Genes and Gene Technology Instructional Lesson for 7 th Grade Life Science By Shannon Reece

Table of Contents What Do Genes Look Like? What Do Genes Look Like? How are traits determined? How are traits determined? How are traits determined How are traits determined Nucleotides Nucleotides Nucleotides A Picture of DNA A Picture of DNA A Picture of DNA A Picture of DNA DNA Structure DNA Structure DNA Structure DNA Structure Making Copies of DNA Making Copies of DNA Making Copies of DNA Making Copies of DNA From Trait to Gene From Trait to Gene From Trait to Gene From Trait to Gene Exceptions to Mendels Principles Exceptions to Mendels Principles Exceptions to Mendels Principles Exceptions to Mendels Principles How DNA Works How DNA Works Genes and Proteins Genes and Proteins The Making of a Protein The Making of a Protein Changes in Genes Changes in Genes An Example of Substitution An Example of Substitution Genetic Counseling Genetic Counseling Designer Genes Designer Genes

How are traits determined? Use previous knowledge to complete the following. Use previous knowledge to complete the following. Traits are determined by ________ which are located on chromosomes. Traits are determined by ________ which are located on chromosomes. Chromosomes are made up of protein and _______. Chromosomes are made up of protein and _______. Which type of materials makes the genes? Which type of materials makes the genes? Genes DNA

Nucleotides The 4 Subunits of a DNA molecule The 4 Subunits of a DNA molecule Made of 3 different types of material Made of 3 different types of material Sugar Sugar Phosphate Phosphate Base Base Identical except for base (4 of them) Identical except for base (4 of them) Adenine Adenine Thymine Thymine Guanine Guanine Cytosine Cytosine

Nucleotide Bases Each base has a slightly different shape Each base has a slightly different shape Refer to by first letter of name (A,T,G,C) Refer to by first letter of name (A,T,G,C) Chargaffs Rules Chargaffs Rules 1950s – Biochemist Erwin Chargaff Found: 1950s – Biochemist Erwin Chargaff Found: Amount of Adenine always = Amount of Thymine Amount of Adenine always = Amount of Thymine Amount of Guanine always = Amount of Cytosine Amount of Guanine always = Amount of Cytosine How could this help determine DNAs structure? How could this help determine DNAs structure?

Nucleotides

Picture of DNA Additional Information about DNAs structure Additional Information about DNAs structure Rosalind Franklin created images of the molecule – Spiral shape Rosalind Franklin created images of the molecule – Spiral shape Used X-ray diffraction process Used X-ray diffraction process Watson and Crick used others work to create models = double helix Watson and Crick used others work to create models = double helix

DNA Structure Double Helix Double Helix 2 sides of ladder = alternating sugar and phosphate 2 sides of ladder = alternating sugar and phosphate The rungs of the ladder = pair of nucleotide bases The rungs of the ladder = pair of nucleotide bases A pairs with T A pairs with T G pairs with C G pairs with C How does this structure explain Chargoffs findings? How does this structure explain Chargoffs findings?

DNA Structure

Making Copies of DNA A pairs with T and G pairs with C therefore A pairs with T and G pairs with C therefore One side of DNA is complementary to the other. One side of DNA is complementary to the other. EX. A sequence ACCG always binds to TGGC. EX. A sequence ACCG always binds to TGGC. Allows for DNA to replicate. Allows for DNA to replicate. Observe DNA Replication Observe DNA ReplicationDNA ReplicationDNA Replication

DNA Check What would the complementary strand of DNA be for the following sequence of bases? ACCTAGTTG What would the complementary strand of DNA be for the following sequence of bases? ACCTAGTTG How many molecules of DNA are there when replication is complete? How many molecules of DNA are there when replication is complete? Are the new DNA molecules complementary or identical to the original DNA molecule? Are the new DNA molecules complementary or identical to the original DNA molecule?

From Trait to Gene Each gene consists of a string of bases Each gene consists of a string of bases The order of bases gives the cell information about each trait The order of bases gives the cell information about each trait DNA functions the same for all organisms DNA functions the same for all organisms

Exceptions to Mendels Principles Incomplete Dominance Incomplete Dominance One trait is not dominant over another One trait is not dominant over another Each allele has own degree of influence Each allele has own degree of influence EX. Snapdragon flower EX. Snapdragon flower White x red = pink White x red = pinkR1R1R2 R1R2 R2

Exceptions to Mendels Rules One gene can influence more than one trait One gene can influence more than one trait EX. White tiger EX. White tiger White fur caused by a single gene that also influences eye color (blue) White fur caused by a single gene that also influences eye color (blue)

