MUTATIONS 1B LIVING ENVIRONMENT MURTAUGH

ESSENTIAL QUESTIONS What is a mutation? How is gene mutation and a chromosome mutation different? Do all mutations create a result? What is a karyotype and why is it used? Can mutations be passed on? What causes mutations?

VOCABULARY Mutation: changes in the DNA sequence that affects genetic information. Gene Mutation: a permanent change in the DNA sequence that makes up a gene, can effect one nucleotide or several. Frameshift mutation: changes the amino acid sequence from the site of the mutation. Chromosome Mutation: is a change in the number or structure of chromosomal DNA. Karyotype: the number and visual appearance of the chromosomes in the cell nuclei of an organism or species.

Mutations - changes in the DNA sequence that affects genetic information. Ex) An incorrect base is inserted or a base is skipped as the new strand is “put together” There are two main types of mutations: 1) gene 2) chromosomal

GENE MUTATIONS Most gene mutations involve one nucleotide, but occasionally several are involved. Mutations involving one nucleotide: point mutations 1. One nucleotide is substituted for another, often changing the resulting Amino Acid (A.A.) and usually the protein produced.

GENE MUTATION CONTINUED 2. When a point mutation involves the insertion of an extra, or deletion of an existing nucleotide – how the “code” is read is shifted; this is called a frameshift mutation. **Remember the genetic code is read in groups of three nitrogenous bases (nucleotides) or codons. Result: larger changes in what’s “produced” will occur.

SubstitutionInsertion Deletion Gene Mutations: Substitution, Insertion, and Deletion (frameshift mutations) Go to Section:

CHROMOSOMAL MUTATIONS Chromosomal mutations involve changes in the number or structure of chromosomes.  Changes may include: o locations of genes on chromosomes, o number of copies of genes.

FOUR TYPES OF CHROMOSOMAL MUTATIONS: 1. Deletion: loss of all or part of a chromosome. 2. Duplication: opposite of deletion in which a segment of the chromosome is repeated. 3. Inversion: part of the chromosome gets oriented in reverse of its usual direction. 4. Translocation: part of one chromosome breaks off and attaches to another chromosome.

Duplication Inversion Translocation CHROMOSOMAL MUTATIONS Deletion

TYPES OF GENETIC DISORDERS (CAUSED BY MUTATIONS) Cystic Fibrosis-results when lack of a certain protein is present and the balance of chloride in the body isn’t restricted. Symptoms include difficulty breathing, recurrent lung infections, digestive, and reproductive issues. Severe Combined Immunodeficiency Disorder (SCID)-This disorder is caused by the mutation of more than one gene and renders a person unable to fight off any kind of germs. Tay-Sachs- causes death at any early age, usually around five years old, because of a missing enzyme called Hex-A. Tay-Sachs causes progressive destruction of the nervous system and brain. Huntington’s disease- causes certain nerve cells in the brain and central nervous system to degenerate. Loss of these nerve cells causes symptoms such as behavior changes, unusual, snake-like movements (chorea), uncontrolled movement, difficulty walking, loss of memory, speech and cognitive functions and difficulty in swallowing.

TYPES OF GENETIC DISORDERS (CONTINUED) Sickle Cell Disease- The gene evolved to protect people from malaria. However, getting the gene from both parents, a double dose causes the red blood cells to “sickle” spontaneously during a stress crisis. The sickled cells get stuck in small capillaries and destroy joints and organs. Down Syndrome- caused by the presence of all or part of a third copy of chromosome 21. It is typically associated with physical growth delays, characteristic facial features, and mild to moderate intellectual disability Color-Blindness- the inability or decreased ability to see color, or perceive color differences, under normal lighting conditions. Color blindness affects a significant percentage of the population

KARYOTYPE: A karyotype of an organism is usually displayed in photomicrographs (a picture) where in chromosomes are arranged in homologous pairs, and in descending order of size and relative position of the centromere.

USE OF A KARYOTYPE: A karyotype is used to study: genetic disorders cellular function taxonomic relationships to gather information about past evolutionary events.

DO WE ALWAYS SEE THE MUTATIONS? No, sometimes a mutation is on a gene that is not used. Remember, all cells of an organism are genetically identical (their DNA is exactly the same). What type of cell it depends whether or not a particular gene has been turned “on” or not Sometimes the mutation still codes for the same A.A. which means the same protein is produced.

CAN MUTATIONS BE PASSED ON? ONLY mutations which occur in sex cells or gametes will be frequently be passed on to their offspring.

WHAT CAUSES DNA MUTATIONS? 1. Ultraviolet light (solar radiation/sun), nuclear radiation, X-rays, and chemicals in the environment can damage DNA by altering nucleotide bases so that they look like other nucleotide bases. 2. DNA can get copied wrong during replication or protein synthesis causing big problems like cancer. But remember some mutations cause healthy changes too and lead to evolution of the species.