MUTATIONS Where, when, why, and how?

Basic facts A mutation is a change in the genetic code (DNA) of an organism These changes can be to only one nucleotide or to a whole chromosome Some mutations occur naturally, while others can brought on by exposure to something A change in the genetic code can change the amino acid sequence, resulting in a change in the proteins

Types of mutations Nucleotide: TTGTCGTATTG Leucine – Serine – Tyrosine Substitution (aka point mutation) = one base changes into another, may or may not change the amino acid Ex: TTGTCATATTG Leucine – Serine – Tyrosine TTGTCGTATTG Leucine – Serine – Tyrosine

Types of mutations TTGGTCATATTG Leucine – Valine – Isoleucine Frameshift: Insertion = a base is inserted into the DNA code, often changes the amino acid sequence Ex: TTGTCATATTG Leucine – Serine – Tyrosine TTGGTCATATTG Leucine – Valine – Isoleucine Deletion = a base is removed from the DNA sequence, often changes the amino acid sequence -Ex: TTGTCATATTG Leucine – Serine – Tyrosine TTTCATATTG Phenylalanine – Histidine - Isoleucine

Types of mutations Chromosomal: affecting parts of chromosomes Deletion = part is removed Duplication = a part is repeated Inversion = a part is turned upside-down Insertion = a part is added in from another chromosome Translocation = a part is switched to another part of that or another chromosome

Types of mutations Other mutations can occur during the formation of reproductive cells (sperm and egg) When chromosomes don’t separate correctly, the resulting gametes may have more or fewer chromosomes than they’re supposed to This results in the child having more or fewer than 46 chromosomes

Why do mutations occur? Natural reasons: Enzymes like DNA polymerase make a mistake when replicating DNA Enzymes like RNA polymerase make a mistake when copying DNA message Cell age

Why do mutations occur? Induced: Exposure to radioactivity (uranium, etc.) Exposure to UV light Contact with carcinogens (cancer-causing chemicals) Viral infection

How do mutations affect us? Sometimes they don’t have any effect Sometimes they are bad and sometimes they are advantageous

Bad effects Can cause genetic disorders and diseases Ex: Sickle cell anemia Down Syndrome Cancer

Good effects Increases genetic variation in the gene pool Can give the person an advantage or protect them from disease Ex: Sickle Cell Anemia (prevents getting malaria) CCR5 gene mutation (prevents from getting AIDS) Aging associated genes (long life span)

How do we detect mutations? Genetic testing such as DNA sequencing can detect changes in the nucleotides Chromosomal mutations are detected through the use of karyotypes.

Karyotype Chromosomes from the person’s cell are photographed Then the pictures are cut out and the chromosome pairs are matched up More or fewer than 46 indicates a mutation