Unit 3 B Structure and Function of Molecular

Unit 3 B: Structure and Function of Molecular Genetics SB 2. Obtain, evaluate, and communicate information to analyze how genetic information is expressed in cells. a. Construct an explanation of how the structures of DNA and RNA lead to the expression of information within the cell via the processes of replication, transcription, and translation. Learning Targets: 3. 10 I can compare and contrast the structure of DNA and RNA 3. 11 I can describe the structure and roles of the three types of RNA. 3. 12 I can describe the process of transcription and transcribe an m. RNA strand from DNA. 3. 13 I can describe the process of translation (protein synthesis) including determining the amino acid sequence coded for by an m. RNA strand. 3. 14 I can explain the role of enzymes in the process of transcription and translation. 3. 15 I can explain the role of ribosomes in protein synthesis 3. 16 I can construct an argument to support the claim that gene mutations can cause the creation of new or defective proteins.

Structure of RNA • RNA (ribonucleic acid) is a nucleic acid composed of four types of nucleotides • Made up of single chain of nucleotides • Each nucleotide has three parts: – Phosphate group – Ribose sugar – Nitrogen-containing base • Adenine – Uracil • Cytosine - Guanine

Function of RNA • RNA carries DNA’s instructions • Molecule that is responsible for transmitting the DNA code into proteins • Essential for protein synthesis • Located inside the nucleus, in the cytoplasm, and at the ribosome

Types of RNA • There are three types of RNA. – Messenger RNA (m. RNA) • carries the message that will be translated to form a protein • Like the mailman – Ribosomal RNA (r. RNA) • forms part of the ribosome where proteins are made – Transfer RNA (t. RNA) • brings amino acids from the cytoplasm to ribosome.

Using the pictures below identify: 3 differences and 2 similarities between DNA and RNA

Complete the chart Comparing the structure of DNA and RNA DNA RNA _____ strand of nucleotides ______ sugar Contains bases: _______, _______, _______

Recap • RNA differs from DNA in three major ways: – RNA has ribose sugar – RNA has uracil instead of thymine – RNA is a single stranded structure

Review: Role of DNA Central Dogma of Biology • The central dogma includes three process. – Replication – Transcription – Translation replication transcription translation

Transcription • Transcription converts a gene into a single stranded RNA molecule. DNA RNA Can you remember the 3 differences between DNA and RNA?

Transcription • RNA carries the DNA’s instructions for protein synthesis. • The central dogma states that information flows in one direction from DNA to RNA to proteins. • RNA is the link between DNA and proteins. replication transcription translation

Transcription • Transcription is catalyzed by RNA polymerase • RNA polymerase helps recognize the start gene and unwinds a segment of DNA. Enzyme Recall start site transcription complex nucleotides

Transcription • Nucleotides pair with one strand of the DNA • RNA polymerase bonds the nucleotides together • The DNA helix winds back as the gene is transcribed. DNA

Transcription • The RNA strand detaches from the DNA once the gene is transcribed. RNA

Let’s Practice… If the DNA sequence had the nucleotides AGCCTA what would be the nucleotide sequence of the complementary DNA and the complementary RNA strand? What process creates DNA? What process creates RNA?

Translation • Translation is the last processes involved in protein synthesis. • Translation converts an m. RNA message into a protein, or polypeptide. • This process consists of three repeating steps. m. RNA Protein

Translation • Amino acids are coded by m. RNA base sequences. • Translation converts m. RNA message into proteins by decoding the base sequence. • A codon (m. RNA) is a sequence of three nucleotides that codes for a specific amino acid.

Translation • The genetic code matches each codon (m. RNA) to its amino acid or function. – Three stop codons • UGA, UAG – One start codon, codes for methionine. • AUG

The genetic code matches each m. RNA Codon with its amino acid or function

Translation • A change in the order in which codons (m. RNA) are read changes the resulting protein. • Regardless of the organism, codons code for the same amino acids – Unity of life

Translation • Amino acids are linked to become a protein or polypeptide. • An anticodon (t. RNA) is a set of three nucleotides that is complementary to a codon (m. RNA). • An anticodon is carried by a t. RNA

Translation For translation to begin: 1. anticodon (t. RNA) binds to its complementary start codon (m. RNA) and signals the ribosome to assemble. The complementary t. RNA bring its specific amino acid to the ribosome.

