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Unit VI Structure and Function of DNARNA Teaching Module B-4

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Unit VI Structure and Function of DNARNA Teaching Module B-4

    Unit VI Structure and Function of DNA/RNA Teaching Module B-4.1

Instructional Focus

    Compare DNA and RNA in terms of structure, nucleotides, and base pairs.

Content Overview for Module B-4.1

There are two types of nucleic acids.

    ? Deoxyribonucleic acid (DNA)

    ? Ribonucleic acid (RNA)

Both DNA and RNA are composed of small units called nucleotides. The

    nucleotides that compose nucleic acids have three parts:

    ? A nitrogenous base

     Cytosine (C)

     Guanine (G)

     Adenine (A)

     Thymine (T) (DNA only)

     Uracil (U) (RNA only)

    ? A simple (pentose) sugar

     Deoxyribose (DNA only)

     Ribose (RNA only)

    ? A phosphate group

The basic structure of the two molecules is different.

     DNA consists of two single chains which spiral around an imaginary axis to form

    a double helix with nitrogenous bases from each strand of DNA chemically

    bonded through the axis of the helix.

    ? When the nitrogenous bases of two strands of DNA chemically bond through

    the center of the helix, each base can bond to only one type of base. Bases

    that bond are called complementary bases.

     Guanine (G) and Cytosine (C) will only bond with each other.

     Thymine (T) and Adenine (A) will only bond with each other.

    1 Unit VI Structure and Function of DNA/RNA 3 7-1-10 S Curriculum

Content Overview for Module B-4.1

     RNA consists of a single chain of nucleotides with nitrogenous bases exposed

    along the side.

    ? When the nitrogenous bases of RNA chemically bond to a strand of DNA,

    each RNA base can bond with only one type of DNA base. Bases that bond

    are called complementary bases.

     Guanine (G) and Cytosine (C) will only bond with each other.

     Thymine (T) and Adenine (A) will only bond with each other. It is

    essential for students to compare the structure of the two types of

    nucleic acids.

     DNA RNA

    Cytosine (C) Cytosine(C) Type of base composing Adenine (A) Adenine (A) nucleotides Guanine (G) Guanine (G) Thymine(T) Uracil (U) Type of sugar composing deoxyribose ribose nucleotides

     Molecule structure and shape Double helix Single chain

Instructional Progression

Previous and future knowledge

This concept has not been addressed in previous grades.

Instructional Considerations

It is essential for students to understand that nucleic acids are organic

    molecules that serve as the blueprint for proteins and, through the action of proteins, for all cellular activity.

It is not essential for students to understand

     the chemical formula for DNA or RNA;

     the difference between pyrimidine bases and purine bases.

Key Vocabulary and Concepts

    Nucleic acids: deoxyribonucleic acid (DNA), ribonucleic acid (RNA) Nucleotides: nitrogenous base, sugar, phosphate group Complementary bases

    2 Unit VI Structure and Function of DNA/RNA 3 7-1-10 S Curriculum

Materials Needed

See Instructional Planning Guide Activity and Appendix I.

Suggested Teaching Module B-4.1

Revised Taxonomy: 2.6-B Understand Conceptual Knowledge

Introduction

    This module can be introduced by discussing the structural make up of DNA and RNA. It is important to explain the difference between DNA and RNA. RNA consists of a single chain of nucleotides, ribose and it is single stranded whereas DNA is double stranded and has deoxyribose as a sugar. There are four nitrogenous bases in DNA Adenine, Thymine, Guanine and Cytosine. RNA also consists of four nitrogenous bases Adenine, Uracil, Guanine and Cytosine. Uracil replaces Thymine in RNA. It is important for students to be able to pair nitrogenous bases with complimentary structures. A recommended website entitled “Compare DNA and RNA in Structural Basis (http://www.dnatube.com/video/1017/Compare-DNA-

    and-RNA-in-structural-basis), as well as, “DNA Structure”

    (http://www.sumanasinc.com/webcontent/animations/content/DNA_structure.html)

    can serve as a foundation animating the structure of DNA. This can be followed by using Building RNA and DNA (Instructional Planning Activity Guide B-4.1a, p12 ). After using this activity, the students should complete Comparing DNA and RNA (Instructional Planning Activity B-4.1b, p 15) and/or the follow-up questions found in DNA-RNA (Instructional Planning Activity Guide B-4.1c. p 17). Modeling DNA (http://www.kidsknowit.com/interactive-educational-movies/free-online-movies.php?movie=DNA is a website that can be used to bring closure to module B-4.1. It is important that the students are able to recognize, differentiate and interpret a DNA and RNA nucleotide.

