Chromosomal Gene Mutations What if it’s NOT just the number?

Gene Mutations Damaged Chromosomes – sometimes a portion of a gene or chromosome is lost or damaged during meiosis Gene mutation – a mutation that affects the gene Insertion – one or more nucleotides are added within the DNA sequence Deletion – one or more nucleotides are removed (lost) from the DNA sequence Substitution (point mutation) – an event in which a single nucleotide is replaced with a different nucleotide

Mutations Type Definition Example Insertion A new nucleotide is added …TAGCCAGATA… …TAGCGCAGATA… Deletion A nucleotide is removed (lost) …TAGCAGATA… Substitution (aka Point Mutation) A single nucleotide is replaced with a different nucleotide …TAGCCAGTTA…

Chromosomal Mutation - Deletion Chromosomal mutation – a mutation that affects multiple genes on a chromosome Chromosomal deletion – an event in which a piece of the chromosome is deleted Can remove one or more genes from chromosome

Chromosomal Mutation - Amplification Amplification – a large piece of the chromosome is repeated/duplicated Causes two or more copies of one or more genes

Chromosomal Mutation - Inversion Inversion –one or more nucleotides break off and are flipped over before being reinserted/ reattached Reverses orientation

Chromosomal Mutation - Translocation Translocation is when segments of DNA (nucleotides) move from one chromosome to another chromosome Translocation – one piece of a chromosome is incorrectly inserted into a different chromosome OR when two pieces of different chromosomes are interchanged

Translocation

Effect of Mutations Mutations are ANY change in the DNA sequence! Change to the nucleotide sequence may cause an incorrect polypeptide (protein) to be made Incorrect polypeptide means the protein may not function properly Incorrect sequence = incorrect shape Incorrect shape = incorrect function

Substitution Mutations - Silent Substitution mutations can affect genes in multiple ways Different nucleotide does not always change amino acid used… Silent mutation – a mutation in which there is no effect on the polypeptide chain created No visible affect

Substitution Mutations – Missense Insertion Different nucleotide does not always change amino acid used “Wobble” base! (I’ll explain later!) Missense mutation – a mutation that results in the insertion of a different amino acid May change proteins created

Substitution Mutations - Nonsense Different nucleotide may cause the ribosome to read the codon message incorrectly Nonsense mutation – a mutation in which a “stop codon” is expressed early, creating a shorter polypeptide chain Greatly affects protein created

What the heck is a “codon” anyway? Remember this? Pls txt whn you get a sec Hnd the wrk out ltr Stp whn dun

Frameshift Mutations – VERY BAD! Codons are read “three” nucleotides in a row Insertions and deletions cause frameshift mutations in the reading frame Frameshift mutation – a mutation in which the codon reading frame is changed, potentially changing ALL codons following Since Codons are read in groups of three nucleotides, addition or removal of a nucleotide changes the entire reading frame Different polypeptides produced

Good, Bad or Nothing? Mutations may have an effect on “fitness” (chance of survival) Beneficial mutations – a mutation that increases an organism’s chance of survival (fitness) Fur color may allow organism to better blend into the environment, avoiding predators Harmful mutation – a mutation that decreases an organism’s fitness May make protein used to carry oxygen less efficient Neutral mutation – a mutation that does not affect an organism’s fitness No change in proteins All silent mutations are neutral mutations