Unit 5: Heredity Lesson 6: Mutation

Bell Work Who is Gregor Mendel and what did he discover? What day is your test? When are all of your Unit 5 assignments due?

Mutations A mutation is any change in the DNA sequence that causes a change in the amino acid sequence, thus a variation in the protein.

Mutations Mutations can occur many ways: They can be inherited from the parent(s). They can occur in an egg or sperm cell just after fertilization. They can be acquired during the organism’s lifetime.

Are mutations ALWAYS passed on to offspring? Mutations in Gametes Can be passed on to offspring. May result in poorly formed or nonfunctional proteins. May be lethal. Mutations in Somatic Cells Not passed on to offspring. Can interfere with cell function. Due to mitosis, the mutation will be passed on to other cells.

Mutations Two types: Gene Mutations Chromosomal Mutations

Gene Mutations Result from changes in a single gene. Point mutation Occur at a single point.

Point Mutation Example: Change in the Reading Frame Normal Reading Frame: THE FLY HAD ONE RED EYE Point Mutation on Reading Frame: THE FLY HID ONE RED EYE Remember: DNARNAAmino Acidsproteins.

Point Mutation Example: Sickle Cell Anemia Due to a point mutation in the Beta Globin gene. DNA should be C T C but is actually C A C. RNA should be G A G but is actually G U G. This change causes a change in the amino acid. Normal hemoglobin & RBC Sickled hemoglobin & RBC

Gene Mutations Frame-shift Mutation Involves deletions and insertions of nucleotides. Can change the entire reading frame of the gene.

Frameshift Mutation Example: Change in the Reading Frame Normal Reading Frame: THE FLY HAD ONE RED EYE Insertion: THE FLY QHA DON ERE DEY Deletion: THE FLH ADO NER EDE YE Remember DNARNAAmino Acidsproteins. video segment

Chromosomal Mutations Involves changes in the number or structure of chromosomes. May change the locations of genes on the chromosomes and even the number of copies of some. Four types: Deletion Duplication Inversion Translocation

May lead to genetic disorders Nondisjunction May lead to genetic disorders

Klinefelter’s syndrome You have extra sex chromosomes. 47XXY 47XXX 48XXXY 48XXYY 49 XXXXY

Monosomy Having one copy of a chromosome Cri du Chat Syndrome Turner Syndrome

Trisomy Disorders having three copies of a chromosome Down Syndrome is the most recognizable of these, but there are others.

In some cases mutations are beneficial to organisms. Are all mutations bad? In some cases mutations are beneficial to organisms. Beneficial mutations are changes that may be useful to organisms in changing environments. These mutations result in phenotypes that are favored by natural selection and increase in population. Antibiotic resistant bacteria is an example of a beneficial mutation-at least from the point of view from the bacteria.

Bad Mutations Mutations can lead to genetic disorders. By examining a pedigree, geneticists can also see the likelihood of an individual inheriting a genetic disorder.

Review Questions What are the types of gene mutations? What are the types of chromosomal mutations? What is the difference between a chromosomal mutation and a gene mutation?