Suggested Resources

See Instructional Planning Guide Activity and Appendix I.

    3 Unit VI Structure and Function of DNA/RNA 3 7-1-10 S Curriculum

Assessing Module B-4.1

Formative and Summative assessments

    The objective of this indicator is to compare DNA and RNA in terms of structure, nucleotides and base pairs; therefore, the primary focus of assessment should be to detect similarities and differences between structure of DNA and RNA, the nucleotides that compose DNA and RNA, and the bases that bond to form DNA and RNA.

In addition to compare, assessments may require students to

     recognize the chemical names of the DNA and RNA molecules;

     identify the parts of a nucleotide;

     recognize the names of the 5 bases and the two sugars that compose the

    nucleotides that make up all nucleic acids;

     interpret an illustration of a nucleotide;

     interpret an illustration of a DNA or an RNA molecule.

    4 Unit VI Structure and Function of DNA/RNA 3 7-1-10 S Curriculum

    Unit VI Structure and Function of DNA/RNA Teaching Module B-4.2:

Instructional Focus:

Summarize the relationship among DNA, genes and chromosomes

Content Overview for Module B-4.2

     A chromosome is a structure in the nucleus of a cell consisting essentially of one

    long thread of DNA that is tightly coiled.

     DNA, composed of nucleotides, provides the blueprint for the synthesis of

    proteins by the arrangement of nitrogenous bases.

    ? The code for a particular amino acid (the base unit of proteins) is determined

    by a sequence of three base pairs on the DNA molecule.

     A gene is a specific location on a chromosome, consisting of a segment of DNA,

    that codes for a particular protein.

    ? The particular proteins coded by the DNA on the genes determine the

    characteristics of an organism.

    ? Each chromosome consists of hundreds of genes determining the many

    proteins for an individual organism.

Instructional Progression

Previous and future knowledge

     thIn 7 grade (7-2.5), students summarized how genetic information is passed from parent to offspring by using the terms genes, chromosomes, inherited traits, genotype, phenotype, dominant traits and recessive traits.

    5 Unit VI Structure and Function of DNA/RNA 3 7-1-10 S Curriculum

Instructional Considerations

It is essential for students to understand that DNA, genes and chromosomes

    compose the molecular basis of heredity.

    It is not essential for students to understand the history behind the discovery of DNA.

Key Vocabulary and Concepts

Chromosome, DNA, Gene

Materials Needed

See Instructional Planning Guide Activity and Appendix I.

Suggested Teaching Module B-4.2

Revised Taxonomy: 2.4-B Understand Conceptual Knowledge

Introduction

    Introduce the module by using the Comparison of DNA, Chromosomes and Genes video (http://videos.howstuffworks.com/hsw/6020-chromosomes-gens-and-dna-video.html) and/or the Chromosomes, Genes and DNA animation

    (http://www.johnkyrk.com/DNAreplication.html). These videos summarize the

    relationship between DNA, genes and chromosomes and demonstrate how genes and chromosomes function. Following the introduction, students should complete the Chromosome Packing worksheet (Instructional Planning Activity Guide B-4.2a, p 20) as an analysis of genes and chromosomes. Students should be able to compare DNA, genes, and chromosomes upon completion.

Suggested Resources

See Instructional Planning Guide Activity and Appendix I.

    6 Unit VI Structure and Function of DNA/RNA 3 7-1-10 S Curriculum

Assessing Module B-4.2

Formative and Summative assessments

    The objective of this indicator is to summarize the relationship among DNA, genes,

    and chromosomes; therefore, the primary focus of assessment should be to give major points about how DNA, genes and chromosomes are related.

In addition to summarize, assessments may require students to

     recall the basic structure of chromosomes and genes;

     illustrate or interpret an illustration of the relationship of a chromosome, DNA

    and genes using words or diagrams.

Extension

    Some students may need to have their vocabulary reinforced and additional work in conceptualizing the functions of DNA, genes and chromosomes. One way to accomplish this is to have them use a writing prompt such as the one listed in “What’s in Common?” (Instructional Planning Activity Guide B4.2b, p 22).

    7 Unit VI Structure and Function of DNA/RNA 3 7-1-10 S Curriculum

    Unit VI Structure and Function of DNA/RNA Teaching Module B-4.3

Instructional Focus:

    Explain how DNA functions as the code of life and the blueprint for proteins.

