Mutations

What comes to mind????

Mutants

What are mutations really??? Mutations are changes that occur to the sequence of DNA that also changes the code for a protein...or changes that occur to a gene. Let’s review: –DNA is a nucleic acid. –Therefore, it’s made of nucleotides. –The sequence of the nucleotides (GCAT) is very important because it’s actually a chemical code. –This code is a message or a set of instructions for making proteins. –These proteins end up showing up as an organism’s trait.

Two Types of Mutations 1.Gene Mutation – change that occurs to specific DNA sequence 2.Chromosome Mutation – change that occurs to entire sections of chromosomes

Gene Mutation vs. Chromosome Mutation

Gene Mutations Gene Mutations occur to sequence of DNA Point mutation – single base pair is changed –Substitution Frameshift mutation – shifts the “reading frame” and changes all the codons from the location of the mutation –Insertion –Deletion

Types of Gene Mutations (point) DeletionInsertion (frameshift) Substitution

Point Mutations

Point Mutation Codon is changed Different codon means different amino acid

Gene Mutation - Substitution (point)

Gene Mutation – Deletion (frameshift)

Substitution vs. Deletion

Frameshift Mutations

Insertion vs. Deletion

So, if DNA is a code for making proteins, what if the code changes? If the sequence of DNA is changed, then the message itself is changed. A different set of instructions is sent to the ribosome. The ribosome follows the new set of instructions and assembles/makes a different protein. Different protein could mean a different trait.

Really??? What’s an example??? Sickle Cell Anemia Occurs because of a mutation to the gene that codes for hemoglobin Hemoglobin is a ____________________ In the normal sequence, one nucleotide is changed. ONLY ONE!! The normal sequence has GAG which is a code for the amino acid, Glutamine. The mutant gene has GTG which is a code for the amino acid, Valine. PROTEIN

So... glutamine is replaced with valine... SO WHAT??? Remember, proteins are made of amino acids. More importantly, the sequence of amino acids determine the specific type of protein that’s made. So... all because one nucleotide was switched from adenine (A) to thymine (T), one amino acid was changed and a different protein was produced. Don’t get it??? Go to the next slide.

Because of that “little” change...

Mutation Analogy Original Sentence: THE FAT CAT ATE THE RAT. T The sentence is maintained but there is a change in meaning. The reading frame shifts to the left and the sentence become nonsense. The reading frame shifts to the right and the sentence become nonsense. Substitution: THE FAT CAT ATE THE BAT. Deletion: THE FAT CAA TET HER AT. Insertion: THE FAT CAT SAT ETH ERA T. codon 1codon 2codon 3codon 4codon 5codon 6

Chromosome Mutation Chromosome mutation is a change to the number or structure of chromosomes Four forms of chromosome mutations: Deletion Duplication/Insertion Inversion Translocation

What’s a Chromosome?

Types of Chromosome Mutations AB C DE F AB C DE F AB C DE F AB C DE F A C DE F AED CB F ABC J K LDEF ABB DE F C Deletion Inversion Translocation Duplication/Insertion

Chromosome Mutations

Why do these changes occur? Factors mess up the sequence of DNA = mutagen The changes occur because of –Mistakes during replication –Environment Radiation Chemicals Temperature

What are some examples of mutagens?? Radiation –Nuclear –Gamma –X-ray –Ultra-violet (UV) Chemicals –Dioxins –Benzene –Tobacco (PAHs, nitrosamine, cyanide, arsenic, radioactive polonium... etc.) –Ooze... Just kidding!

Nondisjunction Chromosomes fail to separate during meiosis Offspring have extra sets of chromosomes Polyploidy – condition in which organisms have extra sets of chromosomes Plants that are polyploidy are usually stronger and larger

Polyploidy in Plants

What happens if the mutation occurs in a somatic cell? The altered gene is NOT passed on to the offspring Mutation could impair the function of the cell Mutation could cause cell death Mutation could cause cell to lose its ability to regulate the cell cycle and become cancerous

What happens if a mutation occurs in gametes? The altered gene (code) becomes part of the genetic makeup of the offspring Mutation could produce new trait (very rare) Mutation could be lethal (most common)

What is a positive affect of mutations??? Genetic Diversity

Everyone of us is a MUTANT!