human genome contains anywhere from 20,000 to 25,000 genes.
  • The project provided researchers with basic information about the sequences of the three billion chemical base pairs (adenine, thymine, guanine, and cytosine) that make up human DNA.

Genetic Mutations and Disorders
  • Genetic mutations can lead to genetic disorders, such as sickle cell anemia.
  • Sickle cell anemia is used as an example of a genetic disorder caused by a mutation.
  • The Human Genome Project aimed to improve the understanding of genetic disorders and address the ethical, legal, and social implications that might arise from defining the entire human genomic sequence.
  • Nearly all human medical conditions, except physical injuries, are related to changes (mutations) in the structure and function of DNA, including heritable "Mendelian" diseases that result from mutations in a single gene.

Teacher Notes

Teacher can emphasize the transformative impact of the Human Genome Project and its connection to understanding genetic disorders like sickle cell anemia:

The Human Genome Project was a landmark scientific achievement that had a profound and lasting impact on our understanding of human genetics. By sequencing the entire human genome, consisting of over 3 billion base pairs, the project provided researchers with an unprecedented level of insight into the genetic makeup of our species.One key way the teacher can emphasize the significance of the HGP is by highlighting how it fundamentally changed the way we approach biological and medical research. Prior to the HGP, scientists had a fragmented and incomplete understanding of the human genome. The project's success in mapping the full sequence of our DNA laid the groundwork for a new era of genomic research and discovery.With this comprehensive genetic blueprint, scientists were able to start identifying the specific genes responsible for various biological functions and disease processes. This was a critical step in advancing our understanding of the genetic basis of human health and disease.The teacher can then draw a direct connection between the HGP's impact and our knowledge of genetic disorders like sickle cell anemia. Sickle cell anemia is caused by a specific mutation in the hemoglobin gene that results in abnormal red blood cells. Prior to the HGP, identifying the genetic underpinnings of such disorders was extremely challenging.

Structure and Function of Chromosome

Structure and Function of Chromosomes:

  • Chromosomes are the structures within cells that carry the genetic information in the form of genes.
  • Each human cell normally contains 23 pairs of chromosomes, for a total of 46 chromosomes.
  • Chromosomes are made up of DNA, which contains the instructions for the development and functioning of all living organisms.
  • Genes, the basic units of heredity, are located along the length of the chromosomes.
  • Chromosomes play a crucial role in ensuring the proper transmission of genetic information from one generation to the next.

Teacher Notes
  • Emphasize the fundamental role of chromosomes in carrying and transmitting the genetic information that defines an organism.
  • Explain how the DNA contained within chromosomes encodes the genes that determine an individual's traits and characteristics.
  • Highlight the importance of the 23 pairs of chromosomes in maintaining the normal genetic complement in human cells.

Chromosomes are the essential structures within cells that carry the genetic information in the form of DNA. Each human cell typically contains 23 pairs of chromosomes, for a total of 46 chromosomes. The DNA molecules contained within these chromosomes encode the genes that define an individual's unique traits and characteristics. Genes are the functional units of heredity, containing the instructions for the development and functioning of all living organisms.

The DNA that makes up chromosomes is tightly coiled and packaged around proteins called histones, allowing the lengthy genetic material to fit within the confines of the cell nucleus. This intricate packaging ensures the proper transmission of genetic information from one generation to the next during cell division.

The 23 pairs of chromosomes in human cells are crucial for maintaining the normal genetic complement. Each pair consists of one chromosome inherited from the mother and one from the father, ensuring that the full set of genetic instructions is present in every cell. Any abnormalities in the number or structure of chromosomes can lead to serious genetic disorders and diseases. For example, the presence of an extra copy of chromosome 21 results in Down syndrome. Maintaining the proper chromosome count and structure is essential for the healthy development and functioning of an organism.

In summary, chromosomes play a fundamental role in carrying and transmitting the genetic information that defines an individual. The DNA within chromosomes encodes the genes that determine a person's unique traits, and the 23 pairs of chromosomes are critical for preserving the normal genetic complement in human cells. Understanding the structure and function of chromosomes is essential for comprehending the biological basis of heredity and genetic disorders.

