11.3 Section Objectives – page 296

1. Using the table on Pg. 292, write the amino acid sequence that would be made according to the codons on the mRNA chain. • Why do you think this exact base sequence is important?

2. 11.3 Section Objectives – page 296 Section Objectives: • Categorize the different kinds of mutations that can occur in DNA. • Compare the effects of different kinds of mutations on cells and organisms.

3. 11.3 Section Summary 6.3 – pages 296 - 301 Mutations • Any change in DNA sequence is called a mutation. • Mutations can be caused by errors in replication, transcription, cell division, or by external agents.

4. 11.3 Section Summary 6.3 – pages 296 - 301 Mutations that can be passed on • Mutations can affect the reproductive cells of an organism by changing the sequence of nucleotides within a gene in a sperm or an egg cell. • If this cell takes part in fertilization, the altered gene would become part of the genetic makeup of the offspring.

5. Mutations in reproductive cells 11.3 Section Summary 6.3 – pages 296 - 301 • A mutation may produce a new trait or it may result in a protein that does not work correctly. • Sometimes, the mutation results in a protein that is nonfunctional, and the embryo may not survive. • In some rare cases a gene mutation may have positive effects.

6. 11.3 Section Summary 6.3 – pages 296 - 301 Mutations in body cells • What happens if powerful radiation hits the DNA of a nonreproductive cell, a cell of the body such as in skin, muscle, or bone? • If a body cell’s DNA is changed, this mutation would not be passed on to offspring. • However, the mutation may cause problems for the individual.

7. 11.3 Section Summary 6.3 – pages 296 - 301 Mutations in body cells • Damage to a gene may impair the function of the cell. • When that cell divides, the new cells also will have the same mutation. • Some mutations of DNA in body cells affect genes that control cell division. • This can result in the cells growing and dividing rapidly, producing cancer.

8. Types of Mutations 11.3 Section Summary 6.3 – pages 296 - 301 • A point mutation is a change in a single base pair in DNA. THE DOG BIT THE CAT. THE DOG BIT THE CAR. • A change in a single nitrogenous base can change the entire structure of a protein because a change in a single amino acid can affect the shape of the protein.

9. 11.3 Section Summary 6.3 – pages 296 - 301 mRNA Normal Protein Stop Replace G with A Point mutation mRNA Protein Stop

10. An example of a point mutation, is sickle-cell disease. 11.3 Section Summary 6.3 – pages 296 - 301 • Sickle-cell diseases cause the red blood cells to be deformed. The result is that they get stuck in the blood vessels, depriving tissues of oxygen, causing strokes, and blood clots.

11. Types of Mutations 11.3 Section Summary 6.3 – pages 296 - 301 A point mutation takes place when a single nitrogenous base (letter) is changed at one point. THE DOG BIT THE CAT. THE DOG BIT THE CAR. What would happen if a single nitrogenous base (letter) is deleted? THE DOG BIT THE CAT. THDOGB ITT HEC AT.

12. Types of Mutations 11.3 Section Summary 6.3 – pages 296 - 301 • A mutation in which a single base is added or deleted from DNA is called a frameshift mutation because it shifts the reading of codons by one base. Deletion of U

13. Types of Mutations 11.3 Section Summary 6.3 – pages 296 - 301 • The new sequence with the deleted base would be transcribed into mRNA. • But then, the mRNA would be out of position by one base. • This mutation would cause nearly every amino acid in the protein after the deletion to be changed. Deletion of U

14. 11.3 Section Summary 6.3 – pages 296 - 301 Frameshift mutations • Frameshift mutations can cause severe genetic diseases like Cystic Fibrosis and Lou Gehrig’s Disease. • Lou Gehrig’s Disease is a progressive neurological disease. Affects nerve cells used for voluntary muscle control

15. Lou Gehrig’s Disease, or Amyotrophic Lateral Sclerosis (ALS) is caused by a frameshift mutation on chromosome 21. With ALS, there is a deletion of a Cytosine on this gene. Every other base moves down, making all the amino acids incorrect after that. Human Karyotype

16. Cystic Fibrosis Section 12.1 Summary – pages 309 - 314 • Cystic fibrosis (CF) is one of the most common fatal genetic disorders among Americans. • It affects the lungs and digestive tract • Due to a defective protein in the plasma membrane, cystic fibrosis results in the formation and accumulation of thick mucus in the lungs and digestive tract.

17. Cystic Fibrosis is caused by a frameshift mutation on chromosome 7. Three nitrogenous bases are deleted to cause this mutation in the amino acid sequence.

18. Chromosomal Alterations 11.3 Section Summary 6.3 – pages 296 - 301 • Changes may occur in chromosomes as well as in genes. • Sometimes during mitosis or meiosis chromosomes break and then rejoin incorrectly, or just a piece breaks off for good. • Structural changes in chromosomes are called chromosomal mutations.

19. Causes of Mutations 11.3 Section Summary 6.3 – pages 296 - 301 • Some mutations seem to just happen, perhaps as a mistake in base pairing during DNA replication. • These mutations are said to be spontaneous. • However, many mutations are caused by factors in the environment, such as radiation, chemicals, and even high temperatures. • Any agent that can cause a change in DNA is called a mutagen.

20. Repairing DNA 11.3 Section Summary 6.3 – pages 296 - 301 • Enzymes proofread the DNA and replace incorrect nucleotides with correct nucleotides. • These repair mechanisms work extremely well, but they are not perfect. • The greater the exposure to a mutagen such as UV light, the more likely is the chance that a mistake will not be corrected.

21. Section 3 Check Question 1 Any change in DNA sequences is called a _______. A. replication B. mutation C. transcription D. translation The answer is B.

22. Section 3 Check Question 2 Which is more serious, a point mutation or a frameshift mutation? Why? Answer A frameshift mutation is more serious than a point mutation because it disrupts more codons than a point mutation.

23. Section 3 Check Question 3 Why are chromosomal mutations rarely passed on to the next generation? Answer Few chromosomal changes are passed on to the next generation because the zygote usually dies. If the zygote survives, it is often sterile and incapable of producing offspring.