Translation 2. The ribosome helps form a polypeptide bond between the amino acids. The ribosome pulls the m. RNA strand the length of one codon.

Translation 3. The now empty t. RNA molecule exits the ribosome. The next complementary t. RNA (anticodon) molecule binds to the next exposed m. RNA (codon). – Processes are repeated for each codon (m. RNA). • Once the stop codon is reached, the ribosome releases the protein and disables.

Gene Expression When a gene (segment) of DNA code is used to build a protein, scientists say that gene has been expressed.

Let’s Practice… Put the following in order as they would occur in protein synthesis. A. B. C. D. E. Transcription of m. RNA in the nucleus of the cell. The ribosome helps form a polypeptide bond between amino acids The codon (m. RNA) and the complementary anticodon (t. RNA) bringing the specific amino acid to the ribosome. The now empty t. RNA leaves the ribosome and the process is repeated for each codon until the stop codon is reached. The polypeptide is released from the ribosome

Think Together… What would happen to the protein formed during translation if m. RNA was copied incorrectly?

Recall: Gene Mutations • Error in the sequence of nitrogen bases in a single gene – Remember: Codon (sequence of 3 nitrogen bases) corresponds to a particular amino acid • Two types of Gene Mutations: – Point mutation – Frame shift mutation

Gene Mutation Point Mutation • Change in a single base is called a point mutation • Each of these words represents different amino acid. THE CAT ATE THE RAT • Now what would happen if you changed one letter? THE CAT ATE THE BAT • Still makes sense but the meaning is different – Effects are usually minimal if any at all • Example: Sickle Cell – GAG codon is changed to GTG – Inserts wrong amino acid • How does this affect the resulting protein?

Gene Mutations • A point mutation substitutes on nucleotide for another. – Also known as substitution. Mutated Base

Gene Mutation: Frameshift Mutation • Base is added/deleted is called a Frameshift mutation THE CAT ATE THE RAT Deleted one base (deletion mutation): C THE ATA TET HER AT_ Added one base (insertion mutation): C THE CCA TAT ETH ERA T • The statement makes no sense and the meaning is completely different – Effects on the amino acid sequence are much more severe than a point mutation – Codon for different amino acid – The entire sequence of amino acid following the mutation are wrong

Wasting Syndrome • Gene mutation that results in the mutated form of myostatin protein. • Leads to overproduction of muscle tissue • Often seen in Belgian Blue and Piedmontese breeds of cattle

Resulting Mutations • Gene mutations can be one of three types depending on the nucleotide affected. – A silent mutation is one with no noticeable change. • Likely caused by a substitution of a base that codes for the same codon. – EX. UCU is replaced by UCC Both codons code for the amino acid serine. – In a missense mutation, the new nucleotide alters the codon affecting the sequence of amino acids and possible shape and function of the protein. – A nonsense mutation generates a stop codon.

SB 2. Obtain, evaluate, and communicate information to analyze how genetic information is expressed in cells. c. Ask questions to gather and communicate information about the use and ethical considerations of biotechnology in forensics, medicine, and agriculture. Learning Targets: 3. 16 I can construct an argument to support the claim that gene mutations can cause the creation of new or defective proteins. 3. 17 I can explain how biotechnology is used in forensics. 3. 18 I can explain how biotechnology is used in agriculture. 3. 19 I can explain how biotechnology is used in medicine. 3. 20 I can gather and evaluate evidence about the use and ethical considerations of biotechnology in forensics, medicine, and agriculture to develop an informed opinion.