Karyotypes and Genome Size:
  • A karyotype is a visual representation of an individual's chromosomes, typically obtained through microscopic analysis of a cell sample.
  • Karyotyping involves staining the chromosomes and arranging them in order of size and shape to identify any abnormalities in number or structure.
  • Karyotype analysis can detect various chromosomal abnormalities, such as extra or missing chromosomes (aneuploidies), as well as structural changes like deletions, duplications, and translocations.
  • The human genome, which is the complete set of genetic information contained in human cells, is estimated to be approximately 3 billion base pairs in size

Teacher Notes

Karyotype analysis is a powerful cytogenetic technique that allows for the identification of chromosomal abnormalities, which can be associated with various genetic disorders and diseases. Here's a detailed explanation of how karyotyping works and its significance:

  1. The Process of Karyotyping:
    a. A sample of cells (e.g., from amniotic fluid, blood, or bone marrow) is collected and cultured in the laboratory to allow the cells to divide and produce metaphase chromosomes.
    b. The chromosomes are then treated with special stains that create a unique banding pattern along the length of each chromosome.
    c. The stained chromosomes are photographed under a microscope, and the images are cut out and arranged in pairs according to their size, centromere position, and banding pattern.
    d. This arranged set of chromosomes is called a karyotype, and it provides a visual representation of an individual's complete chromosome complement.
  2. Detection of Chromosomal Abnormalities:
    a. Numerical Abnormalities: Karyotyping can detect changes in the number of chromosomes, such as trisomies (an extra copy of a chromosome) or monosomies (a missing chromosome). For example, Down syndrome is caused by an extra copy of chromosome 21 (trisomy 21).
  3. b. Structural Abnormalities: Karyotyping can also identify structural changes in chromosomes, such as deletions (missing parts of a chromosome), duplications (extra copies of chromosome segments), inversions (reversed segments), and translocations (exchanges of material between chromosomes).
    c. These numerical and structural abnormalities can have significant impacts on gene expression and function, leading to various genetic disorders and diseases.
  4. Significance of the Human Genome Size and Mapping:
    a. The human genome is estimated to be approximately 3 billion base pairs in size, containing around 20,000-25,000 genes.
    b. The comprehensive mapping of the human genome through projects like the Human Genome Project (HGP) has revolutionized our understanding of human genetics.
    c. The HGP provided researchers with a complete blueprint of the human genetic code, enabling the identification of genes associated with specific traits, diseases, and disorders.
    d. This knowledge has paved the way for advancements in fields such as personalized medicine, genetic testing, and the development of targeted therapies for various genetic conditions.

  5. Karyotype analysis is a powerful tool because it allows for the direct visualization and identification of chromosomal abnormalities that can have profound effects on an individual's health and development. By combining karyotyping with the wealth of information provided by the Human Genome Project, researchers and clinicians can better understand the genetic basis of diseases and develop more effective diagnostic and therapeutic approaches.

     

Meiosis and Genetic Variation

Here is a detailed review of the meiosis process and how it creates genetic diversity:Meiosis is a specialized type of cell division that produces haploid gametes (egg and sperm cells) from diploid parent cells. It consists of two successive nuclear divisions, meiosis I and meiosis II, following a single round of DNA replication.Meiosis I:

  1. Prophase I:
    • Chromosomes condense and become visible as X-shaped structures.
    • Homologous chromosomes pair up and undergo synapsis, aligning gene-by-gene.
    • Crossing over occurs, where homologous chromosomes exchange genetic material, creating new combinations of alleles on each chromosome.
  2. Metaphase I:
    • The paired homologous chromosomes line up along the metaphase plate.
  3. Anaphase I:
      • Homologous chromosomes separate and move to opposite poles, resulting in a reduction of chromosome number from diploid to haploid.
    2. Telophase I:
      • Two haploid daughter cells form, each with half the original number of chromosomes.
    Meiosis II:
    5. Prophase II: No further DNA replication occurs.
    1. Metaphase II: Chromosomes line up individually.
    2. Anaphase II: Sister chromatids separate and move to opposite poles.
    3. Telophase II: Four haploid daughter cells form, each with a unique combination of chromosomes due to the independent assortment of chromosomes during meiosis I and crossing over.

Meiosis and the creation of genetic diversity

Meiosis creates genetic diversity in two main ways:

  1. Crossing over in prophase I leads to recombination of genetic material, producing new combinations of alleles on each chromosome.
  2. Independent assortment of chromosomes during meiosis I results in random distribution of maternal and paternal chromosomes into gametes, leading to unique genetic combinations in each gamete.

The fusion of two genetically distinct gametes during fertilization further increases genetic diversity in the offspring

Review of the meiosis process
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Cell Vocabulary

    Here are some key vocabulary terms that may be included in an MYP Cell Biology unit on Introduction to Cells:

    1. Cell - The basic unit of life, consisting of a cell membrane, cytoplasm, and genetic material.

    2. Cell membrane - The thin, flexible barrier that surrounds the cell and controls what enters and exits.

    3. Cytoplasm - The gel-like substance inside the cell that contains organelles and other cellular components.

    4. Organelles - Specialized structures within a cell that carry out specific functions, such as the nucleus, mitochondria, and ribosomes.

