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Do Now: What is a gene? A sequence of nucleotides

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1 Do Now: What is a gene? A sequence of nucleotides A specific sequence of nucleotides A sequence that codes for a polypeptide Composed of DNA Determines the phenotype of the individual Located on a chromosome Structure which is inherited and passed on The specific sequence (gene) should not be changed. Why? The sequences the information that determines the order of amino acids. If the order of amino acids is changed the polypeptide is altered and may lose its function.

2 Mutations What do they change and what effect do they have on the organisms and a population?

3 Gene Mutation A change in the DNA
A change in the sequence of nitrogenous bases: A, T, C or G Mutagens change DNA; carcinogens cause cancer

4 Follow the instruction of your teacher
Lab #1 Gene Mutation Groups of 2 Each member of the group completes a Gene Mutation lab sheet, legibly and coherent. Must be completed in 15 minutes and then With your partner, answer the questions. Follow the instruction of your teacher

5 Answers to selected lab questions
Answers to selected lab questions. Correct responses use the terms amino acid, polypeptide , translation correctly. The lab questions are really about how a mutation affects the polypeptide. When you read the sequences, you were the ribosome translated the altered mRNA. 2. Results of a mutation vary; they don’t produce the same results. Addition and deletion are most drastic. 6a. A stop codon at the beginning of a gene would prevent the polypeptide from being made, no translation. 6b. If a start codon is omitted at the beginning of a gene, the polypeptide would not begin to be synthesized. 6c. If a stop codon is in the middle of a gene, the polypeptide chain would be shortened & translation would be terminated sooner that should. Addition and deletion shift the reading frame of the mRNA which results in the change in kind and number of amino acids, thus altering the polypeptide greatly from the original. If the base codes creates a codon that codes for the same amino acid. This is called a silent mutation.

6 For each, compare the original and mutated strands of DNA
The next few slides are illustrations of the mutations you simulated in the lab today. Brings out a mutation. How? Translation For each, compare the original and mutated strands of DNA

7 Frameshift Mutation: Deletion

8 Frameshift Mutation: Insertion

9 Point Mutation: Nonsense Mutation
Can you describe what effect the mutation has?

10 Point Mutation: Missense Mutation
Can you describe what effect the mutation has?

11 Mutation comparison

12 More Mutations… Slide is only for the diehard Mutation student

13 Categories of Gene Mutation:
Point Frameshift Results from inserting or deleting one or more nucleotides Changes the “reading frame” like changing a sentence Usually alters the structure of the polypeptide Results changing one nucleotide and replacing it with a different one Changes the “codon” which may substitute a different amino acid Usually alters the structure of the polypeptide Let’s explore a real life example

14 What is controlling making sickle shaped cells?
Have only round genes Have both round & sickle genes Human Blood Smears: red blood & white blood cells Person #1 (left side): Phenotype is all round RBC’s Person #2 (right side): Phenotype is round and sickled shape RBC’s Which person does not have the disease? Why What is controlling making sickle shaped cells? Another form of the gene. What gave rise to the new form?

15 Video Lab #2: The Genetic Code A real life example illustrating the relationship between DNA, the gene and the protein: Sickle Cell Anemia

16 Video Questions: Hemoglobin is a transport protein. How many polypeptide chains make up one hemoglobin molecule? What important respiratory gas is transported by hemoglobin? How was the gene to synthesize hemoglobin mutated? What type is this? Because a mutation has altered, what can the hemoglobin protein no longer do? Can you summarize how protein synthesis occurs? Can you explain how protein synthesis allows an organism to function and be well? Can you explain what causes an inherited disease?

17 Point Mutation Sickle Cell disease is the result of one nucleotide substitution Occurs in the hemoglobin gene Sickle Cell is inherited so it can be passed on. The gene is found in all cells, specifically reproductive cells. Round cells have genes that make the properly formed polypeptides (proteins) and the sickle shaped gene makes the hemoglobin with the wrong shape.

18 Human Red Blood Cells Contain the protein, hemoglobin (Hb)
O2 binds to Hb = oxygenated blood Red Blood Cells are doughnut shaped cells What give the RBC’s its round shape? Explain what caused sickle shaped RBC to How does structure relate to function of a appear? protein?

19 Sickle Cell Anemia RBC’s are “sickled shape”
Hemoglobin protein has been altered -shape has changed Cells stick to each other; Oxygen binding capacity has been altered. Circulatory problems arise because the sickle cells stick together.

20 Valine-Histidine-Leucine-Threonine-Proline-Glutamic Acid-Glutamic Acid
Normal Hemoglobin: Valine-Histidine-Leucine-Threonine-Proline-Glutamic Acid-Glutamic Acid Abnormal Hemoglobin: Valine-Histidine-LeucineThreonine-Proline-Valine-Glutamic Acid Sickle Cell Anemia had change in the polypeptide chain: Glutamic acid is changed to Valine Why??????? How can this be??????????????

21 Mutation Changes Codon
Sickle Hb DNA = CAT mRNA = GUA = Valine -Proline-Valine-Glutamic Acid- This results from mutated DNA! Normal Hb DNA = CTT mRNA = GAA = Glutamic acid -Proline-Glutamic Acid-Glutamic Acid- Base-pair substitution = replacement of one nitrogenous base This is also referred to as a point mutation.

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