Human Genome Project • Project that has identified all human genes, especially those associated with diseases • Human DNA consists of 3 billion base pairs – Contain 20, 000 -25, 000 genes • 2 -3 times as many genes as a worm or fruit fly. • Approximately 3% of DNA contains the information to make proteins. • Led to a greater understanding of genes themselves. – Has important implications to understanding human biology and what goes wrong in disease states. – Help us define disease states and predict possible candidates who are likely to suffer from a disease based on their nucleotide sequences.

Did you know… • DNA base pairs are the “meat” of the Human Genome Project – A huge database that was started to identify all human genes. • It is used to find diseases and even some potential parents have their genes searched for bad base pairs.

DNA technology • Manipulation of DNA to change or enhance characteristics of an organism • Use frequently in biotechnology

Genetic Engineering • Process in which genes, or pieces of DNA, are taken from one organism and transferred to another organism • Possible because all organisms share a similar genetic code • Makes recombinant DNA – DNA from two different organisms join together • Example: Plasmid – Produce medicine

Cloning • Process in which genetically identical individuals are created from a single cell • Scientist can take a single cell from an individual and grow it into an entirely new organisms that is genetically identical • Type of “asexual” reproduction

Cloning • Cloning – A genetic identical of an organism – First organism cloned in 1997—sheep called Dolly – DNA from an existing organism is inserted into an empty egg and allowed to reproduce

DNA Technology: Forensics Gel Electrophoresis • Technique used to analyze DNA by sorting DNA fragments according to their repose to an electrical field • The pattern that results from this process is called DNA fingerprint

DNA Technology: Forensics Gel Electrophoresis • Can be used to determine paternity • Identifying individuals in criminal and civil proceedings.

• • DNA Technology: Forensics DNA Fingerprint Gel Electrophoresis A DNA fingerprint is the pattern produced when DNA fragments are separated based on size by gel electrophoresis The more similar the DNA fingerprints of two organisms, the closer related they are. Law enforcement uses DNA fingerprints to identify suspects. Place DNA fingerprints from a known person with DNA fingerprints found at the scene of the crime – If the DNA fingerprints match, the person can be placed at the scene of the crime.

DNA Technology: AGRICULTURE • Use of organisms or their products to improve human health and food production • Genetically modified organisms (GMO) – enabling plants to produce new proteins • Protect crops from insects: BT corn – corn produces a bacterial toxin that kills corn borer (caterpillar pest of corn) • Extend growing season: fishberries – strawberries with an anti-freezing gene from flounder

Pros of GM Foods Produce higher yields Lower food costs Reduce land use Reduce chemical usage Reduce energy consumption After more than a decade, no evidence of harm has been found.

Cons of GM Foods No long-term studies Herbicide resistance genes may lead to overuse of herbicides. Insect resistance genes may threaten beneficial insects. Patents may prove too costly for small farmers.

DNA Technology: AGRICULTURE Transgenic Organisms – Inserting genes from one organisms into another The World Heath Organization estimates that between 1 and 2 million children die each year from vitamin A deficiency. • Golden rice is a genetically modified food that is fortified with beta carotene, which the human body converts into vitamin A. • This transgenic organism is the result of mixing genes from a bacterium and from daffodils into the rice genome. • It is not currently used due to regulatory issues. – Do you think we should be able to use it?

DNA Technology: AGRICULTURE Safety of Transgenics In the U. S. , current federal regulations treat GM foods and non-GM foods equally. No additional labeling is required to identify a product as genetically modified unless its ingredients are significantly different from its conventional counterpart. The possibility that meat from GM animals may soon enter the food supply has heightened concerns about labeling. As a result, some states have begun to consider legislation to require the labeling of GM foods. • Which argument do you find more convincing, the argument for GM foods or the argument against? • Would you be concerned if you found out that some of the food you eat regularly is genetically modified? • Do you think farmers and food manufacturers should have to label their products if they are genetically modified?

Ethics of the New Biology • What is the single most important ethical issue related to biotechnology? • Why does this issue need to be resolved?