    5. Nucleus - The central organelle of a eukaryotic cell that contains genetic material.

    6. Mitochondria - Organelles that produce energy for the cell through cellular respiration.

    7. Ribosomes - Organelles that synthesize proteins.

    8. Prokaryotic cell - A type of cell that lacks a nucleus and membrane-bound organelles.

    9. Eukaryotic cell - A type of cell that has a nucleus and membrane-bound organelles.

    10. Cell theory - The scientific theory that all living organisms are made up of cells, and that cells are the basic unit of life.

    11. Tissue - A group of cells that work together to perform a specific function.

    12. Organ - A structure composed of multiple tissues that work together to perform a specific function.

    13. Organ system - A group of organs that work together to perform a specific function.

    14. Biotechnology - The use of living organisms or their components to develop useful products or processes.

    15. Microscope - An instrument used to observe small objects or organisms that are too small to be seen with the naked eye.

      Learning Activities
      • Observing and comparing different types of cells under a microscope
      • Researching and presenting on a particular type of cell and its function in the body
      • Creating models or diagrams to illustrate the structure and function of a cell
      • Writing a scientific report on the cell theory and its significance in modern biology
      • Conducting a debate on the ethics of using biotechnology to manipulate cells and organisms

      Unit Question

      What are cells and how do they function?

      Key Concepts

       Function, Connection, Structure

      Related concepts

      Cell Theory, Organelles, Types of Cells

      Inquiry
      • Plan and carry out an investigation to observe and compare the structure of different types of cells
      • Use appropriate scientific language and tools to make observations and gather data
      • Analyze and interpret data to draw conclusions about cell structure and function

      Knowledge and Understanding

       

      • Demonstrate knowledge and understanding of the structure and function of cells
      • Describe different types of cells and their organelles
      • Explain the cell theory and its significance

      Communication
      • Communicate scientific information effectively using appropriate scientific language and formats
      • Use diagrams and models to illustrate the structure and function of cells
      • Evaluate the credibility and reliability of scientific sources

      Attitudes

       Students should develop positive attitudes towards scientific inquiry and investigation, including curiosity, open-mindedness, and a willingness to engage in scientific discourse.

      Prokaryotic cells and eukaryotic cells are two main types of cells. The main differences between them are in terms of their structure and function.

      Prokaryotic cells

      Prokaryotic Cells

      Prokaryotic cells are typically smaller and simpler in structure, lacking a nucleus and other membrane-bound organelles. They are usually unicellular and can be found in a wide range of environments, including soil, water, and inside other organisms. Examples of prokaryotic cells include bacteria and archaea.

      There are two main types of prokaryotic cell, bacteria and archaea, which differ in their structure, habitat, and genetic material.

      Bacteria

      These are unicellular organisms that are found in a wide range of environments, including soil, water, and living organisms. Bacteria can have different shapes, including spherical (cocci), rod-shaped (bacilli), and spiral (spirilla). They have a cell wall that provides structure and protection, and their genetic material is located in the cytoplasm.

      Archaea

      These are unicellular organisms that are found in extreme environments, such as hot springs, salt flats, and deep sea vents. Archaea can have different shapes, including spherical, rod-shaped, and spiral. They also have a cell wall and their genetic material is located in the cytoplasm. However, the structure and composition of their cell wall and genetic material are different from bacteria.

      Prokaryotic

      Prokaryotes are organisms whose cells lack a nucleus

       

      • They belong to the kingdom Monera (i.e. bacteria)

      Prokaryotic cells share the following structures:

      •  A single, circular DNA molecule (genophore)

      •  A peptidoglycan cell wall and 70S ribosomes

      Prokaryotic cells may also contain the following:

      • Pili (for attachment or bacterial conjugation)

      • Flagella (a long whip-like tail for movement)

      • Plasmids (autonomous DNA molecules)

       

      Eukaryotic cells

      Eukaryotic Cells

      Eukaryotic cells are generally larger and more complex in structure, having a nucleus and other membrane-bound organelles that allow for more specialized functions. They can be unicellular or multicellular, and are found in a wide range of environments. Examples of eukaryotic cells include animal cells, plant cells, and fungal cells.

      Eukaryotic cells can be classified into different types based on their characteristics and the organisms they are found in.