Exceptions to Mendels Rules Many genes can influence 1 trait Many genes can influence 1 trait Ex. Traits such as hair,eye and skin color are controlled by many genes together Ex. Traits such as hair,eye and skin color are controlled by many genes together Several varieties of blue eyes Several varieties of blue eyes

Review – What do genes look like? List the 3 parts of a nucleotide. List the 3 parts of a nucleotide. Which bases pair together in a DNA molecule? Which bases pair together in a DNA molecule? What shape was suggested by Rosalind Franklins X-ray images? What shape was suggested by Rosalind Franklins X-ray images? If a sample of DNA were found to contain 20% adenine, what percentage of thymine would be in the sample? Why? If a sample of DNA were found to contain 20% adenine, what percentage of thymine would be in the sample? Why?

Genes and Proteins Groups of 3 bases on DNA code for a specific amino acid (aa) Groups of 3 bases on DNA code for a specific amino acid (aa) Ex. CCA code for aa proline Ex. CCA code for aa proline Proteins are made of strings of aas Proteins are made of strings of aas Therefore, genes are sets of instructions for making proteins. Therefore, genes are sets of instructions for making proteins.

The Making of a Protein Copy the section of the DNA strand containing a gene Copy the section of the DNA strand containing a gene Messenger molecule take information into the cytoplasm Messenger molecule take information into the cytoplasm mRNA is fed through ribosomes 3 bases at a time mRNA is fed through ribosomes 3 bases at a time Transfer molecule picks up specific aa and links to form protein Transfer molecule picks up specific aa and links to form proteinform proteinform protein

The Making of a Protein

Changes in Genes Mutations Deletion Base is left out Insertion Base added Substitution Wrong base in place Of correct one Most common Mutations occur when there is a change in the order of bases.

Substitution Example: Example: The DNA sequence GAA = glutamic acid The DNA sequence GAA = glutamic acid A mistake occurs and GTA occurs instead = valine A mistake occurs and GTA occurs instead = valine The results cause sickle cell anemia The results cause sickle cell anemia Disease that affects red blood cells Disease that affects red blood cells Rbc has distorted shape Rbc has distorted shape

Genetic Counseling Most hereditary disorders are recessive Most hereditary disorders are recessive Disease occurs when child inherits defective gene from both parents Disease occurs when child inherits defective gene from both parents Carriers have only one allele for the disease Carriers have only one allele for the disease May pass on disease to children w/o knowing May pass on disease to children w/o knowing Genetic counseling provides information to couples that want to have children but are worried about disease Genetic counseling provides information to couples that want to have children but are worried about disease Use a diagram called a pedigree Use a diagram called a pedigree

Pedigree Traces a trait through generations of a family Traces a trait through generations of a family Makes it possible to predict if a person is a carrier Makes it possible to predict if a person is a carrier Learn more about pedigrees Learn more about pedigreespedigrees

Designer Genes Selective breeding = mating organisms with desirable characteristics to produce a new breed Selective breeding = mating organisms with desirable characteristics to produce a new breed Now we can produce desired characteristics without breeding Now we can produce desired characteristics without breeding Manipulate individual genes = genetic engineering (transfer genes from one organism to another) Manipulate individual genes = genetic engineering (transfer genes from one organism to another)

Designer Genes Genetic Engineering is used to: Genetic Engineering is used to: Manufacture proteins Manufacture proteins Repair damaged genes Repair damaged genes Identify individuals who may carry Identify individuals who may carry an allele for a disease The tobacco plant above had the firefly gene inserted in its DNA. Those are the leaf veins that are glowing yellow. This tobacco plant has had the firefly gene inserted in its DNA. Those are the leaf veins that are glowing yellow.

How DNA Works List the three types of mutations. List the three types of mutations. What type of mutation causes sickle cell anemia? What type of mutation causes sickle cell anemia? How is genetic engineering different from selective breeding? How is genetic engineering different from selective breeding? Mutations can occur in sex cells or in body cells. In which cell type might a mutation be passed from generation to generation? Explain. Mutations can occur in sex cells or in body cells. In which cell type might a mutation be passed from generation to generation? Explain. How are proteins made. List the 4 steps. How are proteins made. List the 4 steps.

Solve the following Problem Click on the work pedigree below to link to a set of genetics problems. Click on the work pedigree below to link to a set of genetics problems. Answer the question and draw the pedigree on a sheet of paper. Answer the question and draw the pedigree on a sheet of paper. PEDIGREE

Bibliography Holt Science and Technology, Life Science, 2000 Holt Science and Technology, Life Science, fs.huntingdon.edu fs.huntingdon.edu