Turner College & Career High School  2016 Mutations Turner College & Career High School  2016

What Are Mutations? Changes in the nucleotide sequence of DNA. May occur in somatic cells (body, not egg or sperm) and are not usually passed to offspring. May occur in gametes (eggs & sperm) and be passed to offspring.

Are Mutations Helpful or Harmful? Mutations happen regularly. Almost all mutations are neutral. Chemicals & UV radiation cause mutations. Many mutations are repaired by enzymes.

Are Mutations Helpful or Harmful? Some type of skin cancers and leukemia result from somatic mutations. Some mutations may improve an organism’s survival (beneficial)

2 Types of Mutations

1 Chromosome Mutations Caused by variations in: The structure of a chromosome. The loss or gain of part of a chromosome. The number of chromosomes.

1 Chromosome Mutations Five types exist: Deletion Inversion Translocation Nondisjunction Duplication

1 Deletion Due to breakage. A piece of a chromosome is lost.

1 Inversion Chromosome segment breaks off. Segment flips around backwards. Segment reattaches.

1 Duplication Occurs when a gene sequence is repeated.

1 Translocation Involves two chromosomes that aren’t homologous. Part of one chromosome is transferred to another chromosome.

1 Nondisjunction Failure of chromosomes to separate during meiosis. Causes gamete to have too many or too few chromosomes. Some Disorders: Down Syndrome: three 21st chromosomes. Turner Syndrome: single X chromosome.

Chromosome Mutation Animation 1 Chromosome Mutation Animation

2 Gene Mutations Change in the nucleotide sequence of a gene. May only involve a single nucleotide. May be due to copying errors, chemicals, viruses, etc.

Types of Gene Mutations 2 Types of Gene Mutations Include: Point Mutations Substitutions Insertions Deletions Frameshift

2 Point Mutation Change of a single nucleotide. Includes the deletion, insertion, or substitution of ONE nucleotide in a gene.

2 Point Mutation Sickle Cell disease is the result of one nucleotide substitution. Occurs in the hemoglobin gene.

2 Frameshift Mutation Inserting or deleting one or more nucleotides. Changes the “reading frame” like changing a sentence. Proteins built incorrectly. Original: The fat cat ate the wee rat. Frame Shift (“a” inserted): The fat caa tat eth ewe era t. Frame Shift (“a” deleted): The fat cta tet hew eer at.

Gene Mutation Animation 2 Gene Mutation Animation

Significance of Genetic Mutations A mutation can allow for an individual to have an advantage over other members of the species. A mutation could make an individual more camouflaged to avoid predators, faster to catch prey, or even better equipped to utilize nutrients. At the same time, some mutations can be a harmful to individuals, as is the case with genetic disorders Mutations in an individual organism can either help or hurt the chance that the individuals' genes will be passed on to offspring.

Mutation Classifications Gene mutations can be classified in two major ways: Hereditary mutations are inherited from a parent and are present throughout a person’s life in virtually every cell in the body. If the parent DNA has a mutation, the child that grows from the fertilized egg will have the mutation in each of his or her cells. Somatic mutations occur at some time during a person’s life and are present only in certain cells, not in every cell in the body. These changes can be caused by environmental factors such as ultraviolet radiation from the sun, or can occur if an error is made as DNA copies itself during cell division. Acquired mutations are not usually passed to the next generation.