       

      Animal Cells

      These are the cells found in plants. They have all the organelles found in animal cells, as well as a cell wall, chloroplasts, and a large central vacuole.

      Plant Cells

      These are the cells found in plants. They have all the organelles found in animal cells, as well as a cell wall, chloroplasts, and a large central vacuole.

      Fungi Cells

      These are the cells found in fungi. They have a cell wall made of chitin, a nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, and vacuoles.

      Protist cells:

      These are a diverse group of eukaryotic cells that are not classified as plants, animals, or fungi. They include single-celled organisms such as amoebas, paramecia, and algae, as well as multicellular organisms such as seaweed.

       

      Compare the Cell types

      Organelle Prokayotic Eukaryotic
      Nucleus Lack a nucleus Have a nucleus
      Organelles Lack membrane-bound organelles Have membrane-bound organelles
      Chromosomes Have a single, circular chromosome Have multiple, linear chromosomes
      Size Usually smaller Generally larger
      Cell Type Typically unicellular Can be unicellular or multicellular
      Environment Found in various environments (soil, water) Can be found in a wide range of environments
      Metabolic Can perform all necessary functions of life Have specialized organelles for more complex functions
      Reproduction Binary fission Mitosis and meiosis, and can undergo differentiation
      Genetic Transfer Can exchange genetic material through HGT Sexual reproduction and genetic recombination

      Organelles in a cell

      Nucleus

      The nucleus is the control center of the cell and contains the cell's genetic material (DNA). It is responsible for regulating gene expression and cell division.

      Mitochondria

      Mitochondria are the powerhouses of the cell. They produce energy in the form of ATP through the process of cellular respiration.

      Endoplasmic reticulum (ER):

       The ER is a network of membranes that is involved in protein synthesis, folding, and transport. There are two types of ER: smooth ER, which is involved in lipid synthesis, and rough ER, which is studded with ribosomes and is involved in protein synthesis.

      Golgi apparatus:

      The Golgi apparatus is involved in the modification, sorting, and packaging of proteins and lipids for transport to different parts of the cell or for secretion outside the cell.

       Lysosomes

       Lysosomes are membrane-bound organelles that contain enzymes responsible for breaking down and recycling cellular waste and debris.

      Ribosomes

       Ribosomes are responsible for protein synthesis. They are either free in the cytoplasm or attached to the rough ER.

      Cytoskeleton

      Student Guide

      Statement of Enquiry

      Understanding the structure and function of cells leads to innovative technological advances in medicine and biotechnology.

      Unit Title: Introduction to Cells

      Unit Question: What are cells and how do they function?

      Assessment Criteria
      1. Knowledge and understanding
      • Describe the structure and function of cells
      • Explain the cell theory and its significance
      • Identify different types of cells and their organelles

          2.  Investigating

      • Plan and carry out an investigation to observe and compare the structure of different types of cells
      • Use appropriate scientific language and tools to make observations and gather data
      • Analyze and interpret data to draw conclusions about cell structure and function

           3.Communication

      • Communicate scientific information effectively using appropriate scientific language and formats
      • Use diagrams and models to illustrate the structure and function of cells
      • Evaluate the credibility and reliability of scientific sources

       

      Key Concepts
      • Function
      • Connection
      • Structure

      Related Concepts
      • Cell Theory
      • Organelles
      • Types of Cells

      Global Context

      Scientific and Technical Innovation

      Introduction to Cells

       

      • Watch a video or read an article on the discovery of cells and the cell theory
      • Discuss the significance of the cell theory in modern biology
      • Complete a worksheet on the basic structure and function of cells

      Types of Cells

       

      • Research and present on a particular type of cell and its function in the body
      • Compare and contrast prokaryotic and eukaryotic cells
      • Use a microscope to observe and compare different types of cells

      Organelles and types of cells
        • Create a model or diagram of a cell and its organelles
        • Investigate the function of organelles such as the nucleus, mitochondria, and ribosomes
        • Conduct an experiment to observe the process of cellular respiration

        Application of cell biology
        • Research and present on a current application of cell biology, such as stem cell research or genetic engineering
        • Conduct a debate on the ethics of using biotechnology to manipulate cells and organisms
        • Write a reflection on the significance of understanding cell biology in modern society

         

        Assessment
        1. Quiz on the basic structure and function of cells
        2. Investigation report on comparing the structure of different types of cells
        3. Scientific report on the function of a particular organelle
        4. Presentation on a current application of cell biology
        5. Reflective essay on the significance of understanding cell biology

         

        Knowledge Check

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