Content Overview for Module B-4.3

     The specificity of proteins is determined by the order of the nitrogenous bases

    found in DNA.

    ? In order to construct the specific proteins needed for each specific purpose,

    cells must have a blueprint that reveals the correct order of amino acids for

    each of the thousands of proteins found in an organism.

    ? A gene is a segment of DNA that codes for one particular protein.

Each cell in an organism’s body contains a complete set of chromosomes.

    ? The number of chromosomes varies with the type of organism. For example,

    humans have 23 pairs of chromosomes; dogs have 39 pairs; potatoes have

    24 pairs.

    ? One pair of chromosomes in an organism determines the sex (male, female)

    of the organism and are known as sex chromosomes. All other chromosomes

    are known as autosomal chromosomes, or autosomes.

    ? Cells (except for sex cells) contain one pair of each type of chromosome.

     Each pair consists of two chromosomes that have genes for the same

    proteins.

     One chromosome in each pair was inherited from the male parent and the

    other from the female parent. In this way, traits of parents are passed to

    offspring when the male and female gametes (sex cells) combine. For

    example, human cells have 46 chromosomes (23 pairs).

     Each chromosome consists of thousands of genes. This is because there are so

    many unique proteins that each organism needs to produce in order to live and

    survive.

    ? Organisms that are closely related may have genes that code for the same

    proteins that make the organisms similar. For example, all maple trees have

    many of the same genes.

    ? Each individual organism has unique characteristics and those unique

    characteristics arise because of the differences in the proteins that the

    organism produces.

    8 Unit VI Structure and Function of DNA/RNA 3 7-1-10 S Curriculum

Content Overview for Module B-4.3 cont.

    ? Organisms that are not closely related share fewer genes than organisms

    that are more closely related. For example, red maple trees share more

    genes with oak trees than with earthworms.

    DNA replication is facilitated by specific enzymes. The first enzyme unzips the two strands of DNA that compose the double helix, separating

    paired bases.

     Each base that is exposed can only bond to its complementary base.

     Guanine (G) and Cytosine (C) will only bond with each other.

     Thymine (T) and Adenine (A) will only bond with each other.

     Each of the separated strands serves as a template for the attachment of

    complementary bases, forming a new strand, identical to the one from which it

    was “unzipped”.

     The result, unless there are mutations, is two identical DNA molecules.

Instructional Progression

Previous and future knowledge

     thIn 7 grade (7-2.5), students summarized how genetic information is passed from parent to offspring by using the terms genes, chromosomes, inherited traits, genotype, phenotype, dominant traits, and recessive traits.

    9 Unit VI Structure and Function of DNA/RNA 3 7-1-10 S Curriculum

Instructional Considerations

It is essential for students to understand that the DNA, which comprises the

     chromosomes, is considered the “code of life” (genetic code) because it organism’s

    contains the code for each protein that the organism needs.

It is essential for students to understand that DNA can function as the code of

    life for protein synthesis or the process of DNA replication, which ensures that every new cell has identical DNA.

It is not essential for students to understand the specific chromosome

    numbers for organisms, except for humans; the names of the specific enzymes needed for replication.

Key Vocabulary and Concepts

    Genetic code: sex chromosomes, autosomal chromosomes (autosomes), DNA replication

Materials Needed

See Instructional Planning Guide Activity and Appendix I.

Suggested Teaching Module B-4.3

Revised Taxonomy: Understand Conceptual Knowledge 2.7-B

Introduction

    Begin the module with an introductory discussion on DNA as the code of life and the blueprint for proteins. Further student involvement can be fostered by using the “A DNA Replication” website

    (http://www.wiley.com/college/pratt/0471393878/student/animations/dna_repliaction/index.html) or the “DNA Replication Model Animation” website

    (http://www.courses.fas.harvard.edu/~biotext/animations/replication1.swf) which

    illustrate this concept. DNA replication practice and review may be accomplished using the “DNA Replication Activity at the PBS.org interactive website (http://www.pbs.org/wgbh/aso/tryit/dna/#). Once the concepts have been taught,

    The Double Helix (Instructional Planning Activity Guide B-4.3a, p 23) can be used as an extension and/or a reinforcement activity for the module. It is important that students are able to summarize the role of DNA as the code of life. Students should be able to describe the steps of replication and diagram a model of DNA.

    10 Unit VI Structure and Function of DNA/RNA 3 7-1-10 S Curriculum

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